diff --git a/libavformat/Makefile b/libavformat/Makefile
index 0658fa3710..bb09dc6563 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -93,7 +93,7 @@ OBJS-$(CONFIG_AMRWB_DEMUXER)             += amr.o
 OBJS-$(CONFIG_ANM_DEMUXER)               += anm.o
 OBJS-$(CONFIG_APC_DEMUXER)               += apc.o
 OBJS-$(CONFIG_APE_DEMUXER)               += ape.o apetag.o img2.o
-OBJS-$(CONFIG_APM_DEMUXER)               += apm.o riffdec.o
+OBJS-$(CONFIG_APM_DEMUXER)               += apm.o
 OBJS-$(CONFIG_APNG_DEMUXER)              += apngdec.o
 OBJS-$(CONFIG_APNG_MUXER)                += apngenc.o
 OBJS-$(CONFIG_APTX_DEMUXER)              += aptxdec.o rawdec.o
diff --git a/libavformat/apm.c b/libavformat/apm.c
index dc59c16562..57d23200b0 100644
--- a/libavformat/apm.c
+++ b/libavformat/apm.c
@@ -21,12 +21,13 @@
  */
 #include "avformat.h"
 #include "internal.h"
-#include "riff.h"
 #include "libavutil/internal.h"
 #include "libavutil/intreadwrite.h"
 
-#define APM_FILE_HEADER_SIZE    20
-#define APM_VS12_CHUNK_SIZE     76
+#define APM_FILE_HEADER_SIZE    18
+#define APM_FILE_EXTRADATA_SIZE 80
+#define APM_EXTRADATA_SIZE      28
+
 #define APM_MAX_READ_SIZE       4096
 
 #define APM_TAG_CODEC           0x2000
@@ -43,34 +44,37 @@ typedef struct APMState {
     int32_t     saved_l;
 } APMState;
 
-typedef struct APMVS12Chunk {
+typedef struct APMExtraData {
     uint32_t    magic;
     uint32_t    file_size;
     uint32_t    data_size;
     uint32_t    unk1;
     uint32_t    unk2;
     APMState    state;
-    uint32_t    pad[7];
-} APMVS12Chunk;
+    uint32_t    unk3[7];
+    uint32_t    data;
+} APMExtraData;
 
-static void apm_parse_vs12(APMVS12Chunk *vs12, const uint8_t *buf)
+static void apm_parse_extradata(APMExtraData *ed, const uint8_t *buf)
 {
-    vs12->magic                 = AV_RL32(buf + 0);
-    vs12->file_size             = AV_RL32(buf + 4);
-    vs12->data_size             = AV_RL32(buf + 8);
-    vs12->unk1                  = AV_RL32(buf + 12);
-    vs12->unk2                  = AV_RL32(buf + 16);
-
-    vs12->state.has_saved       = AV_RL32(buf + 20);
-    vs12->state.predictor_r     = AV_RL32(buf + 24);
-    vs12->state.step_index_r    = AV_RL32(buf + 28);
-    vs12->state.saved_r         = AV_RL32(buf + 32);
-    vs12->state.predictor_l     = AV_RL32(buf + 36);
-    vs12->state.step_index_l    = AV_RL32(buf + 40);
-    vs12->state.saved_l         = AV_RL32(buf + 44);
-
-    for (int i = 0; i < FF_ARRAY_ELEMS(vs12->pad); i++)
-        vs12->pad[i]            = AV_RL32(buf + 48 + (i * 4));
+    ed->magic                 = AV_RL32(buf + 0);
+    ed->file_size             = AV_RL32(buf + 4);
+    ed->data_size             = AV_RL32(buf + 8);
+    ed->unk1                  = AV_RL32(buf + 12);
+    ed->unk2                  = AV_RL32(buf + 16);
+
+    ed->state.has_saved       = AV_RL32(buf + 20);
+    ed->state.predictor_r     = AV_RL32(buf + 24);
+    ed->state.step_index_r    = AV_RL32(buf + 28);
+    ed->state.saved_r         = AV_RL32(buf + 32);
+    ed->state.predictor_l     = AV_RL32(buf + 36);
+    ed->state.step_index_l    = AV_RL32(buf + 40);
+    ed->state.saved_l         = AV_RL32(buf + 44);
+
+    for (int i = 0; i < FF_ARRAY_ELEMS(ed->unk3); i++)
+        ed->unk3[i]           = AV_RL32(buf + 48 + (i * 4));
+
+    ed->data                  = AV_RL32(buf + 76);
 }
 
 static int apm_probe(const AVProbeData *p)
@@ -94,71 +98,75 @@ static int apm_read_header(AVFormatContext *s)
 {
     int64_t ret;
     AVStream *st;
-    APMVS12Chunk vs12;
-    uint8_t buf[APM_VS12_CHUNK_SIZE];
+    APMExtraData extradata;
+    AVCodecParameters *par;
+    uint8_t buf[APM_FILE_EXTRADATA_SIZE];
 
     if (!(st = avformat_new_stream(s, NULL)))
         return AVERROR(ENOMEM);
 
-    /* The header starts with a WAVEFORMATEX */
-    if ((ret = ff_get_wav_header(s, s->pb, st->codecpar, APM_FILE_HEADER_SIZE, 0)) < 0)
-        return ret;
-
-    if (st->codecpar->bits_per_coded_sample != 4)
+    /*
+     * This is 98% a WAVEFORMATEX, but there's something screwy with the extradata
+     * that ff_get_wav_header() can't (and shouldn't) handle properly.
+     */
+    if (avio_rl16(s->pb) != APM_TAG_CODEC)
         return AVERROR_INVALIDDATA;
 
-    if (st->codecpar->codec_tag != APM_TAG_CODEC)
+    par = st->codecpar;
+    par->channels              = avio_rl16(s->pb);
+    par->sample_rate           = avio_rl32(s->pb);
+    par->bit_rate              = avio_rl32(s->pb) * 8;
+    par->block_align           = avio_rl16(s->pb);
+    par->bits_per_coded_sample = avio_rl16(s->pb);
+
+    if (avio_rl16(s->pb) != APM_FILE_EXTRADATA_SIZE)
         return AVERROR_INVALIDDATA;
 
-    /* ff_get_wav_header() does most of the work, but we need to fix a few things. */
-    st->codecpar->codec_id              = AV_CODEC_ID_ADPCM_IMA_APM;
-    st->codecpar->codec_tag             = 0;
+    if (par->bits_per_coded_sample != 4)
+        return AVERROR_INVALIDDATA;
 
-    if (st->codecpar->channels == 2)
-        st->codecpar->channel_layout    = AV_CH_LAYOUT_STEREO;
-    else if (st->codecpar->channels == 1)
-        st->codecpar->channel_layout    = AV_CH_LAYOUT_MONO;
+    if (par->channels == 2)
+        par->channel_layout    = AV_CH_LAYOUT_STEREO;
+    else if (par->channels == 1)
+        par->channel_layout    = AV_CH_LAYOUT_MONO;
     else
         return AVERROR_INVALIDDATA;
 
-    st->codecpar->format                = AV_SAMPLE_FMT_S16;
-    st->codecpar->bits_per_raw_sample   = 16;
-    st->codecpar->bit_rate              = st->codecpar->channels *
-                                          st->codecpar->sample_rate *
-                                          st->codecpar->bits_per_coded_sample;
+    par->codec_type            = AVMEDIA_TYPE_AUDIO;
+    par->codec_id              = AV_CODEC_ID_ADPCM_IMA_APM;
+    par->format                = AV_SAMPLE_FMT_S16;
+    par->bits_per_raw_sample   = 16;
+
+    /* Now skip the pad that ruins everything. */
+    if ((ret = avio_skip(s->pb, 2)) < 0)
+        return ret;
 
-    if ((ret = avio_read(s->pb, buf, APM_VS12_CHUNK_SIZE)) < 0)
+    if ((ret = avio_read(s->pb, buf, APM_FILE_EXTRADATA_SIZE)) < 0)
         return ret;
-    else if (ret != APM_VS12_CHUNK_SIZE)
+    else if (ret != APM_FILE_EXTRADATA_SIZE)
         return AVERROR(EIO);
 
-    apm_parse_vs12(&vs12, buf);
+    apm_parse_extradata(&extradata, buf);
 
-    if (vs12.magic != APM_TAG_VS12) {
+    if (extradata.magic != APM_TAG_VS12 || extradata.data != APM_TAG_DATA)
         return AVERROR_INVALIDDATA;
-    }
 
-    if (vs12.state.has_saved) {
+    if (extradata.state.has_saved) {
         avpriv_request_sample(s, "Saved Samples");
         return AVERROR_PATCHWELCOME;
     }
 
-    if (avio_rl32(s->pb) != APM_TAG_DATA)
-        return AVERROR_INVALIDDATA;
-
-    if ((ret = ff_alloc_extradata(st->codecpar, 16)) < 0)
+    if ((ret = ff_alloc_extradata(par, APM_EXTRADATA_SIZE)) < 0)
         return ret;
 
-    AV_WL32(st->codecpar->extradata +  0, vs12.state.predictor_l);
-    AV_WL32(st->codecpar->extradata +  4, vs12.state.step_index_l);
-    AV_WL32(st->codecpar->extradata +  8, vs12.state.predictor_r);
-    AV_WL32(st->codecpar->extradata + 12, vs12.state.step_index_r);
+    /* Use the entire state as extradata. */
+    memcpy(par->extradata, buf + 20, APM_EXTRADATA_SIZE);
 
-    avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);
+    avpriv_set_pts_info(st, 64, 1, par->sample_rate);
     st->start_time  = 0;
-    st->duration    = vs12.data_size *
-                      (8 / st->codecpar->bits_per_coded_sample) /
-                      st->codecpar->channels;
+    st->duration    = extradata.data_size *
+                      (8 / par->bits_per_coded_sample) /
+                      par->channels;
     return 0;
 }
 
