diff --git a/fftools/ffprobe.c b/fftools/ffprobe.c
index 13ed16431d..7b28f6b3ce 100644
--- a/fftools/ffprobe.c
+++ b/fftools/ffprobe.c
@@ -2158,7 +2158,7 @@ static void show_packet(WriterContext *w, InputFile *ifile, AVPacket *pkt, int p
               pkt->flags & AV_PKT_FLAG_DISCARD ? 'D' : '_');
 
     if (pkt->side_data_elems) {
-        int size;
+        size_t size;
         const uint8_t *side_metadata;
 
         side_metadata = av_packet_get_side_data(pkt, AV_PKT_DATA_STRINGS_METADATA, &size);
diff --git a/libavcodec/aacdec_template.c b/libavcodec/aacdec_template.c
index 98f77a3ad7..d78e60ec2e 100644
--- a/libavcodec/aacdec_template.c
+++ b/libavcodec/aacdec_template.c
@@ -3437,11 +3437,11 @@ static int aac_decode_frame(AVCodecContext *avctx, void *data,
     int buf_consumed;
     int buf_offset;
     int err;
-    buffer_size_t new_extradata_size;
+    size_t new_extradata_size;
     const uint8_t *new_extradata = av_packet_get_side_data(avpkt,
                                        AV_PKT_DATA_NEW_EXTRADATA,
                                        &new_extradata_size);
-    buffer_size_t jp_dualmono_size;
+    size_t jp_dualmono_size;
     const uint8_t *jp_dualmono   = av_packet_get_side_data(avpkt,
                                        AV_PKT_DATA_JP_DUALMONO,
                                        &jp_dualmono_size);
diff --git a/libavcodec/adxdec.c b/libavcodec/adxdec.c
index 94de3eee19..eb05145da9 100644
--- a/libavcodec/adxdec.c
+++ b/libavcodec/adxdec.c
@@ -103,7 +103,7 @@ static int adx_decode_frame(AVCodecContext *avctx, void *data,
     const uint8_t *buf  = avpkt->data;
     const uint8_t *buf_end = buf + avpkt->size;
     int num_blocks, ch, ret;
-    buffer_size_t new_extradata_size;
+    size_t new_extradata_size;
     uint8_t *new_extradata;
 
     new_extradata = av_packet_get_side_data(avpkt, AV_PKT_DATA_NEW_EXTRADATA,
diff --git a/libavcodec/audiotoolboxdec.c b/libavcodec/audiotoolboxdec.c
index fa55f58988..a4fb8c9120 100644
--- a/libavcodec/audiotoolboxdec.c
+++ b/libavcodec/audiotoolboxdec.c
@@ -484,7 +484,7 @@ static int ffat_decode(AVCodecContext *avctx, void *data,
     if (avctx->codec_id == AV_CODEC_ID_AAC) {
         if (!at->extradata_size) {
             uint8_t *side_data;
-            buffer_size_t side_data_size;
+            size_t side_data_size;
 
             side_data = av_packet_get_side_data(avpkt, AV_PKT_DATA_NEW_EXTRADATA,
                                                 &side_data_size);
diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
index 622b50d5eb..e32c467586 100644
--- a/libavcodec/avpacket.c
+++ b/libavcodec/avpacket.c
@@ -218,16 +218,12 @@ int av_packet_add_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
 
 
 uint8_t *av_packet_new_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
-                                 buffer_size_t size)
+                                 size_t size)
 {
     int ret;
     uint8_t *data;
 
-#if FF_API_BUFFER_SIZE_T
-    if ((unsigned)size > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE)
-#else
     if (size > SIZE_MAX - AV_INPUT_BUFFER_PADDING_SIZE)
-#endif
         return NULL;
     data = av_mallocz(size + AV_INPUT_BUFFER_PADDING_SIZE);
     if (!data)
@@ -243,7 +239,7 @@ uint8_t *av_packet_new_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
 }
 
 uint8_t *av_packet_get_side_data(const AVPacket *pkt, enum AVPacketSideDataType type,
-                                 buffer_size_t *size)
+                                 size_t *size)
 {
     int i;
 
@@ -297,11 +293,7 @@ const char *av_packet_side_data_name(enum AVPacketSideDataType type)
     return NULL;
 }
 
-#if FF_API_BUFFER_SIZE_T
-uint8_t *av_packet_pack_dictionary(AVDictionary *dict, int *size)
-#else
 uint8_t *av_packet_pack_dictionary(AVDictionary *dict, size_t *size)
-#endif
 {
     uint8_t *data = NULL;
     *size = 0;
@@ -320,11 +312,7 @@ uint8_t *av_packet_pack_dictionary(AVDictionary *dict, size_t *size)
 
                 if (pass)
                     memcpy(data + total_length, str, len);
-#if FF_API_BUFFER_SIZE_T
-                else if (len > INT_MAX - total_length)
-#else
                 else if (len > SIZE_MAX - total_length)
-#endif
                     return NULL;
                 total_length += len;
             }
@@ -340,12 +328,8 @@ uint8_t *av_packet_pack_dictionary(AVDictionary *dict, size_t *size)
     return data;
 }
 
-#if FF_API_BUFFER_SIZE_T
-int av_packet_unpack_dictionary(const uint8_t *data, int size, AVDictionary **dict)
-#else
 int av_packet_unpack_dictionary(const uint8_t *data, size_t size,
                                 AVDictionary **dict)
-#endif
 {
     const uint8_t *end;
     int ret;
@@ -372,7 +356,7 @@ int av_packet_unpack_dictionary(const uint8_t *data, size_t size,
 }
 
 int av_packet_shrink_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
-                               buffer_size_t size)
+                               size_t size)
 {
     int i;
 
@@ -402,7 +386,7 @@ int av_packet_copy_props(AVPacket *dst, const AVPacket *src)
     dst->side_data_elems      = 0;
     for (i = 0; i < src->side_data_elems; i++) {
         enum AVPacketSideDataType type = src->side_data[i].type;
-        buffer_size_t size = src->side_data[i].size;
+        size_t size = src->side_data[i].size;
         uint8_t *src_data = src->side_data[i].data;
         uint8_t *dst_data = av_packet_new_side_data(dst, type, size);
 
@@ -599,7 +583,7 @@ void avpriv_packet_list_free(PacketList **pkt_buf, PacketList **pkt_buf_end)
 int ff_side_data_set_encoder_stats(AVPacket *pkt, int quality, int64_t *error, int error_count, int pict_type)
 {
     uint8_t *side_data;
-    buffer_size_t side_data_size;
+    size_t side_data_size;
     int i;
 
     side_data = av_packet_get_side_data(pkt, AV_PKT_DATA_QUALITY_STATS, &side_data_size);
@@ -625,7 +609,7 @@ int ff_side_data_set_prft(AVPacket *pkt, int64_t timestamp)
 {
     AVProducerReferenceTime *prft;
     uint8_t *side_data;
-    buffer_size_t side_data_size;
+    size_t side_data_size;
 
     side_data = av_packet_get_side_data(pkt, AV_PKT_DATA_PRFT, &side_data_size);
     if (!side_data) {
diff --git a/libavcodec/cbs_bsf.c b/libavcodec/cbs_bsf.c
index f0f7dd79b5..0977d431f7 100644
--- a/libavcodec/cbs_bsf.c
+++ b/libavcodec/cbs_bsf.c
@@ -24,7 +24,7 @@ static int cbs_bsf_update_side_data(AVBSFContext *bsf, AVPacket *pkt)
     CBSBSFContext           *ctx = bsf->priv_data;
     CodedBitstreamFragment *frag = &ctx->fragment;
     uint8_t *side_data;
-    buffer_size_t side_data_size;
+    size_t side_data_size;
     int err;
 
     side_data = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA,
diff --git a/libavcodec/decode.c b/libavcodec/decode.c
index 9e5230ae1d..cd98c98a97 100644
--- a/libavcodec/decode.c
+++ b/libavcodec/decode.c
@@ -67,7 +67,7 @@ typedef struct FramePool {
 static int apply_param_change(AVCodecContext *avctx, const AVPacket *avpkt)
 {
     int ret;
-    buffer_size_t size;
+    size_t size;
     const uint8_t *data;
     uint32_t flags;
     int64_t val;
@@ -344,7 +344,7 @@ static inline int decode_simple_internal(AVCodecContext *avctx, AVFrame *frame,
             got_frame = 0;
     } else if (avctx->codec->type == AVMEDIA_TYPE_AUDIO) {
         uint8_t *side;
-        buffer_size_t side_size;
+        size_t side_size;
         uint32_t discard_padding = 0;
         uint8_t skip_reason = 0;
         uint8_t discard_reason = 0;
@@ -1463,7 +1463,7 @@ int avcodec_default_get_buffer2(AVCodecContext *avctx, AVFrame *frame, int flags
 
 static int add_metadata_from_side_data(const AVPacket *avpkt, AVFrame *frame)
 {
-    buffer_size_t size;
+    size_t size;
     const uint8_t *side_metadata;
 
     AVDictionary **frame_md = &frame->metadata;
@@ -1502,7 +1502,7 @@ int ff_decode_frame_props(AVCodecContext *avctx, AVFrame *frame)
     frame->pkt_size     = pkt->size;
 
     for (int i = 0; i < FF_ARRAY_ELEMS(sd); i++) {
-        buffer_size_t size;
+        size_t size;
         uint8_t *packet_sd = av_packet_get_side_data(pkt, sd[i].packet, &size);
         if (packet_sd) {
             AVFrameSideData *frame_sd = av_frame_new_side_data(frame,
@@ -1841,14 +1841,15 @@ FF_ENABLE_DEPRECATION_WARNINGS
 
 int ff_copy_palette(void *dst, const AVPacket *src, void *logctx)
 {
-    buffer_size_t size;
+    size_t size;
     const void *pal = av_packet_get_side_data(src, AV_PKT_DATA_PALETTE, &size);
 
     if (pal && size == AVPALETTE_SIZE) {
         memcpy(dst, pal, AVPALETTE_SIZE);
         return 1;
     } else if (pal) {
-        av_log(logctx, AV_LOG_ERROR, "Palette size %d is wrong\n", size);
+        av_log(logctx, AV_LOG_ERROR,
+               "Palette size %"SIZE_SPECIFIER" is wrong\n", size);
     }
     return 0;
 }
diff --git a/libavcodec/h264_metadata_bsf.c b/libavcodec/h264_metadata_bsf.c
index 06d23e3142..ef74cba560 100644
--- a/libavcodec/h264_metadata_bsf.c
+++ b/libavcodec/h264_metadata_bsf.c
@@ -371,7 +371,7 @@ static int h264_metadata_handle_display_orientation(AVBSFContext *bsf,
         H264RawSEIDisplayOrientation *disp =
             &ctx->display_orientation_payload;
         uint8_t *data;
-        buffer_size_t size;
+        size_t size;
         int write = 0;
 
         data = av_packet_get_side_data(pkt, AV_PKT_DATA_DISPLAYMATRIX, &size);
diff --git a/libavcodec/h264dec.c b/libavcodec/h264dec.c
index e5b77abc6a..536020095c 100644
--- a/libavcodec/h264dec.c
+++ b/libavcodec/h264dec.c
@@ -975,7 +975,7 @@ static int h264_decode_frame(AVCodecContext *avctx, void *data,
         return send_next_delayed_frame(h, pict, got_frame, 0);
 
     if (av_packet_get_side_data(avpkt, AV_PKT_DATA_NEW_EXTRADATA, NULL)) {
-        buffer_size_t side_size;
+        size_t side_size;
         uint8_t *side = av_packet_get_side_data(avpkt, AV_PKT_DATA_NEW_EXTRADATA, &side_size);
         ff_h264_decode_extradata(side, side_size,
                                  &h->ps, &h->is_avc, &h->nal_length_size,
diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
index 2231aed259..ad38f37187 100644
--- a/libavcodec/hevcdec.c
+++ b/libavcodec/hevcdec.c
@@ -3303,7 +3303,7 @@ static int hevc_decode_frame(AVCodecContext *avctx, void *data, int *got_output,
                              AVPacket *avpkt)
 {
     int ret;
-    buffer_size_t new_extradata_size;
+    size_t new_extradata_size;
     uint8_t *new_extradata;
     HEVCContext *s = avctx->priv_data;
 
diff --git a/libavcodec/libvpxdec.c b/libavcodec/libvpxdec.c
index 9b5728fba4..67d56fb05e 100644
--- a/libavcodec/libvpxdec.c
+++ b/libavcodec/libvpxdec.c
@@ -221,7 +221,7 @@ static int vpx_decode(AVCodecContext *avctx,
     struct vpx_image *img, *img_alpha;
     int ret;
     uint8_t *side_data = NULL;
-    buffer_size_t side_data_size;
+    size_t side_data_size;
 
     ret = decode_frame(avctx, &ctx->decoder, avpkt->data, avpkt->size);
     if (ret)
diff --git a/libavcodec/mpeg12enc.c b/libavcodec/mpeg12enc.c
index fd3e7de94a..432d27e1f6 100644
--- a/libavcodec/mpeg12enc.c
+++ b/libavcodec/mpeg12enc.c
@@ -575,8 +575,8 @@ void ff_mpeg1_encode_picture_header(MpegEncContext *s, int picture_number)
                 put_bits(&s->pb, 8, 0xff);                  // marker_bits
             } else {
                 av_log(s->avctx, AV_LOG_WARNING,
-                    "Warning Closed Caption size (%d) can not exceed 93 bytes "
-                    "and must be a multiple of 3\n", side_data->size);
+                    "Closed Caption size (%"SIZE_SPECIFIER") can not exceed "
+                    "93 bytes and must be a multiple of 3\n", side_data->size);
             }
         }
     }
diff --git a/libavcodec/mscc.c b/libavcodec/mscc.c
index fe02649623..e685b2a32b 100644
--- a/libavcodec/mscc.c
+++ b/libavcodec/mscc.c
@@ -152,7 +152,7 @@ static int decode_frame(AVCodecContext *avctx,
     }
 
     if (avctx->pix_fmt == AV_PIX_FMT_PAL8) {
-        buffer_size_t size;
+        size_t size;
         const uint8_t *pal = av_packet_get_side_data(avpkt, AV_PKT_DATA_PALETTE, &size);
 
         if (pal && size == AVPALETTE_SIZE) {
@@ -160,7 +160,8 @@ static int decode_frame(AVCodecContext *avctx,
             for (j = 0; j < 256; j++)
                 s->pal[j] = 0xFF000000 | AV_RL32(pal + j * 4);
         } else if (pal) {
-            av_log(avctx, AV_LOG_ERROR, "Palette size %d is wrong\n", size);
+            av_log(avctx, AV_LOG_ERROR,
+                   "Palette size %"SIZE_SPECIFIER" is wrong\n", size);
         }
         memcpy(frame->data[1], s->pal, AVPALETTE_SIZE);
     }
diff --git a/libavcodec/nvdec.c b/libavcodec/nvdec.c
index d6b6608866..251be039a8 100644
--- a/libavcodec/nvdec.c
+++ b/libavcodec/nvdec.c
@@ -242,7 +242,7 @@ fail:
     return ret;
 }
 
-static AVBufferRef *nvdec_decoder_frame_alloc(void *opaque, buffer_size_t size)
+static AVBufferRef *nvdec_decoder_frame_alloc(void *opaque, size_t size)
 {
     NVDECFramePool *pool = opaque;
     AVBufferRef *ret;
@@ -283,7 +283,7 @@ static void nvdec_free_dummy(struct AVHWFramesContext *ctx)
     av_buffer_pool_uninit(&ctx->pool);
 }
 
-static AVBufferRef *nvdec_alloc_dummy(buffer_size_t size)
+static AVBufferRef *nvdec_alloc_dummy(size_t size)
 {
     return av_buffer_create(NULL, 0, NULL, NULL, 0);
 }
diff --git a/libavcodec/packet.h b/libavcodec/packet.h
index 6e6d9c58c9..fad8341c12 100644
--- a/libavcodec/packet.h
+++ b/libavcodec/packet.h
@@ -305,11 +305,7 @@ enum AVPacketSideDataType {
 
 typedef struct AVPacketSideData {
     uint8_t *data;
-#if FF_API_BUFFER_SIZE_T
-    int      size;
-#else
     size_t   size;
-#endif
     enum AVPacketSideDataType type;
 } AVPacketSideData;
 
@@ -528,11 +524,7 @@ int av_packet_from_data(AVPacket *pkt, uint8_t *data, int size);
  * @return pointer to fresh allocated data or NULL otherwise
  */
 uint8_t* av_packet_new_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
-#if FF_API_BUFFER_SIZE_T
-                                 int size);
-#else
                                  size_t size);
-#endif
 
 /**
  * Wrap an existing array as a packet side data.
@@ -559,11 +551,7 @@ int av_packet_add_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
  * @return 0 on success, < 0 on failure
  */
 int av_packet_shrink_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
-#if FF_API_BUFFER_SIZE_T
-                               int size);
-#else
                                size_t size);
-#endif
 
 /**
  * Get side information from packet.
@@ -575,11 +563,7 @@ int av_packet_shrink_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
  * @return pointer to data if present or NULL otherwise
  */
 uint8_t* av_packet_get_side_data(const AVPacket *pkt, enum AVPacketSideDataType type,
-#if FF_API_BUFFER_SIZE_T
-                                 int *size);
-#else
                                  size_t *size);
-#endif
 
 const char *av_packet_side_data_name(enum AVPacketSideDataType type);
 
@@ -590,11 +574,7 @@ const char *av_packet_side_data_name(enum AVPacketSideDataType type);
  * @param size pointer to store the size of the returned data
  * @return pointer to data if successful, NULL otherwise
  */
-#if FF_API_BUFFER_SIZE_T
-uint8_t *av_packet_pack_dictionary(AVDictionary *dict, int *size);
-#else
 uint8_t *av_packet_pack_dictionary(AVDictionary *dict, size_t *size);
-#endif
 /**
  * Unpack a dictionary from side_data.
  *
@@ -603,12 +583,8 @@ uint8_t *av_packet_pack_dictionary(AVDictionary *dict, size_t *size);
  * @param dict the metadata storage dictionary
  * @return 0 on success, < 0 on failure
  */
-#if FF_API_BUFFER_SIZE_T
-int av_packet_unpack_dictionary(const uint8_t *data, int size, AVDictionary **dict);
-#else
 int av_packet_unpack_dictionary(const uint8_t *data, size_t size,
                                 AVDictionary **dict);
-#endif
 
 /**
  * Convenience function to free all the side data stored.
diff --git a/libavcodec/srtdec.c b/libavcodec/srtdec.c
index 98f84ac673..e77b94f74e 100644
--- a/libavcodec/srtdec.c
+++ b/libavcodec/srtdec.c
@@ -59,7 +59,7 @@ static int srt_decode_frame(AVCodecContext *avctx,
     AVBPrint buffer;
     int x1 = -1, y1 = -1, x2 = -1, y2 = -1;
     int ret;
-    buffer_size_t size;
+    size_t size;
     const uint8_t *p = av_packet_get_side_data(avpkt, AV_PKT_DATA_SUBTITLE_POSITION, &size);
     FFASSDecoderContext *s = avctx->priv_data;
 
diff --git a/libavcodec/vaapi_encode.c b/libavcodec/vaapi_encode.c
index 607858435f..7510816ec1 100644
--- a/libavcodec/vaapi_encode.c
+++ b/libavcodec/vaapi_encode.c
@@ -2235,7 +2235,7 @@ static void vaapi_encode_free_output_buffer(void *opaque,
 }
 
 static AVBufferRef *vaapi_encode_alloc_output_buffer(void *opaque,
-                                                     buffer_size_t size)
+                                                     size_t size)
 {
     AVCodecContext   *avctx = opaque;
     VAAPIEncodeContext *ctx = avctx->priv_data;
diff --git a/libavdevice/decklink_dec.cpp b/libavdevice/decklink_dec.cpp
index 79d96cd620..491fe4be3d 100644
--- a/libavdevice/decklink_dec.cpp
+++ b/libavdevice/decklink_dec.cpp
@@ -936,7 +936,7 @@ HRESULT decklink_input_callback::VideoInputFrameArrived(
                         }
 
                         if (av_dict_set(&metadata_dict, "timecode", tc, 0) >= 0) {
-                            buffer_size_t metadata_len;
+                            size_t metadata_len;
                             packed_metadata = av_packet_pack_dictionary(metadata_dict, &metadata_len);
                             av_dict_free(&metadata_dict);
                             if (packed_metadata) {
@@ -1435,7 +1435,7 @@ int ff_decklink_read_packet(AVFormatContext *avctx, AVPacket *pkt)
     avpacket_queue_get(&ctx->queue, pkt, 1);
 
     if (ctx->tc_format && !(av_dict_get(ctx->video_st->metadata, "timecode", NULL, 0))) {
-        buffer_size_t size;
+        size_t size;
         const uint8_t *side_metadata = av_packet_get_side_data(pkt, AV_PKT_DATA_STRINGS_METADATA, &size);
         if (side_metadata) {
            if (av_packet_unpack_dictionary(side_metadata, size, &ctx->video_st->metadata) < 0)
diff --git a/libavdevice/decklink_enc.cpp b/libavdevice/decklink_enc.cpp
index 114c3e1a8c..4c1eb05be4 100644
--- a/libavdevice/decklink_enc.cpp
+++ b/libavdevice/decklink_enc.cpp
@@ -313,7 +313,7 @@ static void construct_cc(AVFormatContext *avctx, struct decklink_ctx *ctx,
     uint16_t *cdp_words;
     uint16_t len;
     uint8_t cc_count;
-    buffer_size_t size;
+    size_t size;
     int ret, i;
 
     const uint8_t *data = av_packet_get_side_data(pkt, AV_PKT_DATA_A53_CC, &size);
diff --git a/libavdevice/lavfi.c b/libavdevice/lavfi.c
index fdadff3f7f..b26d8b739d 100644
--- a/libavdevice/lavfi.c
+++ b/libavdevice/lavfi.c
@@ -446,7 +446,7 @@ static int lavfi_read_packet(AVFormatContext *avctx, AVPacket *pkt)
 
     frame_metadata = frame->metadata;
     if (frame_metadata) {
-        buffer_size_t size;
+        size_t size;
         uint8_t *metadata = av_packet_pack_dictionary(frame_metadata, &size);
 
         if (!metadata) {
diff --git a/libavdevice/xcbgrab.c b/libavdevice/xcbgrab.c
index 8e3292e577..fbe89d472d 100644
--- a/libavdevice/xcbgrab.c
+++ b/libavdevice/xcbgrab.c
@@ -236,7 +236,7 @@ static void free_shm_buffer(void *opaque, uint8_t *data)
     shmdt(data);
 }
 
-static AVBufferRef *allocate_shm_buffer(void *opaque, buffer_size_t size)
+static AVBufferRef *allocate_shm_buffer(void *opaque, size_t size)
 {
     xcb_connection_t *conn = opaque;
     xcb_shm_seg_t segment;
diff --git a/libavfilter/af_ashowinfo.c b/libavfilter/af_ashowinfo.c
index 9046e8d84a..e817ecea37 100644
--- a/libavfilter/af_ashowinfo.c
+++ b/libavfilter/af_ashowinfo.c
@@ -170,7 +170,8 @@ static void dump_audio_service_type(AVFilterContext *ctx, AVFrameSideData *sd)
 
 static void dump_unknown(AVFilterContext *ctx, AVFrameSideData *sd)
 {
-    av_log(ctx, AV_LOG_INFO, "unknown side data type: %d, size %d bytes", sd->type, sd->size);
+    av_log(ctx, AV_LOG_INFO, "unknown side data type: %d, size "
+           "%"SIZE_SPECIFIER" bytes", sd->type, sd->size);
 }
 
 static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
diff --git a/libavfilter/framepool.c b/libavfilter/framepool.c
index 5f67fa170a..9123403c40 100644
--- a/libavfilter/framepool.c
+++ b/libavfilter/framepool.c
@@ -48,7 +48,7 @@ struct FFFramePool {
 
 };
 
-FFFramePool *ff_frame_pool_video_init(AVBufferRef* (*alloc)(buffer_size_t size),
+FFFramePool *ff_frame_pool_video_init(AVBufferRef* (*alloc)(size_t size),
                                       int width,
                                       int height,
                                       enum AVPixelFormat format,
@@ -115,7 +115,7 @@ fail:
     return NULL;
 }
 
-FFFramePool *ff_frame_pool_audio_init(AVBufferRef* (*alloc)(buffer_size_t size),
+FFFramePool *ff_frame_pool_audio_init(AVBufferRef* (*alloc)(size_t size),
                                       int channels,
                                       int nb_samples,
                                       enum AVSampleFormat format,
diff --git a/libavfilter/framepool.h b/libavfilter/framepool.h
index 28857a4a16..daab88e4a5 100644
--- a/libavfilter/framepool.h
+++ b/libavfilter/framepool.h
@@ -44,7 +44,7 @@ typedef struct FFFramePool FFFramePool;
  * @param align buffers alignement of each frame in this pool
  * @return newly created video frame pool on success, NULL on error.
  */
-FFFramePool *ff_frame_pool_video_init(AVBufferRef* (*alloc)(buffer_size_t size),
+FFFramePool *ff_frame_pool_video_init(AVBufferRef* (*alloc)(size_t size),
                                       int width,
                                       int height,
                                       enum AVPixelFormat format,
@@ -62,7 +62,7 @@ FFFramePool *ff_frame_pool_video_init(AVBufferRef* (*alloc)(buffer_size_t size),
  * @param align buffers alignement of each frame in this pool
  * @return newly created audio frame pool on success, NULL on error.
  */
-FFFramePool *ff_frame_pool_audio_init(AVBufferRef* (*alloc)(buffer_size_t size),
+FFFramePool *ff_frame_pool_audio_init(AVBufferRef* (*alloc)(size_t size),
                                       int channels,
                                       int samples,
                                       enum AVSampleFormat format,
diff --git a/libavfilter/vf_showinfo.c b/libavfilter/vf_showinfo.c
index ae6f6bb7b1..2529cb2851 100644
--- a/libavfilter/vf_showinfo.c
+++ b/libavfilter/vf_showinfo.c
@@ -340,7 +340,8 @@ static void dump_sei_unregistered_metadata(AVFilterContext *ctx, const AVFrameSi
     int i;
 
     if (sd->size < uuid_size) {
-        av_log(ctx, AV_LOG_ERROR, "invalid data(%d < UUID(%d-bytes))\n", sd->size, uuid_size);
+        av_log(ctx, AV_LOG_ERROR, "invalid data(%"SIZE_SPECIFIER" < "
+               "UUID(%d-bytes))\n", sd->size, uuid_size);
         return;
     }
 
@@ -498,7 +499,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
             av_log(ctx, AV_LOG_INFO, "pan/scan");
             break;
         case AV_FRAME_DATA_A53_CC:
-            av_log(ctx, AV_LOG_INFO, "A/53 closed captions (%d bytes)", sd->size);
+            av_log(ctx, AV_LOG_INFO, "A/53 closed captions "
+                   "(%"SIZE_SPECIFIER" bytes)", sd->size);
             break;
         case AV_FRAME_DATA_SPHERICAL:
             dump_spherical(ctx, frame, sd);
@@ -545,8 +547,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
             dump_sei_unregistered_metadata(ctx, sd);
             break;
         default:
-            av_log(ctx, AV_LOG_WARNING, "unknown side data type %d (%d bytes)\n",
-                   sd->type, sd->size);
+            av_log(ctx, AV_LOG_WARNING, "unknown side data type %d "
+                   "(%"SIZE_SPECIFIER" bytes)\n", sd->type, sd->size);
             break;
         }
 
diff --git a/libavformat/adtsenc.c b/libavformat/adtsenc.c
index 3595cb3bb2..14214eb0b9 100644
--- a/libavformat/adtsenc.c
+++ b/libavformat/adtsenc.c
@@ -170,7 +170,7 @@ static int adts_write_packet(AVFormatContext *s, AVPacket *pkt)
         return 0;
     if (!par->extradata_size) {
         uint8_t *side_data;
-        buffer_size_t side_data_size;
+        size_t side_data_size;
         int ret;
 
         side_data = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA,
diff --git a/libavformat/apngenc.c b/libavformat/apngenc.c
index 7e86f45143..643bf73300 100644
--- a/libavformat/apngenc.c
+++ b/libavformat/apngenc.c
@@ -119,7 +119,7 @@ static int flush_packet(AVFormatContext *format_context, AVPacket *packet)
     AVIOContext *io_context = format_context->pb;
     AVStream *codec_stream = format_context->streams[0];
     uint8_t *side_data = NULL;
-    buffer_size_t side_data_size;
+    size_t side_data_size;
 
     av_assert0(apng->prev_packet);
 
diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index bb8ddef88d..3834c9869f 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1873,11 +1873,7 @@ int av_stream_add_side_data(AVStream *st, enum AVPacketSideDataType type,
  * @return pointer to fresh allocated data or NULL otherwise
  */
 uint8_t *av_stream_new_side_data(AVStream *stream,
-#if FF_API_BUFFER_SIZE_T
-                                 enum AVPacketSideDataType type, int size);
-#else
                                  enum AVPacketSideDataType type, size_t size);
-#endif
 /**
  * Get side information from stream.
  *
@@ -1888,11 +1884,7 @@ uint8_t *av_stream_new_side_data(AVStream *stream,
  * @return pointer to data if present or NULL otherwise
  */
 uint8_t *av_stream_get_side_data(const AVStream *stream,
-#if FF_API_BUFFER_SIZE_T
-                                 enum AVPacketSideDataType type, int *size);
-#else
                                  enum AVPacketSideDataType type, size_t *size);
-#endif
 
 AVProgram *av_new_program(AVFormatContext *s, int id);
 
diff --git a/libavformat/concatdec.c b/libavformat/concatdec.c
index 32d4a99010..fb70c21dc2 100644
--- a/libavformat/concatdec.c
+++ b/libavformat/concatdec.c
@@ -626,7 +626,7 @@ static int concat_read_packet(AVFormatContext *avf, AVPacket *pkt)
            av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, &st->time_base),
            av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, &st->time_base));
     if (cat->cur_file->metadata) {
-        buffer_size_t metadata_len;
+        size_t metadata_len;
         char* packed_metadata = av_packet_pack_dictionary(cat->cur_file->metadata, &metadata_len);
         if (!packed_metadata)
             return AVERROR(ENOMEM);
diff --git a/libavformat/dashenc.c b/libavformat/dashenc.c
index a73fa60d2a..0ceaa5fdfd 100644
--- a/libavformat/dashenc.c
+++ b/libavformat/dashenc.c
@@ -1806,7 +1806,7 @@ static int update_stream_extradata(AVFormatContext *s, OutputStream *os,
 {
     AVCodecParameters *par = os->ctx->streams[0]->codecpar;
     uint8_t *extradata;
-    buffer_size_t extradata_size;
+    size_t extradata_size;
     int ret;
 
     if (par->extradata_size)
@@ -2022,7 +2022,7 @@ static int dash_parse_prft(DASHContext *c, AVPacket *pkt)
 {
     OutputStream *os = &c->streams[pkt->stream_index];
     AVProducerReferenceTime *prft;
-    buffer_size_t side_data_size;
+    size_t side_data_size;
 
     prft = (AVProducerReferenceTime *)av_packet_get_side_data(pkt, AV_PKT_DATA_PRFT, &side_data_size);
     if (!prft || side_data_size != sizeof(AVProducerReferenceTime) || (prft->flags && prft->flags != 24)) {
diff --git a/libavformat/dump.c b/libavformat/dump.c
index 2b6ed1ed1f..a520b01e2d 100644
--- a/libavformat/dump.c
+++ b/libavformat/dump.c
@@ -491,8 +491,8 @@ static void dump_sidedata(void *ctx, const AVStream *st, const char *indent)
             dump_s12m_timecode(ctx, st, sd);
             break;
         default:
-            av_log(ctx, AV_LOG_INFO,
-                   "unknown side data type %d (%d bytes)", sd->type, sd->size);
+            av_log(ctx, AV_LOG_INFO, "unknown side data type %d "
+                   "(%"SIZE_SPECIFIER" bytes)", sd->type, sd->size);
             break;
         }
 
diff --git a/libavformat/flacenc.c b/libavformat/flacenc.c
index 57f5c012f7..cdd25b817f 100644
--- a/libavformat/flacenc.c
+++ b/libavformat/flacenc.c
@@ -280,7 +280,7 @@ static int flac_write_audio_packet(struct AVFormatContext *s, AVPacket *pkt)
 {
     FlacMuxerContext *c = s->priv_data;
     uint8_t *streaminfo;
-    buffer_size_t streaminfo_size;
+    size_t streaminfo_size;
 
     /* check for updated streaminfo */
     streaminfo = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA,
diff --git a/libavformat/flvenc.c b/libavformat/flvenc.c
index 35bf7ace5e..711b94c5bc 100644
--- a/libavformat/flvenc.c
+++ b/libavformat/flvenc.c
@@ -902,7 +902,7 @@ static int flv_write_packet(AVFormatContext *s, AVPacket *pkt)
 
     if (par->codec_id == AV_CODEC_ID_AAC || par->codec_id == AV_CODEC_ID_H264
             || par->codec_id == AV_CODEC_ID_MPEG4) {
-        buffer_size_t side_size;
+        size_t side_size;
         uint8_t *side = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA, &side_size);
         if (side && side_size > 0 && (side_size != par->extradata_size || memcmp(side, par->extradata, side_size))) {
             ret = ff_alloc_extradata(par, side_size);
diff --git a/libavformat/framecrcenc.c b/libavformat/framecrcenc.c
index 1fbe4aa4ee..4e62049305 100644
--- a/libavformat/framecrcenc.c
+++ b/libavformat/framecrcenc.c
@@ -88,7 +88,7 @@ static int framecrc_write_packet(struct AVFormatContext *s, AVPacket *pkt)
             case AV_PKT_DATA_SPHERICAL:
             case AV_PKT_DATA_CONTENT_LIGHT_LEVEL:
             case AV_PKT_DATA_S12M_TIMECODE:
-                for (int j = 0; j < sd->size / 4; j++) {
+                for (size_t j = 0; j < sd->size / 4; j++) {
                     uint8_t buf[4];
                     AV_WL32(buf, AV_RB32(sd->data + 4 * j));
                     side_data_crc = av_adler32_update(side_data_crc, buf, 4);
@@ -119,7 +119,9 @@ static int framecrc_write_packet(struct AVFormatContext *s, AVPacket *pkt)
             default:
                 side_data_crc = av_adler32_update(0, data, sd->size);
             }
-            av_strlcatf(buf, sizeof(buf), ", %8d, 0x%08"PRIx32, pkt->side_data[i].size, side_data_crc);
+
+            av_strlcatf(buf, sizeof(buf), ", %8"SIZE_SPECIFIER", 0x%08"PRIx32,
+                        pkt->side_data[i].size, side_data_crc);
         }
     }
     av_strlcatf(buf, sizeof(buf), "\n");
diff --git a/libavformat/hashenc.c b/libavformat/hashenc.c
index 1e9faf372a..ec4e44ef12 100644
--- a/libavformat/hashenc.c
+++ b/libavformat/hashenc.c
@@ -298,18 +298,19 @@ static int framehash_write_packet(struct AVFormatContext *s, AVPacket *pkt)
     avio_write(s->pb, buf, strlen(buf));
 
     if (c->format_version > 1 && pkt->side_data_elems) {
-        int i, j;
+        int i;
         avio_printf(s->pb, ", S=%d", pkt->side_data_elems);
         for (i = 0; i < pkt->side_data_elems; i++) {
             av_hash_init(c->hashes[0]);
             if (HAVE_BIGENDIAN && pkt->side_data[i].type == AV_PKT_DATA_PALETTE) {
-                for (j = 0; j < pkt->side_data[i].size; j += sizeof(uint32_t)) {
+                for (size_t j = 0; j < pkt->side_data[i].size; j += sizeof(uint32_t)) {
                     uint32_t data = AV_RL32(pkt->side_data[i].data + j);
                     av_hash_update(c->hashes[0], (uint8_t *)&data, sizeof(uint32_t));
                 }
             } else
                 av_hash_update(c->hashes[0], pkt->side_data[i].data, pkt->side_data[i].size);
-            snprintf(buf, sizeof(buf) - (AV_HASH_MAX_SIZE * 2 + 1), ", %8d, ", pkt->side_data[i].size);
+            snprintf(buf, sizeof(buf) - (AV_HASH_MAX_SIZE * 2 + 1),
+                     ", %8"SIZE_SPECIFIER", ", pkt->side_data[i].size);
             len = strlen(buf);
             av_hash_final_hex(c->hashes[0], buf + len, sizeof(buf) - len);
             avio_write(s->pb, buf, strlen(buf));
diff --git a/libavformat/img2dec.c b/libavformat/img2dec.c
index 7b03cb2af1..84ce9ea093 100644
--- a/libavformat/img2dec.c
+++ b/libavformat/img2dec.c
@@ -383,7 +383,7 @@ int ff_img_read_header(AVFormatContext *s1)
 static int add_filename_as_pkt_side_data(char *filename, AVPacket *pkt) {
     AVDictionary *d = NULL;
     char *packed_metadata = NULL;
-    buffer_size_t metadata_len;
+    size_t metadata_len;
     int ret;
 
     av_dict_set(&d, "lavf.image2dec.source_path", filename, 0);
diff --git a/libavformat/latmenc.c b/libavformat/latmenc.c
index 5488361bde..80fd2dfe27 100644
--- a/libavformat/latmenc.c
+++ b/libavformat/latmenc.c
@@ -176,7 +176,7 @@ static int latm_write_packet(AVFormatContext *s, AVPacket *pkt)
             return ff_raw_write_packet(s, pkt);
         else {
             uint8_t *side_data;
-            buffer_size_t side_data_size;
+            size_t side_data_size;
             int ret;
 
             side_data = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA,
diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index c3d895f931..5ac4db458b 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -2030,7 +2030,7 @@ static int mkv_write_block(AVFormatContext *s, AVIOContext *pb,
     AVCodecParameters *par = s->streams[pkt->stream_index]->codecpar;
     mkv_track *track = &mkv->tracks[pkt->stream_index];
     uint8_t *data = NULL, *side_data = NULL;
-    buffer_size_t side_data_size;
+    size_t side_data_size;
     int err = 0, offset = 0, size = pkt->size;
     int64_t ts = track->write_dts ? pkt->dts : pkt->pts;
     uint64_t additional_id;
@@ -2141,7 +2141,7 @@ static int mkv_write_vtt_blocks(AVFormatContext *s, AVIOContext *pb, const AVPac
     MatroskaMuxContext *mkv = s->priv_data;
     mkv_track *track = &mkv->tracks[pkt->stream_index];
     ebml_master blockgroup;
-    buffer_size_t id_size, settings_size;
+    size_t id_size, settings_size;
     int size, id_size_int, settings_size_int;
     const char *id, *settings;
     int64_t ts = track->write_dts ? pkt->dts : pkt->pts;
@@ -2214,7 +2214,7 @@ static int mkv_check_new_extra_data(AVFormatContext *s, const AVPacket *pkt)
     mkv_track *track        = &mkv->tracks[pkt->stream_index];
     AVCodecParameters *par  = s->streams[pkt->stream_index]->codecpar;
     uint8_t *side_data;
-    buffer_size_t side_data_size;
+    size_t side_data_size;
     int ret;
 
     side_data = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA,
diff --git a/libavformat/mov.c b/libavformat/mov.c
index 8b3371abe6..77ab45aa61 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -6362,8 +6362,7 @@ static int mov_read_pssh(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     uint8_t **key_ids;
     AVStream *st;
     uint8_t *side_data, *extra_data, *old_side_data;
-    size_t side_data_size;
-    buffer_size_t old_side_data_size;
+    size_t side_data_size, old_side_data_size;
     int ret = 0;
     unsigned int version, kid_count, extra_data_size, alloc_size = 0;
 
diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index b15ecbe713..a315377ef6 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -1992,7 +1992,7 @@ static int mov_write_colr_tag(AVIOContext *pb, MOVTrack *track, int prefer_icc)
     // Ref (MP4): ISO/IEC 14496-12:2012
 
     const uint8_t *icc_profile;
-    buffer_size_t icc_profile_size;
+    size_t icc_profile_size;
 
     if (prefer_icc) {
         icc_profile = av_stream_get_side_data(track->st, AV_PKT_DATA_ICC_PROFILE, &icc_profile_size);
@@ -3046,7 +3046,7 @@ static int mov_write_tkhd_tag(AVIOContext *pb, MOVMuxContext *mov,
     int group   = 0;
 
     uint32_t *display_matrix = NULL;
-    buffer_size_t display_matrix_size;
+    size_t display_matrix_size;
     int       i;
 
     if (st) {
@@ -4173,7 +4173,7 @@ static int mov_write_moov_tag(AVIOContext *pb, MOVMuxContext *mov,
             track->tref_tag = MKTAG('h','i','n','t');
             track->tref_id = mov->tracks[track->src_track].track_id;
         } else if (track->par->codec_type == AVMEDIA_TYPE_AUDIO) {
-            buffer_size_t size;
+            size_t size;
             int *fallback;
             fallback = (int*)av_stream_get_side_data(track->st,
                                                      AV_PKT_DATA_FALLBACK_TRACK,
@@ -5557,7 +5557,7 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt)
     AVProducerReferenceTime *prft;
     unsigned int samples_in_chunk = 0;
     int size = pkt->size, ret = 0, offset = 0;
-    buffer_size_t prft_size;
+    size_t prft_size;
     uint8_t *reformatted_data = NULL;
 
     ret = check_pkt(s, pkt);
@@ -5910,7 +5910,7 @@ static int mov_write_single_packet(AVFormatContext *s, AVPacket *pkt)
             trk->par->codec_id == AV_CODEC_ID_AAC ||
             trk->par->codec_id == AV_CODEC_ID_AV1 ||
             trk->par->codec_id == AV_CODEC_ID_FLAC) {
-        buffer_size_t side_size;
+        size_t side_size;
         uint8_t *side = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA, &side_size);
         if (side && side_size > 0 && (side_size != par->extradata_size || memcmp(side, par->extradata, side_size))) {
             void *newextra = av_mallocz(side_size + AV_INPUT_BUFFER_PADDING_SIZE);
diff --git a/libavformat/mp3enc.c b/libavformat/mp3enc.c
index 803148f0c8..6607560086 100644
--- a/libavformat/mp3enc.c
+++ b/libavformat/mp3enc.c
@@ -355,7 +355,7 @@ static int mp3_write_audio_packet(AVFormatContext *s, AVPacket *pkt)
 
         if (mp3->xing_offset) {
             uint8_t *side_data = NULL;
-            buffer_size_t side_data_size;
+            size_t side_data_size;
 
             mp3_xing_add_frame(mp3, pkt);
             mp3->audio_size += pkt->size;
@@ -402,7 +402,7 @@ static void mp3_update_xing(AVFormatContext *s)
     AVReplayGain *rg;
     uint16_t tag_crc;
     uint8_t *toc;
-    buffer_size_t rg_size;
+    size_t rg_size;
     int i;
     int64_t old_pos = avio_tell(s->pb);
 
diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c
index a357f3a6aa..51da325e90 100644
--- a/libavformat/mpegtsenc.c
+++ b/libavformat/mpegtsenc.c
@@ -1681,7 +1681,7 @@ static int mpegts_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
     const int64_t max_audio_delay = av_rescale(s->max_delay, 90000, AV_TIME_BASE) / 2;
     int64_t dts = pkt->dts, pts = pkt->pts;
     int opus_samples = 0;
-    buffer_size_t side_data_size;
+    size_t side_data_size;
     uint8_t *side_data = NULL;
     int stream_id = -1;
 
@@ -1818,7 +1818,7 @@ static int mpegts_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
         /* Add Opus control header */
         if ((AV_RB16(pkt->data) >> 5) != 0x3ff) {
             uint8_t *side_data;
-            buffer_size_t side_data_size;
+            size_t side_data_size;
             int i, n;
             int ctrl_header_size;
             int trim_start = 0, trim_end = 0;
diff --git a/libavformat/oggdec.h b/libavformat/oggdec.h
index bf982bfe1c..4cce53de41 100644
--- a/libavformat/oggdec.h
+++ b/libavformat/oggdec.h
@@ -87,7 +87,7 @@ struct ogg_stream {
     int start_trimming; ///< set the number of packets to drop from the start
     int end_trimming; ///< set the number of packets to drop from the end
     uint8_t *new_metadata;
-    buffer_size_t new_metadata_size;
+    size_t new_metadata_size;
     void *private;
 };
 
diff --git a/libavformat/rtpenc.c b/libavformat/rtpenc.c
index 38e4c65c4e..557128ce53 100644
--- a/libavformat/rtpenc.c
+++ b/libavformat/rtpenc.c
@@ -589,7 +589,7 @@ static int rtp_write_packet(AVFormatContext *s1, AVPacket *pkt)
         break;
     case AV_CODEC_ID_H263:
         if (s->flags & FF_RTP_FLAG_RFC2190) {
-            buffer_size_t mb_info_size;
+            size_t mb_info_size;
             const uint8_t *mb_info =
                 av_packet_get_side_data(pkt, AV_PKT_DATA_H263_MB_INFO,
                                         &mb_info_size);
diff --git a/libavformat/segment.c b/libavformat/segment.c
index 13954b8f99..faa8eb8f92 100644
--- a/libavformat/segment.c
+++ b/libavformat/segment.c
@@ -856,7 +856,7 @@ static int seg_write_packet(AVFormatContext *s, AVPacket *pkt)
         return AVERROR(EINVAL);
 
     if (!st->codecpar->extradata_size) {
-        buffer_size_t pkt_extradata_size;
+        size_t pkt_extradata_size;
         uint8_t *pkt_extradata = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA, &pkt_extradata_size);
         if (pkt_extradata && pkt_extradata_size > 0) {
             ret = ff_alloc_extradata(st->codecpar, pkt_extradata_size);
diff --git a/libavformat/srtenc.c b/libavformat/srtenc.c
index 9bb0ff94c1..93d5ed7ac8 100644
--- a/libavformat/srtenc.c
+++ b/libavformat/srtenc.c
@@ -61,7 +61,7 @@ static int srt_write_packet(AVFormatContext *avf, AVPacket *pkt)
     SRTContext *srt = avf->priv_data;
 
     int64_t s = pkt->pts, e, d = pkt->duration;
-    buffer_size_t size;
+    size_t size;
     int x1 = -1, y1 = -1, x2 = -1, y2 = -1;
     const uint8_t *p;
 
diff --git a/libavformat/utils.c b/libavformat/utils.c
index e36b75081f..7078891dc0 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -5462,7 +5462,7 @@ int ff_generate_avci_extradata(AVStream *st)
 }
 
 uint8_t *av_stream_get_side_data(const AVStream *st,
-                                 enum AVPacketSideDataType type, buffer_size_t *size)
+                                 enum AVPacketSideDataType type, size_t *size)
 {
     int i;
 
@@ -5515,7 +5515,7 @@ int av_stream_add_side_data(AVStream *st, enum AVPacketSideDataType type,
 }
 
 uint8_t *av_stream_new_side_data(AVStream *st, enum AVPacketSideDataType type,
-                                 buffer_size_t size)
+                                 size_t size)
 {
     int ret;
     uint8_t *data = av_malloc(size);
@@ -5631,7 +5631,7 @@ int ff_standardize_creation_time(AVFormatContext *s)
 int ff_get_packet_palette(AVFormatContext *s, AVPacket *pkt, int ret, uint32_t *palette)
 {
     uint8_t *side_data;
-    buffer_size_t size;
+    size_t size;
 
     side_data = av_packet_get_side_data(pkt, AV_PKT_DATA_PALETTE, &size);
     if (side_data) {
diff --git a/libavformat/webvttdec.c b/libavformat/webvttdec.c
index 8d2fdfed37..cf060bd011 100644
--- a/libavformat/webvttdec.c
+++ b/libavformat/webvttdec.c
@@ -78,7 +78,7 @@ static int webvtt_read_header(AVFormatContext *s)
         int64_t pos;
         AVPacket *sub;
         const char *p, *identifier, *settings;
-        int identifier_len, settings_len;
+        size_t identifier_len, settings_len;
         int64_t ts_start, ts_end;
 
         ff_subtitles_read_chunk(s->pb, &cue);
diff --git a/libavformat/webvttenc.c b/libavformat/webvttenc.c
index 2bc86041a7..95f58e2942 100644
--- a/libavformat/webvttenc.c
+++ b/libavformat/webvttenc.c
@@ -64,7 +64,7 @@ static int webvtt_write_header(AVFormatContext *ctx)
 static int webvtt_write_packet(AVFormatContext *ctx, AVPacket *pkt)
 {
     AVIOContext  *pb = ctx->pb;
-    buffer_size_t id_size, settings_size;
+    size_t id_size, settings_size;
     int id_size_int, settings_size_int;
     uint8_t *id, *settings;
 
diff --git a/libavutil/buffer.c b/libavutil/buffer.c
index 858633e8c7..b13eeadffb 100644
--- a/libavutil/buffer.c
+++ b/libavutil/buffer.c
@@ -26,7 +26,7 @@
 #include "mem.h"
 #include "thread.h"
 
-AVBufferRef *av_buffer_create(uint8_t *data, buffer_size_t size,
+AVBufferRef *av_buffer_create(uint8_t *data, size_t size,
                               void (*free)(void *opaque, uint8_t *data),
                               void *opaque, int flags)
 {
@@ -64,7 +64,7 @@ void av_buffer_default_free(void *opaque, uint8_t *data)
     av_free(data);
 }
 
-AVBufferRef *av_buffer_alloc(buffer_size_t size)
+AVBufferRef *av_buffer_alloc(size_t size)
 {
     AVBufferRef *ret = NULL;
     uint8_t    *data = NULL;
@@ -80,7 +80,7 @@ AVBufferRef *av_buffer_alloc(buffer_size_t size)
     return ret;
 }
 
-AVBufferRef *av_buffer_allocz(buffer_size_t size)
+AVBufferRef *av_buffer_allocz(size_t size)
 {
     AVBufferRef *ret = av_buffer_alloc(size);
     if (!ret)
@@ -166,7 +166,7 @@ int av_buffer_make_writable(AVBufferRef **pbuf)
     return 0;
 }
 
-int av_buffer_realloc(AVBufferRef **pbuf, buffer_size_t size)
+int av_buffer_realloc(AVBufferRef **pbuf, size_t size)
 {
     AVBufferRef *buf = *pbuf;
     uint8_t *tmp;
@@ -242,8 +242,8 @@ int av_buffer_replace(AVBufferRef **pdst, AVBufferRef *src)
     return 0;
 }
 
-AVBufferPool *av_buffer_pool_init2(buffer_size_t size, void *opaque,
-                                   AVBufferRef* (*alloc)(void *opaque, buffer_size_t size),
+AVBufferPool *av_buffer_pool_init2(size_t size, void *opaque,
+                                   AVBufferRef* (*alloc)(void *opaque, size_t size),
                                    void (*pool_free)(void *opaque))
 {
     AVBufferPool *pool = av_mallocz(sizeof(*pool));
@@ -263,7 +263,7 @@ AVBufferPool *av_buffer_pool_init2(buffer_size_t size, void *opaque,
     return pool;
 }
 
-AVBufferPool *av_buffer_pool_init(buffer_size_t size, AVBufferRef* (*alloc)(buffer_size_t size))
+AVBufferPool *av_buffer_pool_init(size_t size, AVBufferRef* (*alloc)(size_t size))
 {
     AVBufferPool *pool = av_mallocz(sizeof(*pool));
     if (!pool)
diff --git a/libavutil/buffer.h b/libavutil/buffer.h
index 241a80ed67..63ab87eb72 100644
--- a/libavutil/buffer.h
+++ b/libavutil/buffer.h
@@ -93,11 +93,7 @@ typedef struct AVBufferRef {
     /**
      * Size of data in bytes.
      */
-#if FF_API_BUFFER_SIZE_T
-    int      size;
-#else
     size_t   size;
-#endif
 } AVBufferRef;
 
 /**
@@ -105,21 +101,13 @@ typedef struct AVBufferRef {
  *
  * @return an AVBufferRef of given size or NULL when out of memory
  */
-#if FF_API_BUFFER_SIZE_T
-AVBufferRef *av_buffer_alloc(int size);
-#else
 AVBufferRef *av_buffer_alloc(size_t size);
-#endif
 
 /**
  * Same as av_buffer_alloc(), except the returned buffer will be initialized
  * to zero.
  */
-#if FF_API_BUFFER_SIZE_T
-AVBufferRef *av_buffer_allocz(int size);
-#else
 AVBufferRef *av_buffer_allocz(size_t size);
-#endif
 
 /**
  * Always treat the buffer as read-only, even when it has only one
@@ -142,11 +130,7 @@ AVBufferRef *av_buffer_allocz(size_t size);
  *
  * @return an AVBufferRef referring to data on success, NULL on failure.
  */
-#if FF_API_BUFFER_SIZE_T
-AVBufferRef *av_buffer_create(uint8_t *data, int size,
-#else
 AVBufferRef *av_buffer_create(uint8_t *data, size_t size,
-#endif
                               void (*free)(void *opaque, uint8_t *data),
                               void *opaque, int flags);
 
@@ -214,11 +198,7 @@ int av_buffer_make_writable(AVBufferRef **buf);
  * reference to it (i.e. the one passed to this function). In all other cases
  * a new buffer is allocated and the data is copied.
  */
-#if FF_API_BUFFER_SIZE_T
-int av_buffer_realloc(AVBufferRef **buf, int size);
-#else
 int av_buffer_realloc(AVBufferRef **buf, size_t size);
-#endif
 
 /**
  * Ensure dst refers to the same data as src.
@@ -285,11 +265,7 @@ typedef struct AVBufferPool AVBufferPool;
  * (av_buffer_alloc()).
  * @return newly created buffer pool on success, NULL on error.
  */
-#if FF_API_BUFFER_SIZE_T
-AVBufferPool *av_buffer_pool_init(int size, AVBufferRef* (*alloc)(int size));
-#else
 AVBufferPool *av_buffer_pool_init(size_t size, AVBufferRef* (*alloc)(size_t size));
-#endif
 
 /**
  * Allocate and initialize a buffer pool with a more complex allocator.
@@ -306,13 +282,8 @@ AVBufferPool *av_buffer_pool_init(size_t size, AVBufferRef* (*alloc)(size_t size
  *                  data. May be NULL.
  * @return newly created buffer pool on success, NULL on error.
  */
-#if FF_API_BUFFER_SIZE_T
-AVBufferPool *av_buffer_pool_init2(int size, void *opaque,
-                                   AVBufferRef* (*alloc)(void *opaque, int size),
-#else
 AVBufferPool *av_buffer_pool_init2(size_t size, void *opaque,
                                    AVBufferRef* (*alloc)(void *opaque, size_t size),
-#endif
                                    void (*pool_free)(void *opaque));
 
 /**
diff --git a/libavutil/buffer_internal.h b/libavutil/buffer_internal.h
index d902772ed3..839dc05f8f 100644
--- a/libavutil/buffer_internal.h
+++ b/libavutil/buffer_internal.h
@@ -33,7 +33,7 @@
 
 struct AVBuffer {
     uint8_t *data; /**< data described by this buffer */
-    buffer_size_t size; /**< size of data in bytes */
+    size_t size; /**< size of data in bytes */
 
     /**
      *  number of existing AVBufferRef instances referring to this buffer
@@ -90,10 +90,10 @@ struct AVBufferPool {
      */
     atomic_uint refcount;
 
-    buffer_size_t size;
+    size_t size;
     void *opaque;
-    AVBufferRef* (*alloc)(buffer_size_t size);
-    AVBufferRef* (*alloc2)(void *opaque, buffer_size_t size);
+    AVBufferRef* (*alloc)(size_t size);
+    AVBufferRef* (*alloc2)(void *opaque, size_t size);
     void         (*pool_free)(void *opaque);
 };
 
diff --git a/libavutil/detection_bbox.c b/libavutil/detection_bbox.c
index 0750ffac6a..40711e6aa9 100644
--- a/libavutil/detection_bbox.c
+++ b/libavutil/detection_bbox.c
@@ -54,10 +54,6 @@ AVDetectionBBoxHeader *av_detection_bbox_create_side_data(AVFrame *frame, uint32
     header = av_detection_bbox_alloc(nb_bboxes, &size);
     if (!header)
         return NULL;
-    if (size > INT_MAX) {
-        av_freep(&header);
-        return NULL;
-    }
     buf = av_buffer_create((uint8_t *)header, size, NULL, NULL, 0);
     if (!buf) {
         av_freep(&header);
diff --git a/libavutil/frame.c b/libavutil/frame.c
index 5bc8ab36df..2ec59b44b1 100644
--- a/libavutil/frame.c
+++ b/libavutil/frame.c
@@ -603,7 +603,7 @@ AVFrameSideData *av_frame_new_side_data_from_buf(AVFrame *frame,
 
 AVFrameSideData *av_frame_new_side_data(AVFrame *frame,
                                         enum AVFrameSideDataType type,
-                                        buffer_size_t size)
+                                        size_t size)
 {
     AVFrameSideData *ret;
     AVBufferRef *buf = av_buffer_alloc(size);
diff --git a/libavutil/frame.h b/libavutil/frame.h
index 853d4cabec..ff2540a20f 100644
--- a/libavutil/frame.h
+++ b/libavutil/frame.h
@@ -209,11 +209,7 @@ enum AVActiveFormatDescription {
 typedef struct AVFrameSideData {
     enum AVFrameSideDataType type;
     uint8_t *data;
-#if FF_API_BUFFER_SIZE_T
-    int      size;
-#else
     size_t   size;
-#endif
     AVDictionary *metadata;
     AVBufferRef *buf;
 } AVFrameSideData;
@@ -818,11 +814,7 @@ AVBufferRef *av_frame_get_plane_buffer(AVFrame *frame, int plane);
  */
 AVFrameSideData *av_frame_new_side_data(AVFrame *frame,
                                         enum AVFrameSideDataType type,
-#if FF_API_BUFFER_SIZE_T
-                                        int size);
-#else
                                         size_t size);
-#endif
 
 /**
  * Add a new side data to a frame from an existing AVBufferRef
diff --git a/libavutil/hwcontext_cuda.c b/libavutil/hwcontext_cuda.c
index 3773cd9eb8..cfdf2d7fd4 100644
--- a/libavutil/hwcontext_cuda.c
+++ b/libavutil/hwcontext_cuda.c
@@ -93,7 +93,7 @@ static void cuda_buffer_free(void *opaque, uint8_t *data)
     CHECK_CU(cu->cuCtxPopCurrent(&dummy));
 }
 
-static AVBufferRef *cuda_pool_alloc(void *opaque, buffer_size_t size)
+static AVBufferRef *cuda_pool_alloc(void *opaque, size_t size)
 {
     AVHWFramesContext        *ctx = opaque;
     AVHWDeviceContext *device_ctx = ctx->device_ctx;
diff --git a/libavutil/hwcontext_d3d11va.c b/libavutil/hwcontext_d3d11va.c
index 2a3549ebd8..27274ee3fa 100644
--- a/libavutil/hwcontext_d3d11va.c
+++ b/libavutil/hwcontext_d3d11va.c
@@ -202,7 +202,7 @@ static AVBufferRef *d3d11va_alloc_single(AVHWFramesContext *ctx)
     return wrap_texture_buf(tex, 0);
 }
 
-static AVBufferRef *d3d11va_pool_alloc(void *opaque, buffer_size_t size)
+static AVBufferRef *d3d11va_pool_alloc(void *opaque, size_t size)
 {
     AVHWFramesContext        *ctx = (AVHWFramesContext*)opaque;
     D3D11VAFramesContext       *s = ctx->internal->priv;
diff --git a/libavutil/hwcontext_dxva2.c b/libavutil/hwcontext_dxva2.c
index 33b3dc80ff..63b037da4a 100644
--- a/libavutil/hwcontext_dxva2.c
+++ b/libavutil/hwcontext_dxva2.c
@@ -124,7 +124,7 @@ static void dxva2_pool_release_dummy(void *opaque, uint8_t *data)
     // released in dxva2_frames_uninit()
 }
 
-static AVBufferRef *dxva2_pool_alloc(void *opaque, buffer_size_t size)
+static AVBufferRef *dxva2_pool_alloc(void *opaque, size_t size)
 {
     AVHWFramesContext      *ctx = (AVHWFramesContext*)opaque;
     DXVA2FramesContext       *s = ctx->internal->priv;
diff --git a/libavutil/hwcontext_opencl.c b/libavutil/hwcontext_opencl.c
index ee814602b2..41fac43229 100644
--- a/libavutil/hwcontext_opencl.c
+++ b/libavutil/hwcontext_opencl.c
@@ -1617,7 +1617,7 @@ static void opencl_pool_free(void *opaque, uint8_t *data)
     av_free(desc);
 }
 
-static AVBufferRef *opencl_pool_alloc(void *opaque, buffer_size_t size)
+static AVBufferRef *opencl_pool_alloc(void *opaque, size_t size)
 {
     AVHWFramesContext      *hwfc = opaque;
     AVOpenCLDeviceContext *hwctx = hwfc->device_ctx->hwctx;
diff --git a/libavutil/hwcontext_qsv.c b/libavutil/hwcontext_qsv.c
index 30b0d81f84..08a6e0ee1c 100644
--- a/libavutil/hwcontext_qsv.c
+++ b/libavutil/hwcontext_qsv.c
@@ -194,7 +194,7 @@ static void qsv_pool_release_dummy(void *opaque, uint8_t *data)
 {
 }
 
-static AVBufferRef *qsv_pool_alloc(void *opaque, buffer_size_t size)
+static AVBufferRef *qsv_pool_alloc(void *opaque, size_t size)
 {
     AVHWFramesContext    *ctx = (AVHWFramesContext*)opaque;
     QSVFramesContext       *s = ctx->internal->priv;
diff --git a/libavutil/hwcontext_vaapi.c b/libavutil/hwcontext_vaapi.c
index 4b81bd1f67..83e542876d 100644
--- a/libavutil/hwcontext_vaapi.c
+++ b/libavutil/hwcontext_vaapi.c
@@ -464,7 +464,7 @@ static void vaapi_buffer_free(void *opaque, uint8_t *data)
     }
 }
 
-static AVBufferRef *vaapi_pool_alloc(void *opaque, buffer_size_t size)
+static AVBufferRef *vaapi_pool_alloc(void *opaque, size_t size)
 {
     AVHWFramesContext     *hwfc = opaque;
     VAAPIFramesContext     *ctx = hwfc->internal->priv;
diff --git a/libavutil/hwcontext_vdpau.c b/libavutil/hwcontext_vdpau.c
index a6fd7126f3..5b78e95529 100644
--- a/libavutil/hwcontext_vdpau.c
+++ b/libavutil/hwcontext_vdpau.c
@@ -225,7 +225,7 @@ static void vdpau_buffer_free(void *opaque, uint8_t *data)
     device_priv->surf_destroy(surf);
 }
 
-static AVBufferRef *vdpau_pool_alloc(void *opaque, buffer_size_t size)
+static AVBufferRef *vdpau_pool_alloc(void *opaque, size_t size)
 {
     AVHWFramesContext             *ctx = opaque;
     VDPAUFramesContext           *priv = ctx->internal->priv;
diff --git a/libavutil/hwcontext_vulkan.c b/libavutil/hwcontext_vulkan.c
index 2e3faaaa1a..48327ad98f 100644
--- a/libavutil/hwcontext_vulkan.c
+++ b/libavutil/hwcontext_vulkan.c
@@ -1693,7 +1693,7 @@ static void try_export_flags(AVHWFramesContext *hwfc,
     }
 }
 
-static AVBufferRef *vulkan_pool_alloc(void *opaque, buffer_size_t size)
+static AVBufferRef *vulkan_pool_alloc(void *opaque, size_t size)
 {
     int err;
     AVVkFrame *f;
diff --git a/libavutil/internal.h b/libavutil/internal.h
index 854e9cbed2..7cd36ff742 100644
--- a/libavutil/internal.h
+++ b/libavutil/internal.h
@@ -292,11 +292,4 @@ void ff_check_pixfmt_descriptors(void);
  */
 int avpriv_dict_set_timestamp(AVDictionary **dict, const char *key, int64_t timestamp);
 
-// Temporary typedef to simplify porting all AVBufferRef users to size_t
-#if FF_API_BUFFER_SIZE_T
-typedef int buffer_size_t;
-#else
-typedef size_t buffer_size_t;
-#endif
-
 #endif /* AVUTIL_INTERNAL_H */
diff --git a/libavutil/version.h b/libavutil/version.h
index 0d015335c3..310145e350 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -108,9 +108,6 @@
 #ifndef FF_API_CHILD_CLASS_NEXT
 #define FF_API_CHILD_CLASS_NEXT         (LIBAVUTIL_VERSION_MAJOR < 57)
 #endif
-#ifndef FF_API_BUFFER_SIZE_T
-#define FF_API_BUFFER_SIZE_T            (LIBAVUTIL_VERSION_MAJOR < 57)
-#endif
 #ifndef FF_API_CPU_FLAGS
 #define FF_API_CPU_FLAGS                (LIBAVUTIL_VERSION_MAJOR < 57)
 #endif
diff --git a/libavutil/video_enc_params.c b/libavutil/video_enc_params.c
index 635176ab91..b9cdafddbb 100644
--- a/libavutil/video_enc_params.c
+++ b/libavutil/video_enc_params.c
@@ -63,10 +63,6 @@ av_video_enc_params_create_side_data(AVFrame *frame, enum AVVideoEncParamsType t
     par = av_video_enc_params_alloc(type, nb_blocks, &size);
     if (!par)
         return NULL;
-    if (size > INT_MAX) {
-        av_free(par);
-        return NULL;
-    }
     buf = av_buffer_create((uint8_t *)par, size, NULL, NULL, 0);
     if (!buf) {
         av_freep(&par);
