lavc: Add coded bitstream read/write support for MPEG-2

(cherry picked from commit 2bc9ba8d3c41f3a8e56484bd67b05040c7909a01)
(cherry picked from commit a41b69b5eb950c10d8ede472bcc4e88ce4246db9)

7 files changed, 1028 insertions, 0 deletions

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 39b7dd1e2f..0265c92130 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -62,6 +62,7 @@ OBJS-$(CONFIG_CABAC)                   += cabac.o
 OBJS-$(CONFIG_CBS)                     += cbs.o
 OBJS-$(CONFIG_CBS_H264)                += cbs_h2645.o h2645_parse.o
 OBJS-$(CONFIG_CBS_H265)                += cbs_h2645.o h2645_parse.o
+OBJS-$(CONFIG_CBS_MPEG2)               += cbs_mpeg2.o
 OBJS-$(CONFIG_CRYSTALHD)               += crystalhd.o
 OBJS-$(CONFIG_DCT)                     += dct.o dct32_fixed.o dct32_float.o
 OBJS-$(CONFIG_ERROR_RESILIENCE)        += error_resilience.o
diff --git a/libavcodec/cbs.c b/libavcodec/cbs.c
index d7eb3033c4..97ab520c22 100644
--- a/libavcodec/cbs.c
+++ b/libavcodec/cbs.c
@@ -34,6 +34,9 @@ static const CodedBitstreamType *cbs_type_table[] = {
 #if CONFIG_CBS_H265
     &ff_cbs_type_h265,
 #endif
+#if CONFIG_CBS_MPEG2
+    &ff_cbs_type_mpeg2,
+#endif
 };
 
 int ff_cbs_init(CodedBitstreamContext **ctx_ptr,
diff --git a/libavcodec/cbs.h b/libavcodec/cbs.h
index a367fd0bf6..ff97880610 100644
--- a/libavcodec/cbs.h
+++ b/libavcodec/cbs.h
@@ -45,6 +45,7 @@ struct CodedBitstreamType;
  *
  * H.264 / AVC: nal_unit_type
  * H.265 / HEVC: nal_unit_type
+ * MPEG-2: start code value (without prefix)
  */
 typedef uint32_t CodedBitstreamUnitType;
 
diff --git a/libavcodec/cbs_internal.h b/libavcodec/cbs_internal.h
index f8263bef0a..ae0b417b43 100644
--- a/libavcodec/cbs_internal.h
+++ b/libavcodec/cbs_internal.h
@@ -85,6 +85,7 @@ int ff_cbs_write_unsigned(CodedBitstreamContext *ctx, PutBitContext *pbc,
 
 extern const CodedBitstreamType ff_cbs_type_h264;
 extern const CodedBitstreamType ff_cbs_type_h265;
+extern const CodedBitstreamType ff_cbs_type_mpeg2;
 
 
 #endif /* AVCODEC_CBS_INTERNAL_H */
diff --git a/libavcodec/cbs_mpeg2.c b/libavcodec/cbs_mpeg2.c
new file mode 100644
index 0000000000..d137762227
--- /dev/null
+++ b/libavcodec/cbs_mpeg2.c
@@ -0,0 +1,414 @@
+/*
+ * 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 "libavutil/avassert.h"
+
+#include "cbs.h"
+#include "cbs_internal.h"
+#include "cbs_mpeg2.h"
+#include "internal.h"
+
+
+#define HEADER(name) do { \
+        ff_cbs_trace_header(ctx, name); \
+    } while (0)
+
+#define CHECK(call) do { \
+        err = (call); \
+        if (err < 0) \
+            return err; \
+    } while (0)
+
+#define FUNC_NAME(rw, codec, name) cbs_ ## codec ## _ ## rw ## _ ## name
+#define FUNC_MPEG2(rw, name) FUNC_NAME(rw, mpeg2, name)
+#define FUNC(name) FUNC_MPEG2(READWRITE, name)
+
+
+#define READ
+#define READWRITE read
+#define RWContext GetBitContext
+
+#define xui(width, name, var) do { \
+        uint32_t value = 0; \
+        CHECK(ff_cbs_read_unsigned(ctx, rw, width, #name, \
+                                   &value, 0, (1 << width) - 1)); \
+        var = value; \
+    } while (0)
+
+#define ui(width, name) \
+        xui(width, name, current->name)
+
+#define marker_bit() do { \
+        av_unused int one = 1; \
+        CHECK(ff_cbs_read_unsigned(ctx, rw, 1, "marker_bit", &one, 1, 1)); \
+    } while (0)
+
+#define nextbits(width, compare, var) \
+    (get_bits_left(rw) >= width && \
+     (var = show_bits(rw, width)) == (compare))
+
+#include "cbs_mpeg2_syntax_template.c"
+
+#undef READ
+#undef READWRITE
+#undef RWContext
+#undef xui
+#undef ui
+#undef marker_bit
+#undef nextbits
+
+
+#define WRITE
+#define READWRITE write
+#define RWContext PutBitContext
+
+#define xui(width, name, var) do { \
+        CHECK(ff_cbs_write_unsigned(ctx, rw, width, #name, \
+                                    var, 0, (1 << width) - 1)); \
+    } while (0)
+
+#define ui(width, name) \
+        xui(width, name, current->name)
+
+#define marker_bit() do { \
+        CHECK(ff_cbs_write_unsigned(ctx, rw, 1, "marker_bit", 1, 1, 1)); \
+    } while (0)
+
+#define nextbits(width, compare, var) (var)
+
+#include "cbs_mpeg2_syntax_template.c"
+
+#undef READ
+#undef READWRITE
+#undef RWContext
+#undef xui
+#undef ui
+#undef marker_bit
+#undef nextbits
+
+
+static int cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx,
+                                    CodedBitstreamFragment *frag,
+                                    int header)
+{
+    const uint8_t *start, *end;
+    uint8_t *unit_data;
+    uint32_t start_code = -1, next_start_code = -1;
+    size_t unit_size;
+    int err, i, unit_type;
+
+    start = avpriv_find_start_code(frag->data, frag->data + frag->data_size,
+                                   &start_code);
+    for (i = 0;; i++) {
+        end = avpriv_find_start_code(start, frag->data + frag->data_size,
+                                     &next_start_code);
+
+        unit_type = start_code & 0xff;
+
+        // The start and end pointers point at to the byte following the
+        // start_code_identifier in the start code that they found.
+        if (end == frag->data + frag->data_size) {
+            // We didn't find a start code, so this is the final unit.
+            unit_size = end - (start - 1);
+        } else {
+            // Unit runs from start to the beginning of the start code
+            // pointed to by end (including any padding zeroes).
+            unit_size = (end - 4) - (start - 1);
+        }
+
+        unit_data = av_malloc(unit_size + AV_INPUT_BUFFER_PADDING_SIZE);
+        if (!unit_data)
+            return AVERROR(ENOMEM);
+        memcpy(unit_data, start - 1, unit_size);
+        memset(unit_data + unit_size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
+
+        err = ff_cbs_insert_unit_data(ctx, frag, i, unit_type,
+                                      unit_data, unit_size);
+        if (err < 0) {
+            av_freep(&unit_data);
+            return err;
+        }
+
+        if (end == frag->data + frag->data_size)
+            break;
+
+        start_code = next_start_code;
+        start = end;
+    }
+
+    return 0;
+}
+
+static int cbs_mpeg2_read_unit(CodedBitstreamContext *ctx,
+                               CodedBitstreamUnit *unit)
+{
+    GetBitContext gbc;
+    int err;
+
+    err = init_get_bits(&gbc, unit->data, 8 * unit->data_size);
+    if (err < 0)
+        return err;
+
+    if (MPEG2_START_IS_SLICE(unit->type)) {
+        MPEG2RawSlice *slice;
+        int pos, len;
+
+        slice = av_mallocz(sizeof(*slice));
+        if (!slice)
+            return AVERROR(ENOMEM);
+        err = cbs_mpeg2_read_slice_header(ctx, &gbc, &slice->header);
+        if (err < 0) {
+            av_free(slice);
+            return err;
+        }
+
+        pos = get_bits_count(&gbc);
+        len = unit->data_size;
+
+        slice->data_size = len - pos / 8;
+        slice->data = av_malloc(slice->data_size +
+                                AV_INPUT_BUFFER_PADDING_SIZE);
+        if (!slice->data) {
+            av_free(slice);
+            return AVERROR(ENOMEM);
+        }
+
+        memcpy(slice->data,
+               unit->data + pos / 8, slice->data_size);
+        memset(slice->data + slice->data_size, 0,
+               AV_INPUT_BUFFER_PADDING_SIZE);
+        slice->data_bit_start = pos % 8;
+
+        unit->content = slice;
+
+    } else {
+        switch (unit->type) {
+#define START(start_code, type, func) \
+        case start_code: \
+            { \
+                type *header; \
+                header = av_mallocz(sizeof(*header)); \
+                if (!header) \
+                    return AVERROR(ENOMEM); \
+                err = cbs_mpeg2_read_ ## func(ctx, &gbc, header); \
+                if (err < 0) { \
+                    av_free(header); \
+                    return err; \
+                } \
+                unit->content = header; \
+            } \
+            break;
+            START(0x00, MPEG2RawPictureHeader,  picture_header);
+            START(0xb2, MPEG2RawUserData,       user_data);
+            START(0xb3, MPEG2RawSequenceHeader, sequence_header);
+            START(0xb5, MPEG2RawExtensionData,  extension_data);
+            START(0xb8, MPEG2RawGroupOfPicturesHeader, group_of_pictures_header);
+#undef START
+        default:
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Unknown start code %02x.\n",
+                   unit->type);
+            return AVERROR_INVALIDDATA;
+        }
+    }
+
+    return 0;
+}
+
+static int cbs_mpeg2_write_header(CodedBitstreamContext *ctx,
+                                  CodedBitstreamUnit *unit,
+                                  PutBitContext *pbc)
+{
+    int err;
+
+    switch (unit->type) {
+#define START(start_code, type, func) \
+    case start_code: \
+        err = cbs_mpeg2_write_ ## func(ctx, pbc, unit->content); \
+        break;
+        START(0x00, MPEG2RawPictureHeader,  picture_header);
+        START(0xb2, MPEG2RawUserData,       user_data);
+        START(0xb3, MPEG2RawSequenceHeader, sequence_header);
+        START(0xb5, MPEG2RawExtensionData,  extension_data);
+        START(0xb8, MPEG2RawGroupOfPicturesHeader, group_of_pictures_header);
+#undef START
+    default:
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Write unimplemented for start "
+               "code %02"PRIu32".\n", unit->type);
+        return AVERROR_PATCHWELCOME;
+    }
+
+    return err;
+}
+
+static int cbs_mpeg2_write_slice(CodedBitstreamContext *ctx,
+                                 CodedBitstreamUnit *unit,
+                                 PutBitContext *pbc)
+{
+    MPEG2RawSlice *slice = unit->content;
+    GetBitContext gbc;
+    size_t bits_left;
+    int err;
+
+    err = cbs_mpeg2_write_slice_header(ctx, pbc, &slice->header);
+    if (err < 0)
+        return err;
+
+    if (slice->data) {
+        if (slice->data_size * 8 + 8 > put_bits_left(pbc))
+            return AVERROR(ENOSPC);
+
+        init_get_bits(&gbc, slice->data, slice->data_size * 8);
+        skip_bits_long(&gbc, slice->data_bit_start);
+
+        while (get_bits_left(&gbc) > 15)
+            put_bits(pbc, 16, get_bits(&gbc, 16));
+
+        bits_left = get_bits_left(&gbc);
+        put_bits(pbc, bits_left, get_bits(&gbc, bits_left));
+
+        // Align with zeroes.
+        while (put_bits_count(pbc) % 8 != 0)
+            put_bits(pbc, 1, 0);
+    }
+
+    return 0;
+}
+
+static int cbs_mpeg2_write_unit(CodedBitstreamContext *ctx,
+                                CodedBitstreamUnit *unit)
+{
+    CodedBitstreamMPEG2Context *priv = ctx->priv_data;
+    PutBitContext pbc;
+    int err;
+
+    if (!priv->write_buffer) {
+        // Initial write buffer size is 1MB.
+        priv->write_buffer_size = 1024 * 1024;
+
+    reallocate_and_try_again:
+        err = av_reallocp(&priv->write_buffer, priv->write_buffer_size);
+        if (err < 0) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Unable to allocate a "
+                   "sufficiently large write buffer (last attempt "
+                   "%zu bytes).\n", priv->write_buffer_size);
+            return err;
+        }
+    }
+
+    init_put_bits(&pbc, priv->write_buffer, priv->write_buffer_size);
+
+    if (unit->type >= 0x01 && unit->type <= 0xaf)
+        err = cbs_mpeg2_write_slice(ctx, unit, &pbc);
+    else
+        err = cbs_mpeg2_write_header(ctx, unit, &pbc);
+
+    if (err == AVERROR(ENOSPC)) {
+        // Overflow.
+        priv->write_buffer_size *= 2;
+        goto reallocate_and_try_again;
+    }
+    if (err < 0) {
+        // Write failed for some other reason.
+        return err;
+    }
+
+    if (put_bits_count(&pbc) % 8)
+        unit->data_bit_padding = 8 - put_bits_count(&pbc) % 8;
+    else
+        unit->data_bit_padding = 0;
+
+    unit->data_size = (put_bits_count(&pbc) + 7) / 8;
+    flush_put_bits(&pbc);
+
+    err = av_reallocp(&unit->data, unit->data_size);
+    if (err < 0)
+        return err;
+
+    memcpy(unit->data, priv->write_buffer, unit->data_size);
+
+    return 0;
+}
+
+static int cbs_mpeg2_assemble_fragment(CodedBitstreamContext *ctx,
+                                       CodedBitstreamFragment *frag)
+{
+    uint8_t *data;
+    size_t size, dp, sp;
+    int i;
+
+    size = 0;
+    for (i = 0; i < frag->nb_units; i++)
+        size += 3 + frag->units[i].data_size;
+
+    data = av_malloc(size);
+    if (!data)
+        return AVERROR(ENOMEM);
+
+    dp = 0;
+    for (i = 0; i < frag->nb_units; i++) {
+        CodedBitstreamUnit *unit = &frag->units[i];
+
+        data[dp++] = 0;
+        data[dp++] = 0;
+        data[dp++] = 1;
+
+        for (sp = 0; sp < unit->data_size; sp++)
+            data[dp++] = unit->data[sp];
+    }
+
+    av_assert0(dp == size);
+
+    frag->data      = data;
+    frag->data_size = size;
+
+    return 0;
+}
+
+static void cbs_mpeg2_free_unit(CodedBitstreamUnit *unit)
+{
+    if (MPEG2_START_IS_SLICE(unit->type)) {
+        MPEG2RawSlice *slice = unit->content;
+        av_freep(&slice->data);
+        av_freep(&slice->header.extra_information);
+    } else if (unit->type == MPEG2_START_USER_DATA) {
+        MPEG2RawUserData *user = unit->content;
+        av_freep(&user->user_data);
+    }
+    av_freep(&unit->content);
+}
+
+static void cbs_mpeg2_close(CodedBitstreamContext *ctx)
+{
+    CodedBitstreamMPEG2Context *priv = ctx->priv_data;
+
+    av_freep(&priv->write_buffer);
+}
+
+const CodedBitstreamType ff_cbs_type_mpeg2 = {
+    .codec_id          = AV_CODEC_ID_MPEG2VIDEO,
+
+    .priv_data_size    = sizeof(CodedBitstreamMPEG2Context),
+
+    .split_fragment    = &cbs_mpeg2_split_fragment,
+    .read_unit         = &cbs_mpeg2_read_unit,
+    .write_unit        = &cbs_mpeg2_write_unit,
+    .assemble_fragment = &cbs_mpeg2_assemble_fragment,
+
+    .free_unit         = &cbs_mpeg2_free_unit,
+    .close             = &cbs_mpeg2_close,
+};
diff --git a/libavcodec/cbs_mpeg2.h b/libavcodec/cbs_mpeg2.h
new file mode 100644
index 0000000000..a8f12b2e75
--- /dev/null
+++ b/libavcodec/cbs_mpeg2.h
@@ -0,0 +1,224 @@
+/*
+ * 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_CBS_MPEG2_H
+#define AVCODEC_CBS_MPEG2_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+
+enum {
+    MPEG2_START_PICTURE         = 0x00,
+    MPEG2_START_SLICE_MIN       = 0x01,
+    MPEG2_START_SLICE_MAX       = 0xaf,
+    MPEG2_START_USER_DATA       = 0xb2,
+    MPEG2_START_SEQUENCE_HEADER = 0xb3,
+    MPEG2_START_SEQUENCE_ERROR  = 0xb4,
+    MPEG2_START_EXTENSION       = 0xb5,
+    MPEG2_START_SEQUENCE_END    = 0xb7,
+    MPEG2_START_GROUP           = 0xb8,
+};
+
+#define MPEG2_START_IS_SLICE(type) \
+    ((type) >= MPEG2_START_SLICE_MIN && \
+     (type) <= MPEG2_START_SLICE_MAX)
+
+enum {
+    MPEG2_EXTENSION_SEQUENCE                  = 0x1,
+    MPEG2_EXTENSION_SEQUENCE_DISPLAY          = 0x2,
+    MPEG2_EXTENSION_QUANT_MATRIX              = 0x3,
+    MPEG2_EXTENSION_COPYRIGHT                 = 0x4,
+    MPEG2_EXTENSION_SEQUENCE_SCALABLE         = 0x5,
+    MPEG2_EXTENSION_PICTURE_DISPLAY           = 0x7,
+    MPEG2_EXTENSION_PICTURE_CODING            = 0x8,
+    MPEG2_EXTENSION_PICTURE_SPATIAL_SCALABLE  = 0x9,
+    MPEG2_EXTENSION_PICTURE_TEMPORAL_SCALABLE = 0xa,
+    MPEG2_EXTENSION_CAMAERA_PARAMETERS        = 0xb,
+    MPEG2_EXTENSION_ITU_T                     = 0xc,
+};
+
+
+typedef struct MPEG2RawSequenceHeader {
+    uint8_t sequence_header_code;
+
+    uint16_t horizontal_size_value;
+    uint16_t vertical_size_value;
+    uint8_t aspect_ratio_information;
+    uint8_t frame_rate_code;
+    uint32_t bit_rate_value;
+    uint16_t vbv_buffer_size_value;
+    uint8_t constrained_parameters_flag;
+
+    uint8_t load_intra_quantiser_matrix;
+    uint8_t intra_quantiser_matrix[64];
+    uint8_t load_non_intra_quantiser_matrix;
+    uint8_t non_intra_quantiser_matrix[64];
+} MPEG2RawSequenceHeader;
+
+typedef struct MPEG2RawUserData {
+    uint8_t user_data_start_code;
+
+    uint8_t *user_data;
+    size_t user_data_length;
+} MPEG2RawUserData;
+
+typedef struct MPEG2RawSequenceExtension {
+    uint8_t profile_and_level_indication;
+    uint8_t progressive_sequence;
+    uint8_t chroma_format;
+    uint8_t horizontal_size_extension;
+    uint8_t vertical_size_extension;
+    uint16_t bit_rate_extension;
+    uint8_t vbv_buffer_size_extension;
+    uint8_t low_delay;
+    uint8_t frame_rate_extension_n;
+    uint8_t frame_rate_extension_d;
+} MPEG2RawSequenceExtension;
+
+typedef struct MPEG2RawSequenceDisplayExtension {
+    uint8_t video_format;
+
+    uint8_t colour_description;
+    uint8_t colour_primaries;
+    uint8_t transfer_characteristics;
+    uint8_t matrix_coefficients;
+
+    uint16_t display_horizontal_size;
+    uint16_t display_vertical_size;
+} MPEG2RawSequenceDisplayExtension;
+
+typedef struct MPEG2RawGroupOfPicturesHeader {
+    uint8_t group_start_code;
+
+    uint32_t time_code;
+    uint8_t closed_gop;
+    uint8_t broken_link;
+} MPEG2RawGroupOfPicturesHeader;
+
+typedef struct MPEG2RawPictureHeader {
+    uint8_t picture_start_code;
+
+    uint16_t temporal_reference;
+    uint8_t picture_coding_type;
+    uint16_t vbv_delay;
+
+    uint8_t full_pel_forward_vector;
+    uint8_t forward_f_code;
+    uint8_t full_pel_backward_vector;
+    uint8_t backward_f_code;
+
+    uint8_t extra_bit_picture;
+} MPEG2RawPictureHeader;
+
+typedef struct MPEG2RawPictureCodingExtension {
+    uint8_t f_code[2][2];
+
+    uint8_t intra_dc_precision;
+    uint8_t picture_structure;
+    uint8_t top_field_first;
+    uint8_t frame_pred_frame_dct;
+    uint8_t concealment_motion_vectors;
+    uint8_t q_scale_type;
+    uint8_t intra_vlc_format;
+    uint8_t alternate_scan;
+    uint8_t repeat_first_field;
+    uint8_t chroma_420_type;
+    uint8_t progressive_frame;
+
+    uint8_t composite_display_flag;
+    uint8_t v_axis;
+    uint8_t field_sequence;
+    uint8_t sub_carrier;
+    uint8_t burst_amplitude;
+    uint8_t sub_carrier_phase;
+} MPEG2RawPictureCodingExtension;
+
+typedef struct MPEG2RawQuantMatrixExtension {
+    uint8_t load_intra_quantiser_matrix;
+    uint8_t intra_quantiser_matrix[64];
+    uint8_t load_non_intra_quantiser_matrix;
+    uint8_t non_intra_quantiser_matrix[64];
+    uint8_t load_chroma_intra_quantiser_matrix;
+    uint8_t chroma_intra_quantiser_matrix[64];
+    uint8_t load_chroma_non_intra_quantiser_matrix;
+    uint8_t chroma_non_intra_quantiser_matrix[64];
+} MPEG2RawQuantMatrixExtension;
+
+typedef struct MPEG2RawPictureDisplayExtension {
+    uint16_t frame_centre_horizontal_offset[3];
+    uint16_t frame_centre_vertical_offset[3];
+} MPEG2RawPictureDisplayExtension;
+
+typedef struct MPEG2RawExtensionData {
+    uint8_t extension_start_code;
+    uint8_t extension_start_code_identifier;
+
+    union {
+        MPEG2RawSequenceExtension sequence;
+        MPEG2RawSequenceDisplayExtension sequence_display;
+        MPEG2RawQuantMatrixExtension quant_matrix;
+        MPEG2RawPictureCodingExtension picture_coding;
+        MPEG2RawPictureDisplayExtension picture_display;
+    } data;
+} MPEG2RawExtensionData;
+
+typedef struct MPEG2RawSliceHeader {
+    uint8_t slice_vertical_position;
+
+    uint8_t slice_vertical_position_extension;
+    uint8_t priority_breakpoint;
+
+    uint8_t quantiser_scale_code;
+
+    uint8_t slice_extension_flag;
+    uint8_t intra_slice;
+    uint8_t slice_picture_id_enable;
+    uint8_t slice_picture_id;
+
+    uint8_t extra_bit_slice;
+
+    size_t extra_information_length;
+    uint8_t *extra_information;
+} MPEG2RawSliceHeader;
+
+typedef struct MPEG2RawSlice {
+    MPEG2RawSliceHeader header;
+
+    uint8_t *data;
+    size_t   data_size;
+    int      data_bit_start;
+} MPEG2RawSlice;
+
+
+typedef struct CodedBitstreamMPEG2Context {
+    // Elements stored in headers which are required for other decoding.
+    uint16_t horizontal_size;
+    uint16_t vertical_size;
+    uint8_t scalable;
+    uint8_t scalable_mode;
+    uint8_t progressive_sequence;
+    uint8_t number_of_frame_centre_offsets;
+
+    // Write buffer.
+    uint8_t *write_buffer;
+    size_t write_buffer_size;
+} CodedBitstreamMPEG2Context;
+
+
+#endif /* AVCODEC_CBS_MPEG2_H */
diff --git a/libavcodec/cbs_mpeg2_syntax_template.c b/libavcodec/cbs_mpeg2_syntax_template.c
new file mode 100644
index 0000000000..90dde26aed
--- /dev/null
+++ b/libavcodec/cbs_mpeg2_syntax_template.c
@@ -0,0 +1,384 @@
+/*
+ * 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
+ */
+
+static int FUNC(sequence_header)(CodedBitstreamContext *ctx, RWContext *rw,
+                                 MPEG2RawSequenceHeader *current)
+{
+    CodedBitstreamMPEG2Context *mpeg2 = ctx->priv_data;
+    int err, i;
+
+    HEADER("Sequence Header");
+
+    ui(8,  sequence_header_code);
+
+    ui(12, horizontal_size_value);
+    ui(12, vertical_size_value);
+
+    mpeg2->horizontal_size = current->horizontal_size_value;
+    mpeg2->vertical_size   = current->vertical_size_value;
+
+    ui(4,  aspect_ratio_information);
+    ui(4,  frame_rate_code);
+    ui(18, bit_rate_value);
+
+    marker_bit();
+
+    ui(10, vbv_buffer_size_value);
+    ui(1,  constrained_parameters_flag);
+
+    ui(1, load_intra_quantiser_matrix);
+    if (current->load_intra_quantiser_matrix) {
+        for (i = 0; i < 64; i++)
+            ui(8, intra_quantiser_matrix[i]);
+    }
+
+    ui(1, load_non_intra_quantiser_matrix);
+    if (current->load_non_intra_quantiser_matrix) {
+        for (i = 0; i < 64; i++)
+            ui(8, non_intra_quantiser_matrix[i]);
+    }
+
+    return 0;
+}
+
+static int FUNC(user_data)(CodedBitstreamContext *ctx, RWContext *rw,
+                           MPEG2RawUserData *current)
+{
+    size_t k;
+    int err;
+
+    HEADER("User Data");
+
+    ui(8, user_data_start_code);
+
+#ifdef READ
+    k = get_bits_left(rw);
+    av_assert0(k % 8 == 0);
+    current->user_data_length = k /= 8;
+    if (k > 0) {
+        current->user_data = av_malloc(k);
+        if (!current->user_data)
+            return AVERROR(ENOMEM);
+    }
+#endif
+
+    for (k = 0; k < current->user_data_length; k++)
+        xui(8, user_data, current->user_data[k]);
+
+    return 0;
+}
+
+static int FUNC(sequence_extension)(CodedBitstreamContext *ctx, RWContext *rw,
+                                    MPEG2RawSequenceExtension *current)
+{
+    CodedBitstreamMPEG2Context *mpeg2 = ctx->priv_data;
+    int err;
+
+    HEADER("Sequence Extension");
+
+    ui(8,  profile_and_level_indication);
+    ui(1,  progressive_sequence);
+    ui(2,  chroma_format);
+    ui(2,  horizontal_size_extension);
+    ui(2,  vertical_size_extension);
+
+    mpeg2->horizontal_size = (mpeg2->horizontal_size & 0xfff) |
+        current->horizontal_size_extension << 12;
+    mpeg2->vertical_size = (mpeg2->vertical_size & 0xfff) |
+        current->vertical_size_extension << 12;
+    mpeg2->progressive_sequence = current->progressive_sequence;
+
+    ui(12, bit_rate_extension);
+    marker_bit();
+    ui(8,  vbv_buffer_size_extension);
+    ui(1,  low_delay);
+    ui(2,  frame_rate_extension_n);
+    ui(5,  frame_rate_extension_d);
+
+    return 0;
+}
+
+static int FUNC(sequence_display_extension)(CodedBitstreamContext *ctx, RWContext *rw,
+                                            MPEG2RawSequenceDisplayExtension *current)
+{
+    int err;
+
+    HEADER("Sequence Display Extension");
+
+    ui(3, video_format);
+
+    ui(1, colour_description);
+    if (current->colour_description) {
+        ui(8, colour_primaries);
+        ui(8, transfer_characteristics);
+        ui(8, matrix_coefficients);
+    }
+
+    ui(14, display_horizontal_size);
+    marker_bit();
+    ui(14, display_vertical_size);
+
+    return 0;
+}
+
+static int FUNC(group_of_pictures_header)(CodedBitstreamContext *ctx, RWContext *rw,
+                                          MPEG2RawGroupOfPicturesHeader *current)
+{
+    int err;
+
+    HEADER("Group of Pictures Header");
+
+    ui(8,  group_start_code);
+
+    ui(25, time_code);
+    ui(1,  closed_gop);
+    ui(1,  broken_link);
+
+    return 0;
+}
+
+static int FUNC(picture_header)(CodedBitstreamContext *ctx, RWContext *rw,
+                                MPEG2RawPictureHeader *current)
+{
+    int err;
+
+    HEADER("Picture Header");
+
+    ui(8,  picture_start_code);
+
+    ui(10, temporal_reference);
+    ui(3,  picture_coding_type);
+    ui(16, vbv_delay);
+
+    if (current->picture_coding_type == 2 ||
+        current->picture_coding_type == 3) {
+        ui(1, full_pel_forward_vector);
+        ui(3, forward_f_code);
+    }
+
+    if (current->picture_coding_type == 3) {
+        ui(1, full_pel_backward_vector);
+        ui(3, backward_f_code);
+    }
+
+    ui(1, extra_bit_picture);
+
+    return 0;
+}
+
+static int FUNC(picture_coding_extension)(CodedBitstreamContext *ctx, RWContext *rw,
+                                          MPEG2RawPictureCodingExtension *current)
+{
+    CodedBitstreamMPEG2Context *mpeg2 = ctx->priv_data;
+    int err;
+
+    HEADER("Picture Coding Extension");
+
+    ui(4, f_code[0][0]);
+    ui(4, f_code[0][1]);
+    ui(4, f_code[1][0]);
+    ui(4, f_code[1][1]);
+
+    ui(2, intra_dc_precision);
+    ui(2, picture_structure);
+    ui(1, top_field_first);
+    ui(1, frame_pred_frame_dct);
+    ui(1, concealment_motion_vectors);
+    ui(1, q_scale_type);
+    ui(1, intra_vlc_format);
+    ui(1, alternate_scan);
+    ui(1, repeat_first_field);
+    ui(1, chroma_420_type);
+    ui(1, progressive_frame);
+
+    if (mpeg2->progressive_sequence) {
+        if (current->repeat_first_field) {
+            if (current->top_field_first)
+                mpeg2->number_of_frame_centre_offsets = 3;
+            else
+                mpeg2->number_of_frame_centre_offsets = 2;
+        } else {
+            mpeg2->number_of_frame_centre_offsets = 1;
+        }
+    } else {
+        if (current->picture_structure == 1 || // Top field.
+            current->picture_structure == 2) { // Bottom field.
+            mpeg2->number_of_frame_centre_offsets = 1;
+        } else {
+            if (current->repeat_first_field)
+                mpeg2->number_of_frame_centre_offsets = 3;
+            else
+                mpeg2->number_of_frame_centre_offsets = 2;
+        }
+    }
+
+    ui(1, composite_display_flag);
+    if (current->composite_display_flag) {
+        ui(1, v_axis);
+        ui(3, field_sequence);
+        ui(1, sub_carrier);
+        ui(7, burst_amplitude);
+        ui(8, sub_carrier_phase);
+    }
+
+    return 0;
+}
+
+static int FUNC(quant_matrix_extension)(CodedBitstreamContext *ctx, RWContext *rw,
+                                        MPEG2RawQuantMatrixExtension *current)
+{
+    int err, i;
+
+    HEADER("Quant Matrix Extension");
+
+    ui(1, load_intra_quantiser_matrix);
+    if (current->load_intra_quantiser_matrix) {
+        for (i = 0; i < 64; i++)
+            ui(8, intra_quantiser_matrix[i]);
+    }
+
+    ui(1, load_non_intra_quantiser_matrix);
+    if (current->load_non_intra_quantiser_matrix) {
+        for (i = 0; i < 64; i++)
+            ui(8, non_intra_quantiser_matrix[i]);
+    }
+
+    ui(1, load_chroma_intra_quantiser_matrix);
+    if (current->load_chroma_intra_quantiser_matrix) {
+        for (i = 0; i < 64; i++)
+            ui(8, intra_quantiser_matrix[i]);
+    }
+
+    ui(1, load_chroma_non_intra_quantiser_matrix);
+    if (current->load_chroma_non_intra_quantiser_matrix) {
+        for (i = 0; i < 64; i++)
+            ui(8, chroma_non_intra_quantiser_matrix[i]);
+    }
+
+    return 0;
+}
+
+static int FUNC(picture_display_extension)(CodedBitstreamContext *ctx, RWContext *rw,
+                                           MPEG2RawPictureDisplayExtension *current)
+{
+    CodedBitstreamMPEG2Context *mpeg2 = ctx->priv_data;
+    int err, i;
+
+    HEADER("Picture Display Extension");
+
+    for (i = 0; i < mpeg2->number_of_frame_centre_offsets; i++) {
+        ui(16, frame_centre_horizontal_offset[i]);
+        marker_bit();
+        ui(16, frame_centre_vertical_offset[i]);
+        marker_bit();
+    }
+
+    return 0;
+}
+
+static int FUNC(extension_data)(CodedBitstreamContext *ctx, RWContext *rw,
+                                MPEG2RawExtensionData *current)
+{
+    int err;
+
+    HEADER("Extension Data");
+
+    ui(8, extension_start_code);
+    ui(4, extension_start_code_identifier);
+
+    switch (current->extension_start_code_identifier) {
+    case 1:
+        return FUNC(sequence_extension)
+            (ctx, rw, &current->data.sequence);
+    case 2:
+        return FUNC(sequence_display_extension)
+            (ctx, rw, &current->data.sequence_display);
+    case 3:
+        return FUNC(quant_matrix_extension)
+            (ctx, rw, &current->data.quant_matrix);
+    case 7:
+        return FUNC(picture_display_extension)
+            (ctx, rw, &current->data.picture_display);
+    case 8:
+        return FUNC(picture_coding_extension)
+            (ctx, rw, &current->data.picture_coding);
+    default:
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid extension ID %d.\n",
+               current->extension_start_code_identifier);
+        return AVERROR_INVALIDDATA;
+    }
+}
+
+static int FUNC(slice_header)(CodedBitstreamContext *ctx, RWContext *rw,
+                              MPEG2RawSliceHeader *current)
+{
+    CodedBitstreamMPEG2Context *mpeg2 = ctx->priv_data;
+    int err;
+
+    HEADER("Slice Header");
+
+    ui(8, slice_vertical_position);
+
+    if (mpeg2->vertical_size > 2800)
+        ui(3, slice_vertical_position_extension);
+    if (mpeg2->scalable) {
+        if (mpeg2->scalable_mode == 0)
+            ui(7, priority_breakpoint);
+    }
+
+    ui(5, quantiser_scale_code);
+
+    if (nextbits(1, 1, current->slice_extension_flag)) {
+        ui(1, slice_extension_flag);
+        ui(1, intra_slice);
+        ui(1, slice_picture_id_enable);
+        ui(6, slice_picture_id);
+
+        {
+            size_t k;
+#ifdef READ
+            GetBitContext start;
+            uint8_t bit;
+            start = *rw;
+            for (k = 0; nextbits(1, 1, bit); k++)
+                skip_bits(rw, 8);
+            current->extra_information_length = k;
+            if (k > 0) {
+                *rw = start;
+                current->extra_information =
+                    av_malloc(current->extra_information_length);
+                if (!current->extra_information)
+                    return AVERROR(ENOMEM);
+                for (k = 0; k < current->extra_information_length; k++) {
+                    xui(1, extra_bit_slice, bit);
+                    xui(8, extra_information_slice,
+                        current->extra_information[k]);
+                }
+            }
+#else
+            for (k = 0; k < current->extra_information_length; k++) {
+                xui(1, extra_bit_slice, 1);
+                xui(8, extra_information_slice, current->extra_information[k]);
+            }
+#endif
+        }
+    }
+    ui(1, extra_bit_slice);
+
+    return 0;
+}