diff mbox series

[FFmpeg-devel] avcodec: LEAD MCMP decoder

Message ID 1d90cbd18bffe5fc8d99ce361dec253c1728e19d.1668213509.git.pross@xvid.org
State New
Headers show
Series [FFmpeg-devel] avcodec: LEAD MCMP decoder | expand

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Commit Message

Peter Ross Nov. 12, 2022, 12:39 a.m. UTC
Partially fixes ticket #798
---

sample: https://trac.ffmpeg.org/raw-attachment/ticket/798/DaDa_CMP.avi

 configure                 |   1 +
 doc/general_contents.texi |   1 +
 libavcodec/Makefile       |   1 +
 libavcodec/allcodecs.c    |   1 +
 libavcodec/codec_desc.c   |   7 +
 libavcodec/codec_id.h     |   1 +
 libavcodec/leaddata.h     |  62 ++++++++
 libavcodec/leaddec.c      | 290 ++++++++++++++++++++++++++++++++++++++
 libavformat/riff.c        |   1 +
 9 files changed, 365 insertions(+)
 create mode 100644 libavcodec/leaddata.h
 create mode 100644 libavcodec/leaddec.c

Comments

James Almer Nov. 12, 2022, 3:33 p.m. UTC | #1
On 11/11/2022 9:39 PM, Peter Ross wrote:
> +static int lead_decode_frame(AVCodecContext *avctx, AVFrame * frame,
> +                             int * got_frame, AVPacket * avpkt)
> +{
> +    LeadContext *s = avctx->priv_data;
> +    const uint8_t * buf = avpkt->data;
> +    int ret, format, yuv20p_half = 0, fields = 1, q, size;
> +    GetBitContext gb;
> +    int16_t dc_pred[3] = {0, 0, 0};
> +    uint16_t dequant[2][64];
> +
> +    if (avpkt->size < 8)
> +        return AVERROR_INVALIDDATA;
> +
> +    format = AV_RL16(buf + 4);
> +    switch(format) {
> +    case 0x1000:
> +        avctx->pix_fmt = AV_PIX_FMT_YUV420P;
> +        break;
> +    case 0x2000:
> +        avctx->pix_fmt = AV_PIX_FMT_YUV444P;
> +        break;
> +    case 0x2006:
> +        avctx->pix_fmt = AV_PIX_FMT_YUV444P;
> +        fields = 2;
> +        break;
> +    case 0x8000:
> +        avctx->pix_fmt = AV_PIX_FMT_YUV420P;
> +        yuv20p_half = 1;

nit: maybe do

switch(format) {
case 0x8000:
     yuv20p_half = 1;
     // fall-through
case 0x1000:
     avctx->pix_fmt = AV_PIX_FMT_YUV420P;
     break;

> +        break;
> +    default:
> +        avpriv_request_sample(avctx, "unsupported format 0x%x", format);
> +        return AVERROR_PATCHWELCOME;
> +    }
> +
> +    q = AV_RL16(buf + 6);
> +    calc_dequant(dequant[0], ff_mjpeg_std_luminance_quant_tbl, q);
> +    calc_dequant(dequant[1], ff_mjpeg_std_chrominance_quant_tbl, q);
> +
> +    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
> +        return ret;
> +
> +    frame->key_frame = 1;
> +    frame->pict_type = AV_PICTURE_TYPE_I;

Shouldn't the codec have the prop AV_CODEC_PROP_INTRA_ONLY then? Or do 
some formats not yet supported have inter frames?

[...]

> +    if (yuv20p_half) {
> +        for (int mb_y = 0; mb_y < avctx->height / 16; mb_y++)
> +            for (int mb_x = 0; mb_x < avctx->width / 16; mb_x++)
> +                for (int b = 0; b < 4; b++) {
> +                    const VLCElem * dc_vlc = b < 2 ? luma_dc_vlc.table : chroma_dc_vlc.table;
> +                    int dc_bits            = b < 2 ? LUMA_DC_BITS : CHROMA_DC_BITS;
> +                    const VLCElem * ac_vlc = b < 2 ? luma_ac_vlc.table : chroma_ac_vlc.table;
> +                    int ac_bits            = b < 2 ? LUMA_AC_BITS : CHROMA_AC_BITS;
> +                    int plane              = b < 2 ? 0 : b - 1;
> +                    int x, y;
> +
> +                    if (b < 2) {
> +                        y = 16*mb_y + 8*(b >> 1);
> +                        x = 16*mb_x + 8*(b & 1);
> +                    } else {
> +                        y = 8*mb_y;
> +                        x = 8*mb_x;
> +                    }
> +
> +                    ret = decode_block(s, &gb, dc_vlc, dc_bits, ac_vlc, ac_bits,
> +                        dc_pred + plane, dequant[!(b < 4)],
> +                        frame->data[plane] + y*frame->linesize[plane] + x,
> +                        (b < 2 ? 2 : 1) * frame->linesize[plane]);
> +                    if (ret < 0)
> +                        return ret;
> +
> +                    if (b < 2)
> +                        copy_block8(frame->data[plane] + (y + 1)*frame->linesize[plane] + x,
> +                                    frame->data[plane] + y*frame->linesize[plane] + x,
> +                                    2*frame->linesize[plane], 2*frame->linesize[plane], 8);
> +                }
> +    } else if (avctx->pix_fmt == AV_PIX_FMT_YUV420P) {
> +        for (int mb_y = 0; mb_y < avctx->height / 16; mb_y++)
> +            for (int mb_x = 0; mb_x < avctx->width / 16; mb_x++)
> +                for (int b = 0; b < 6; b++) {
> +                    const VLCElem * dc_vlc = b < 4 ? luma_dc_vlc.table : chroma_dc_vlc.table;
> +                    int dc_bits            = b < 4 ? LUMA_DC_BITS : CHROMA_DC_BITS;
> +                    const VLCElem * ac_vlc = b < 4 ? luma_ac_vlc.table : chroma_ac_vlc.table;
> +                    int ac_bits            = b < 4 ? LUMA_AC_BITS : CHROMA_AC_BITS;
> +                    int plane              = b < 4 ? 0 : b - 3;
> +                    int x, y;
> +
> +                    if (b < 4) {
> +                        y = 16*mb_y + 8*(b>>1);
> +                        x = 16*mb_x + 8*(b&1);
> +                    } else {
> +                        y = 8*mb_y;
> +                        x = 8*mb_x;
> +                    }
> +
> +                    ret = decode_block(s, &gb, dc_vlc, dc_bits, ac_vlc, ac_bits,
> +                        dc_pred + plane, dequant[!(b < 4)],
> +                        frame->data[plane] + y*frame->linesize[plane] + x,
> +                        frame->linesize[plane]);
> +                    if (ret < 0)
> +                        return ret;
> +                }

You should be able to combine these two blocks, doing things like b < (4 
 >> yuv20p_half), b - (3 >> yuv20p_half) and such.
Michael Niedermayer Nov. 12, 2022, 4:42 p.m. UTC | #2
On Sat, Nov 12, 2022 at 11:39:19AM +1100, Peter Ross wrote:
> Partially fixes ticket #798
> ---
> 
> sample: https://trac.ffmpeg.org/raw-attachment/ticket/798/DaDa_CMP.avi
[...]

> +static av_cold int lead_decode_init(AVCodecContext * avctx)
> +{
> +    static AVOnce init_static_once = AV_ONCE_INIT;
> +    LeadContext *s = avctx->priv_data;
> +
> +    if (avctx->extradata_size < 20)
> +        return AVERROR_INVALIDDATA;
> +
> +    ff_idctdsp_init(&s->idsp, avctx);
> +    ff_permute_scantable(s->permutated_scantable, ff_zigzag_direct, s->idsp.idct_permutation);
> +
> +    ff_thread_once(&init_static_once, lead_init_static_data);
> +
> +    return 0;
> +}
> +
> +static void calc_dequant(uint16_t * dequant, const uint8_t * quant_tbl, int q)
> +{
> +    for (int i = 0; i < 64; i++)
> +        dequant[i] = av_clip(q * quant_tbl[ff_zigzag_direct[i]] / 50, 2, 32767);
> +}
> +

> +static int decode_block(LeadContext * s, GetBitContext * gb,
> +                        const VLCElem * dc_table, int dc_bits, const VLCElem * ac_table, int ac_bits,
> +                        int16_t * dc_pred, const uint16_t * dequant,
> +                        uint8_t * dst, int stride)
> +{
> +    int16_t block[64];
> +    int size;
> +

> +    memset(block, 0, sizeof(block));

clear_block()


> +
> +    size = get_vlc2(gb, dc_table, dc_bits, 1);
> +    if (size < 0)
> +        return AVERROR_INVALIDDATA;
> +
> +    if (size)
> +        *dc_pred += get_xbits(gb, size);
> +
> +    block[0] = (1 << 10) + *dc_pred * dequant[0];
> +
> +    for (int i = 1; i < 64; i++) {

> +        int symbol = get_vlc2(gb, ac_table, ac_bits, 2);
> +        if (size < 0)

i think you want to check symbol here
also if you want you could probably map the unused vlcs to things causing  the i>=64 check to fail later
to avoid a 2nd check but its probably not worth the work for this codec


> +            return AVERROR_INVALIDDATA;
> +
> +        if (!symbol)
> +            break;
> +
> +        i += symbol >> 4;
> +        if (i >= 64)
> +            return AVERROR_INVALIDDATA;
> +
> +        size = symbol & 0xF;
> +        if (size)
> +            block[s->permutated_scantable[i]] = get_xbits(gb, size) * dequant[i];
> +    }
> +
> +    s->idsp.idct_put(dst, stride, block);

    void (*idct_put)(uint8_t *dest /* align 8 */,
                     ptrdiff_t line_size, int16_t *block /* align 16 */);
block needs to be aligned to 16 bytes

[...]

thx
diff mbox series

Patch

diff --git a/configure b/configure
index e6470dc03b..56af100e94 100755
--- a/configure
+++ b/configure
@@ -2861,6 +2861,7 @@  ipu_decoder_select="mpegvideodec"
 jpegls_decoder_select="mjpeg_decoder"
 jv_decoder_select="blockdsp"
 lagarith_decoder_select="llviddsp"
+lead_decoder_select="idctdsp jpegtables"
 ljpeg_encoder_select="jpegtables"
 lscr_decoder_select="inflate_wrapper"
 magicyuv_decoder_select="llviddsp"
diff --git a/doc/general_contents.texi b/doc/general_contents.texi
index 8399fcb6b7..6832055316 100644
--- a/doc/general_contents.texi
+++ b/doc/general_contents.texi
@@ -987,6 +987,7 @@  following image formats are supported:
 @item Lagarith               @tab     @tab  X
 @item LCL (LossLess Codec Library) MSZH  @tab     @tab  X
 @item LCL (LossLess Codec Library) ZLIB  @tab  E  @tab  E
+@item LEAD MCMP              @tab     @tab  X
 @item LOCO                   @tab     @tab  X
 @item LucasArts SANM/Smush   @tab     @tab  X
     @tab Used in LucasArts games / SMUSH animations.
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 94dc75a1b2..aa99eba7b7 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -463,6 +463,7 @@  OBJS-$(CONFIG_JV_DECODER)              += jvdec.o
 OBJS-$(CONFIG_KGV1_DECODER)            += kgv1dec.o
 OBJS-$(CONFIG_KMVC_DECODER)            += kmvc.o
 OBJS-$(CONFIG_LAGARITH_DECODER)        += lagarith.o lagarithrac.o
+OBJS-$(CONFIG_LEAD_DECODER)            += leaddec.o jpegquanttables.o
 OBJS-$(CONFIG_LJPEG_ENCODER)           += ljpegenc.o mjpegenc_common.o
 OBJS-$(CONFIG_LOCO_DECODER)            += loco.o
 OBJS-$(CONFIG_LSCR_DECODER)            += lscrdec.o png.o pngdec.o pngdsp.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index f5ec3bc6e1..4b96443946 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -187,6 +187,7 @@  extern const FFCodec ff_jv_decoder;
 extern const FFCodec ff_kgv1_decoder;
 extern const FFCodec ff_kmvc_decoder;
 extern const FFCodec ff_lagarith_decoder;
+extern const FFCodec ff_lead_decoder;
 extern const FFCodec ff_ljpeg_encoder;
 extern const FFCodec ff_loco_decoder;
 extern const FFCodec ff_lscr_decoder;
diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
index 24a0433dba..9a1720f615 100644
--- a/libavcodec/codec_desc.c
+++ b/libavcodec/codec_desc.c
@@ -1923,6 +1923,13 @@  static const AVCodecDescriptor codec_descriptors[] = {
         .long_name = NULL_IF_CONFIG_SMALL("ViewQuest VQC"),
         .props     = AV_CODEC_PROP_LOSSY,
     },
+    {
+        .id        = AV_CODEC_ID_LEAD,
+        .type      = AVMEDIA_TYPE_VIDEO,
+        .name      = "lead",
+        .long_name = NULL_IF_CONFIG_SMALL("LEAD MCMP"),
+        .props     = AV_CODEC_PROP_LOSSY,
+    },
 
     /* various PCM "codecs" */
     {
diff --git a/libavcodec/codec_id.h b/libavcodec/codec_id.h
index f436a2b624..31c590278e 100644
--- a/libavcodec/codec_id.h
+++ b/libavcodec/codec_id.h
@@ -320,6 +320,7 @@  enum AVCodecID {
     AV_CODEC_ID_WBMP,
     AV_CODEC_ID_MEDIA100,
     AV_CODEC_ID_VQC,
+    AV_CODEC_ID_LEAD,
 
     /* various PCM "codecs" */
     AV_CODEC_ID_FIRST_AUDIO = 0x10000,     ///< A dummy id pointing at the start of audio codecs
diff --git a/libavcodec/leaddata.h b/libavcodec/leaddata.h
new file mode 100644
index 0000000000..525b582cf7
--- /dev/null
+++ b/libavcodec/leaddata.h
@@ -0,0 +1,62 @@ 
+/*
+ * LEAD MCMP decoder tables
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_LEADDATA_H
+#define AVCODEC_LEADDATA_H
+
+#include <stdint.h>
+
+static const uint8_t luma_dc_len[]={
+    2, 3, 3, 3, 3, 3, 4, 5, 6, 7, 8, 9
+};
+
+static const uint8_t chroma_dc_len[]={
+    2, 2, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
+};
+
+static const uint8_t luma_ac_len[]={
+    2, 2, 3, 4, 4, 4, 5, 5, 5, 6, 6, 7, 7, 7, 7, 8,
+    8, 8, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 11, 11, 11, 11,
+    12, 12, 12, 12, 15, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16
+};
+
+static const uint8_t chroma_ac_len[]={
+    2, 2, 3, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7,
+    8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10,
+    11, 11, 11, 11, 12, 12, 12, 12, 14, 15, 15, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
+    16, 16
+};
+
+#endif /* AVCODEC_LEADDATA_H */
diff --git a/libavcodec/leaddec.c b/libavcodec/leaddec.c
new file mode 100644
index 0000000000..3bda06458a
--- /dev/null
+++ b/libavcodec/leaddec.c
@@ -0,0 +1,290 @@ 
+/*
+ * LEAD MCMP decoder
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "avcodec.h"
+#include "codec_internal.h"
+#include "copy_block.h"
+#include "decode.h"
+#include "get_bits.h"
+#include "idctdsp.h"
+#include "jpegquanttables.h"
+#include "jpegtables.h"
+#include "leaddata.h"
+#include "libavutil/thread.h"
+
+#define LUMA_DC_BITS 9
+#define CHROMA_DC_BITS 11
+#define LUMA_AC_BITS 10
+#define CHROMA_AC_BITS 10
+
+static VLC luma_dc_vlc;
+static VLC chroma_dc_vlc;
+static VLC luma_ac_vlc;
+static VLC chroma_ac_vlc;
+
+static av_cold void lead_init_static_data(void)
+{
+    INIT_VLC_STATIC_FROM_LENGTHS(&luma_dc_vlc, LUMA_DC_BITS, FF_ARRAY_ELEMS(luma_dc_len),
+                                 luma_dc_len, 1,
+                                 0, 0, 0,
+                                 0, 0, 1 << LUMA_DC_BITS);
+    INIT_VLC_STATIC_FROM_LENGTHS(&chroma_dc_vlc, CHROMA_DC_BITS, FF_ARRAY_ELEMS(chroma_dc_len),
+                                 chroma_dc_len, 1,
+                                 0, 0, 0,
+                                 0, 0, 1 << CHROMA_DC_BITS);
+    INIT_VLC_STATIC_FROM_LENGTHS(&luma_ac_vlc, LUMA_AC_BITS, FF_ARRAY_ELEMS(luma_ac_len),
+                                 luma_ac_len, 1,
+                                 ff_mjpeg_val_ac_luminance, 1, 1,
+                                 0, 0, 1160);
+    INIT_VLC_STATIC_FROM_LENGTHS(&chroma_ac_vlc, CHROMA_AC_BITS, FF_ARRAY_ELEMS(chroma_ac_len),
+                                 chroma_ac_len, 1,
+                                 ff_mjpeg_val_ac_chrominance, 1, 1,
+                                 0, 0, 1160);
+}
+
+typedef struct LeadContext {
+    uint8_t *bitstream_buf;
+    unsigned int bitstream_buf_size;
+    IDCTDSPContext idsp;
+    uint8_t permutated_scantable[64];
+} LeadContext;
+
+static av_cold int lead_decode_init(AVCodecContext * avctx)
+{
+    static AVOnce init_static_once = AV_ONCE_INIT;
+    LeadContext *s = avctx->priv_data;
+
+    if (avctx->extradata_size < 20)
+        return AVERROR_INVALIDDATA;
+
+    ff_idctdsp_init(&s->idsp, avctx);
+    ff_permute_scantable(s->permutated_scantable, ff_zigzag_direct, s->idsp.idct_permutation);
+
+    ff_thread_once(&init_static_once, lead_init_static_data);
+
+    return 0;
+}
+
+static void calc_dequant(uint16_t * dequant, const uint8_t * quant_tbl, int q)
+{
+    for (int i = 0; i < 64; i++)
+        dequant[i] = av_clip(q * quant_tbl[ff_zigzag_direct[i]] / 50, 2, 32767);
+}
+
+static int decode_block(LeadContext * s, GetBitContext * gb,
+                        const VLCElem * dc_table, int dc_bits, const VLCElem * ac_table, int ac_bits,
+                        int16_t * dc_pred, const uint16_t * dequant,
+                        uint8_t * dst, int stride)
+{
+    int16_t block[64];
+    int size;
+
+    memset(block, 0, sizeof(block));
+
+    size = get_vlc2(gb, dc_table, dc_bits, 1);
+    if (size < 0)
+        return AVERROR_INVALIDDATA;
+
+    if (size)
+        *dc_pred += get_xbits(gb, size);
+
+    block[0] = (1 << 10) + *dc_pred * dequant[0];
+
+    for (int i = 1; i < 64; i++) {
+        int symbol = get_vlc2(gb, ac_table, ac_bits, 2);
+        if (size < 0)
+            return AVERROR_INVALIDDATA;
+
+        if (!symbol)
+            break;
+
+        i += symbol >> 4;
+        if (i >= 64)
+            return AVERROR_INVALIDDATA;
+
+        size = symbol & 0xF;
+        if (size)
+            block[s->permutated_scantable[i]] = get_xbits(gb, size) * dequant[i];
+    }
+
+    s->idsp.idct_put(dst, stride, block);
+    return 0;
+}
+
+static int lead_decode_frame(AVCodecContext *avctx, AVFrame * frame,
+                             int * got_frame, AVPacket * avpkt)
+{
+    LeadContext *s = avctx->priv_data;
+    const uint8_t * buf = avpkt->data;
+    int ret, format, yuv20p_half = 0, fields = 1, q, size;
+    GetBitContext gb;
+    int16_t dc_pred[3] = {0, 0, 0};
+    uint16_t dequant[2][64];
+
+    if (avpkt->size < 8)
+        return AVERROR_INVALIDDATA;
+
+    format = AV_RL16(buf + 4);
+    switch(format) {
+    case 0x1000:
+        avctx->pix_fmt = AV_PIX_FMT_YUV420P;
+        break;
+    case 0x2000:
+        avctx->pix_fmt = AV_PIX_FMT_YUV444P;
+        break;
+    case 0x2006:
+        avctx->pix_fmt = AV_PIX_FMT_YUV444P;
+        fields = 2;
+        break;
+    case 0x8000:
+        avctx->pix_fmt = AV_PIX_FMT_YUV420P;
+        yuv20p_half = 1;
+        break;
+    default:
+        avpriv_request_sample(avctx, "unsupported format 0x%x", format);
+        return AVERROR_PATCHWELCOME;
+    }
+
+    q = AV_RL16(buf + 6);
+    calc_dequant(dequant[0], ff_mjpeg_std_luminance_quant_tbl, q);
+    calc_dequant(dequant[1], ff_mjpeg_std_chrominance_quant_tbl, q);
+
+    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
+        return ret;
+
+    frame->key_frame = 1;
+    frame->pict_type = AV_PICTURE_TYPE_I;
+
+    av_fast_padded_malloc(&s->bitstream_buf, &s->bitstream_buf_size, avpkt->size - 8);
+    if (!s->bitstream_buf)
+        return AVERROR(ENOMEM);
+
+    size = 0;
+    for (int i = 8; i < avpkt->size; i++) {
+        int src = buf[i] ^ 0x80;
+        s->bitstream_buf[size++] = src;
+        if (src == 0xFF && i + 1 < avpkt->size && (buf[i + 1] ^ 0x80) == 0x00)
+            i++;
+    }
+
+    init_get_bits8(&gb, s->bitstream_buf, size);
+
+    if (yuv20p_half) {
+        for (int mb_y = 0; mb_y < avctx->height / 16; mb_y++)
+            for (int mb_x = 0; mb_x < avctx->width / 16; mb_x++)
+                for (int b = 0; b < 4; b++) {
+                    const VLCElem * dc_vlc = b < 2 ? luma_dc_vlc.table : chroma_dc_vlc.table;
+                    int dc_bits            = b < 2 ? LUMA_DC_BITS : CHROMA_DC_BITS;
+                    const VLCElem * ac_vlc = b < 2 ? luma_ac_vlc.table : chroma_ac_vlc.table;
+                    int ac_bits            = b < 2 ? LUMA_AC_BITS : CHROMA_AC_BITS;
+                    int plane              = b < 2 ? 0 : b - 1;
+                    int x, y;
+
+                    if (b < 2) {
+                        y = 16*mb_y + 8*(b >> 1);
+                        x = 16*mb_x + 8*(b & 1);
+                    } else {
+                        y = 8*mb_y;
+                        x = 8*mb_x;
+                    }
+
+                    ret = decode_block(s, &gb, dc_vlc, dc_bits, ac_vlc, ac_bits,
+                        dc_pred + plane, dequant[!(b < 4)],
+                        frame->data[plane] + y*frame->linesize[plane] + x,
+                        (b < 2 ? 2 : 1) * frame->linesize[plane]);
+                    if (ret < 0)
+                        return ret;
+
+                    if (b < 2)
+                        copy_block8(frame->data[plane] + (y + 1)*frame->linesize[plane] + x,
+                                    frame->data[plane] + y*frame->linesize[plane] + x,
+                                    2*frame->linesize[plane], 2*frame->linesize[plane], 8);
+                }
+    } else if (avctx->pix_fmt == AV_PIX_FMT_YUV420P) {
+        for (int mb_y = 0; mb_y < avctx->height / 16; mb_y++)
+            for (int mb_x = 0; mb_x < avctx->width / 16; mb_x++)
+                for (int b = 0; b < 6; b++) {
+                    const VLCElem * dc_vlc = b < 4 ? luma_dc_vlc.table : chroma_dc_vlc.table;
+                    int dc_bits            = b < 4 ? LUMA_DC_BITS : CHROMA_DC_BITS;
+                    const VLCElem * ac_vlc = b < 4 ? luma_ac_vlc.table : chroma_ac_vlc.table;
+                    int ac_bits            = b < 4 ? LUMA_AC_BITS : CHROMA_AC_BITS;
+                    int plane              = b < 4 ? 0 : b - 3;
+                    int x, y;
+
+                    if (b < 4) {
+                        y = 16*mb_y + 8*(b>>1);
+                        x = 16*mb_x + 8*(b&1);
+                    } else {
+                        y = 8*mb_y;
+                        x = 8*mb_x;
+                    }
+
+                    ret = decode_block(s, &gb, dc_vlc, dc_bits, ac_vlc, ac_bits,
+                        dc_pred + plane, dequant[!(b < 4)],
+                        frame->data[plane] + y*frame->linesize[plane] + x,
+                        frame->linesize[plane]);
+                    if (ret < 0)
+                        return ret;
+                }
+    } else {
+        for (int f = 0; f < fields; f++)
+            for (int j = 0; j < avctx->height / fields / 8; j++)
+                for (int i = 0; i < avctx->width / 8; i++)
+                    for (int plane = 0; plane < 3; plane++) {
+                        const VLCElem * dc_vlc = !plane ? luma_dc_vlc.table : chroma_dc_vlc.table;
+                        int dc_bits            = !plane ? LUMA_DC_BITS : CHROMA_DC_BITS;
+                        const VLCElem * ac_vlc = !plane ? luma_ac_vlc.table : chroma_ac_vlc.table;
+                        int ac_bits            = !plane ? LUMA_AC_BITS : CHROMA_AC_BITS;
+
+                        ret = decode_block(s, &gb, dc_vlc, dc_bits, ac_vlc, ac_bits,
+                            dc_pred + plane, dequant[!!plane],
+                            frame->data[plane] + (f + 8*j*fields)*frame->linesize[plane] + 8*i,
+                            fields * frame->linesize[plane]);
+                        if (ret < 0)
+                            return ret;
+                    }
+    }
+
+    *got_frame = 1;
+
+    return avpkt->size;
+}
+
+static av_cold int lead_decode_end(AVCodecContext * avctx)
+{
+    LeadContext *s = avctx->priv_data;
+
+    av_freep(&s->bitstream_buf);
+
+    return 0;
+}
+
+const FFCodec ff_lead_decoder = {
+    .p.name         = "lead",
+    CODEC_LONG_NAME("LEAD MCMP"),
+    .p.type         = AVMEDIA_TYPE_VIDEO,
+    .p.id           = AV_CODEC_ID_LEAD,
+    .priv_data_size = sizeof(LeadContext),
+    .init           = lead_decode_init,
+    .close          = lead_decode_end,
+    FF_CODEC_DECODE_CB(lead_decode_frame),
+    .p.capabilities = AV_CODEC_CAP_DR1,
+    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,
+};
diff --git a/libavformat/riff.c b/libavformat/riff.c
index 7319406b39..8401ae3668 100644
--- a/libavformat/riff.c
+++ b/libavformat/riff.c
@@ -501,6 +501,7 @@  const AVCodecTag ff_codec_bmp_tags[] = {
     { AV_CODEC_ID_NOTCHLC,      MKTAG('n', 'l', 'c', '1') },
     { AV_CODEC_ID_VQC,          MKTAG('V', 'Q', 'C', '1') },
     { AV_CODEC_ID_VQC,          MKTAG('V', 'Q', 'C', '2') },
+    { AV_CODEC_ID_LEAD,         MKTAG('L', 'E', 'A', 'D') },
     { AV_CODEC_ID_NONE,         0 }
 };