libavcodec/cbs_mpeg2.c - manifest_repos/ffmpeg - Git at Google

 /*
  * 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 SUBSCRIPTS(subs, ...) (subs > 0 ? ((int[subs + 1]){ subs, __VA_ARGS__ }) : NULL)

 #define ui(width, name) \
         xui(width, name, current->name, 0, MAX_UINT_BITS(width), 0, )
 #define uir(width, name) \
         xui(width, name, current->name, 1, MAX_UINT_BITS(width), 0, )
 #define uis(width, name, subs, ...) \
         xui(width, name, current->name, 0, MAX_UINT_BITS(width), subs, __VA_ARGS__)
 #define uirs(width, name, subs, ...) \
         xui(width, name, current->name, 1, MAX_UINT_BITS(width), subs, __VA_ARGS__)
 #define xui(width, name, var, range_min, range_max, subs, ...) \
         xuia(width, #name, var, range_min, range_max, subs, __VA_ARGS__)
 #define sis(width, name, subs, ...) \
         xsi(width, name, current->name, subs, __VA_ARGS__)

 #define marker_bit() \
         bit("marker_bit", 1)
 #define bit(string, value) do { \
         av_unused uint32_t bit = value; \
         xuia(1, string, bit, value, value, 0, ); \
     } while (0)


 #define READ
 #define READWRITE read
 #define RWContext GetBitContext

 #define xuia(width, string, var, range_min, range_max, subs, ...) do { \
         uint32_t value; \
         CHECK(ff_cbs_read_unsigned(ctx, rw, width, string, \
                                    SUBSCRIPTS(subs, __VA_ARGS__), \
                                    &value, range_min, range_max)); \
         var = value; \
     } while (0)

 #define xsi(width, name, var, subs, ...) do { \
         int32_t value; \
         CHECK(ff_cbs_read_signed(ctx, rw, width, #name, \
                                  SUBSCRIPTS(subs, __VA_ARGS__), &value, \
                                  MIN_INT_BITS(width), \
                                  MAX_INT_BITS(width))); \
         var = value; \
     } while (0)

 #define nextbits(width, compare, var) \
     (get_bits_left(rw) >= width && \
      (var = show_bits(rw, width)) == (compare))

 #define infer(name, value) do { \
         current->name = value; \
     } while (0)

 #include "cbs_mpeg2_syntax_template.c"

 #undef READ
 #undef READWRITE
 #undef RWContext
 #undef xuia
 #undef xsi
 #undef nextbits
 #undef infer


 #define WRITE
 #define READWRITE write
 #define RWContext PutBitContext

 #define xuia(width, string, var, range_min, range_max, subs, ...) do { \
         CHECK(ff_cbs_write_unsigned(ctx, rw, width, string, \
                                     SUBSCRIPTS(subs, __VA_ARGS__), \
                                     var, range_min, range_max)); \
     } while (0)

 #define xsi(width, name, var, subs, ...) do { \
         CHECK(ff_cbs_write_signed(ctx, rw, width, #name, \
                                   SUBSCRIPTS(subs, __VA_ARGS__), var, \
                                   MIN_INT_BITS(width), \
                                   MAX_INT_BITS(width))); \
     } while (0)

 #define nextbits(width, compare, var) (var)

 #define infer(name, value) do { \
         if (current->name != (value)) { \
             av_log(ctx->log_ctx, AV_LOG_WARNING, "Warning: " \
                    "%s does not match inferred value: " \
                    "%"PRId64", but should be %"PRId64".\n", \
                    #name, (int64_t)current->name, (int64_t)(value)); \
         } \
     } while (0)

 #include "cbs_mpeg2_syntax_template.c"

 #undef WRITE
 #undef READWRITE
 #undef RWContext
 #undef xuia
 #undef xsi
 #undef nextbits
 #undef infer


 static int cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx,
                                     CodedBitstreamFragment *frag,
                                     int header)
 {
     const uint8_t *start, *end;
     CodedBitstreamUnitType unit_type;
     uint32_t start_code = -1;
     size_t unit_size;
     int err, i, final = 0;

     start = avpriv_find_start_code(frag->data, frag->data + frag->data_size,
                                    &start_code);
     if (start_code >> 8 != 0x000001) {
         // No start code found.
         return AVERROR_INVALIDDATA;
     }

     for (i = 0;; i++) {
         unit_type = start_code & 0xff;

         if (start == frag->data + frag->data_size) {
             // The last four bytes form a start code which constitutes
             // a unit of its own.  In this situation avpriv_find_start_code
             // won't modify start_code at all so modify start_code so that
             // the next unit will be treated as the last unit.
             start_code = 0;
         }

         end = avpriv_find_start_code(start--, frag->data + frag->data_size,
                                      &start_code);

         // start points to the byte containing the start_code_identifier
         // (may be the last byte of fragment->data); end points to the byte
         // following the byte containing the start code identifier (or to
         // the end of fragment->data).
         if (start_code >> 8 == 0x000001) {
             // Unit runs from start to the beginning of the start code
             // pointed to by end (including any padding zeroes).
             unit_size = (end - 4) - start;
         } else {
            // We didn't find a start code, so this is the final unit.
            unit_size = end - start;
            final     = 1;
         }

         err = ff_cbs_insert_unit_data(frag, i, unit_type, (uint8_t*)start,
                                       unit_size, frag->data_ref);
         if (err < 0)
             return err;

         if (final)
             break;

         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;

     err = ff_cbs_alloc_unit_content2(ctx, unit);
     if (err < 0)
         return err;

     if (MPEG2_START_IS_SLICE(unit->type)) {
         MPEG2RawSlice *slice = unit->content;
         int pos, len;

         err = cbs_mpeg2_read_slice_header(ctx, &gbc, &slice->header);
         if (err < 0)
             return err;

         if (!get_bits_left(&gbc))
             return AVERROR_INVALIDDATA;

         pos = get_bits_count(&gbc);
         len = unit->data_size;

         slice->data_size = len - pos / 8;
         slice->data_ref  = av_buffer_ref(unit->data_ref);
         if (!slice->data_ref)
             return AVERROR(ENOMEM);
         slice->data = unit->data + pos / 8;

         slice->data_bit_start = pos % 8;

     } else {
         switch (unit->type) {
 #define START(start_code, type, read_func, free_func) \
         case start_code: \
             { \
                 type *header = unit->content; \
                 err = cbs_mpeg2_read_ ## read_func(ctx, &gbc, header); \
                 if (err < 0) \
                     return err; \
             } \
             break;
             START(MPEG2_START_PICTURE,   MPEG2RawPictureHeader,
                   picture_header,           &cbs_mpeg2_free_picture_header);
             START(MPEG2_START_USER_DATA, MPEG2RawUserData,
                   user_data,                &cbs_mpeg2_free_user_data);
             START(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader,
                   sequence_header,          NULL);
             START(MPEG2_START_EXTENSION, MPEG2RawExtensionData,
                   extension_data,           NULL);
             START(MPEG2_START_GROUP,     MPEG2RawGroupOfPicturesHeader,
                   group_of_pictures_header, NULL);
             START(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd,
                   sequence_end,             NULL);
 #undef START
         default:
             return AVERROR(ENOSYS);
         }
     }

     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(MPEG2_START_PICTURE,         MPEG2RawPictureHeader,  picture_header);
         START(MPEG2_START_USER_DATA,       MPEG2RawUserData,       user_data);
         START(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader, sequence_header);
         START(MPEG2_START_EXTENSION,       MPEG2RawExtensionData,  extension_data);
         START(MPEG2_START_GROUP,           MPEG2RawGroupOfPicturesHeader,
                                                          group_of_pictures_header);
         START(MPEG2_START_SEQUENCE_END,    MPEG2RawSequenceEnd,    sequence_end);
 #undef START
     default:
         av_log(ctx->log_ctx, AV_LOG_ERROR, "Write unimplemented for start "
                "code %02"PRIx32".\n", unit->type);
         return AVERROR_PATCHWELCOME;
     }

     return err;
 }

 static int cbs_mpeg2_write_slice(CodedBitstreamContext *ctx,
                                  CodedBitstreamUnit *unit,
                                  PutBitContext *pbc)
 {
     MPEG2RawSlice *slice = unit->content;
     int err;

     err = cbs_mpeg2_write_slice_header(ctx, pbc, &slice->header);
     if (err < 0)
         return err;

     if (slice->data) {
         size_t rest = slice->data_size - (slice->data_bit_start + 7) / 8;
         uint8_t *pos = slice->data + slice->data_bit_start / 8;

         av_assert0(slice->data_bit_start >= 0 &&
                    slice->data_size > slice->data_bit_start / 8);

         if (slice->data_size * 8 + 8 > put_bits_left(pbc))
             return AVERROR(ENOSPC);

         // First copy the remaining bits of the first byte
         if (slice->data_bit_start % 8)
             put_bits(pbc, 8 - slice->data_bit_start % 8,
                      *pos++ & MAX_UINT_BITS(8 - slice->data_bit_start % 8));

         if (put_bits_count(pbc) % 8 == 0) {
             // If the writer is aligned at this point,
             // memcpy can be used to improve performance.
             // This is the normal case.
             flush_put_bits(pbc);
             memcpy(put_bits_ptr(pbc), pos, rest);
             skip_put_bytes(pbc, rest);
         } else {
             // If not, we have to copy manually:
             for (; rest > 3; rest -= 4, pos += 4)
                 put_bits32(pbc, AV_RB32(pos));

             for (; rest; rest--, pos++)
                 put_bits(pbc, 8, *pos);

             // Align with zeros
             put_bits(pbc, 8 - put_bits_count(pbc) % 8, 0);
         }
     }

     return 0;
 }

 static int cbs_mpeg2_write_unit(CodedBitstreamContext *ctx,
                                 CodedBitstreamUnit *unit,
                                 PutBitContext *pbc)
 {
     if (MPEG2_START_IS_SLICE(unit->type))
         return cbs_mpeg2_write_slice (ctx, unit, pbc);
     else
         return cbs_mpeg2_write_header(ctx, unit, pbc);
 }

 static int cbs_mpeg2_assemble_fragment(CodedBitstreamContext *ctx,
                                        CodedBitstreamFragment *frag)
 {
     uint8_t *data;
     size_t size, dp;
     int i;

     size = 0;
     for (i = 0; i < frag->nb_units; i++)
         size += 3 + frag->units[i].data_size;

     frag->data_ref = av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
     if (!frag->data_ref)
         return AVERROR(ENOMEM);
     data = frag->data_ref->data;

     dp = 0;
     for (i = 0; i < frag->nb_units; i++) {
         CodedBitstreamUnit *unit = &frag->units[i];

         data[dp++] = 0;
         data[dp++] = 0;
         data[dp++] = 1;

         memcpy(data + dp, unit->data, unit->data_size);
         dp += unit->data_size;
     }

     av_assert0(dp == size);

     memset(data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
     frag->data      = data;
     frag->data_size = size;

     return 0;
 }

 static const CodedBitstreamUnitTypeDescriptor cbs_mpeg2_unit_types[] = {
     CBS_UNIT_TYPE_INTERNAL_REF(MPEG2_START_PICTURE, MPEG2RawPictureHeader,
                                extra_information_picture.extra_information),

     {
         .nb_unit_types         = CBS_UNIT_TYPE_RANGE,
         .unit_type_range_start = 0x01,
         .unit_type_range_end   = 0xaf,

         .content_type   = CBS_CONTENT_TYPE_INTERNAL_REFS,
         .content_size   = sizeof(MPEG2RawSlice),
         .nb_ref_offsets = 2,
         .ref_offsets    = { offsetof(MPEG2RawSlice, header.extra_information_slice.extra_information),
                             offsetof(MPEG2RawSlice, data) },
     },

     CBS_UNIT_TYPE_INTERNAL_REF(MPEG2_START_USER_DATA, MPEG2RawUserData,
                                user_data),

     CBS_UNIT_TYPE_POD(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader),
     CBS_UNIT_TYPE_POD(MPEG2_START_EXTENSION,       MPEG2RawExtensionData),
     CBS_UNIT_TYPE_POD(MPEG2_START_SEQUENCE_END,    MPEG2RawSequenceEnd),
     CBS_UNIT_TYPE_POD(MPEG2_START_GROUP,           MPEG2RawGroupOfPicturesHeader),

     CBS_UNIT_TYPE_END_OF_LIST
 };

 const CodedBitstreamType ff_cbs_type_mpeg2 = {
     .codec_id          = AV_CODEC_ID_MPEG2VIDEO,

     .priv_data_size    = sizeof(CodedBitstreamMPEG2Context),

     .unit_types        = cbs_mpeg2_unit_types,

     .split_fragment    = &cbs_mpeg2_split_fragment,
     .read_unit         = &cbs_mpeg2_read_unit,
     .write_unit        = &cbs_mpeg2_write_unit,
     .assemble_fragment = &cbs_mpeg2_assemble_fragment,
 };
	/*
	* 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 SUBSCRIPTS(subs, ...) (subs > 0 ? ((int[subs + 1]){ subs, __VA_ARGS__ }) : NULL)

	#define ui(width, name) \
	xui(width, name, current->name, 0, MAX_UINT_BITS(width), 0, )
	#define uir(width, name) \
	xui(width, name, current->name, 1, MAX_UINT_BITS(width), 0, )
	#define uis(width, name, subs, ...) \
	xui(width, name, current->name, 0, MAX_UINT_BITS(width), subs, __VA_ARGS__)
	#define uirs(width, name, subs, ...) \
	xui(width, name, current->name, 1, MAX_UINT_BITS(width), subs, __VA_ARGS__)
	#define xui(width, name, var, range_min, range_max, subs, ...) \
	xuia(width, #name, var, range_min, range_max, subs, __VA_ARGS__)
	#define sis(width, name, subs, ...) \
	xsi(width, name, current->name, subs, __VA_ARGS__)

	#define marker_bit() \
	bit("marker_bit", 1)
	#define bit(string, value) do { \
	av_unused uint32_t bit = value; \
	xuia(1, string, bit, value, value, 0, ); \
	} while (0)


	#define READ
	#define READWRITE read
	#define RWContext GetBitContext

	#define xuia(width, string, var, range_min, range_max, subs, ...) do { \
	uint32_t value; \
	CHECK(ff_cbs_read_unsigned(ctx, rw, width, string, \
	SUBSCRIPTS(subs, __VA_ARGS__), \
	&value, range_min, range_max)); \
	var = value; \
	} while (0)

	#define xsi(width, name, var, subs, ...) do { \
	int32_t value; \
	CHECK(ff_cbs_read_signed(ctx, rw, width, #name, \
	SUBSCRIPTS(subs, __VA_ARGS__), &value, \
	MIN_INT_BITS(width), \
	MAX_INT_BITS(width))); \
	var = value; \
	} while (0)

	#define nextbits(width, compare, var) \
	(get_bits_left(rw) >= width && \
	(var = show_bits(rw, width)) == (compare))

	#define infer(name, value) do { \
	current->name = value; \
	} while (0)

	#include "cbs_mpeg2_syntax_template.c"

	#undef READ
	#undef READWRITE
	#undef RWContext
	#undef xuia
	#undef xsi
	#undef nextbits
	#undef infer


	#define WRITE
	#define READWRITE write
	#define RWContext PutBitContext

	#define xuia(width, string, var, range_min, range_max, subs, ...) do { \
	CHECK(ff_cbs_write_unsigned(ctx, rw, width, string, \
	SUBSCRIPTS(subs, __VA_ARGS__), \
	var, range_min, range_max)); \
	} while (0)

	#define xsi(width, name, var, subs, ...) do { \
	CHECK(ff_cbs_write_signed(ctx, rw, width, #name, \
	SUBSCRIPTS(subs, __VA_ARGS__), var, \
	MIN_INT_BITS(width), \
	MAX_INT_BITS(width))); \
	} while (0)

	#define nextbits(width, compare, var) (var)

	#define infer(name, value) do { \
	if (current->name != (value)) { \
	av_log(ctx->log_ctx, AV_LOG_WARNING, "Warning: " \
	"%s does not match inferred value: " \
	"%"PRId64", but should be %"PRId64".\n", \
	#name, (int64_t)current->name, (int64_t)(value)); \
	} \
	} while (0)

	#include "cbs_mpeg2_syntax_template.c"

	#undef WRITE
	#undef READWRITE
	#undef RWContext
	#undef xuia
	#undef xsi
	#undef nextbits
	#undef infer


	static int cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx,
	CodedBitstreamFragment *frag,
	int header)
	{
	const uint8_t start, end;
	CodedBitstreamUnitType unit_type;
	uint32_t start_code = -1;
	size_t unit_size;
	int err, i, final = 0;

	start = avpriv_find_start_code(frag->data, frag->data + frag->data_size,
	&start_code);
	if (start_code >> 8 != 0x000001) {
	// No start code found.
	return AVERROR_INVALIDDATA;
	}

	for (i = 0;; i++) {
	unit_type = start_code & 0xff;

	if (start == frag->data + frag->data_size) {
	// The last four bytes form a start code which constitutes
	// a unit of its own. In this situation avpriv_find_start_code
	// won't modify start_code at all so modify start_code so that
	// the next unit will be treated as the last unit.
	start_code = 0;
	}

	end = avpriv_find_start_code(start--, frag->data + frag->data_size,
	&start_code);

	// start points to the byte containing the start_code_identifier
	// (may be the last byte of fragment->data); end points to the byte
	// following the byte containing the start code identifier (or to
	// the end of fragment->data).
	if (start_code >> 8 == 0x000001) {
	// Unit runs from start to the beginning of the start code
	// pointed to by end (including any padding zeroes).
	unit_size = (end - 4) - start;
	} else {
	// We didn't find a start code, so this is the final unit.
	unit_size = end - start;
	final = 1;
	}

	err = ff_cbs_insert_unit_data(frag, i, unit_type, (uint8_t*)start,
	unit_size, frag->data_ref);
	if (err < 0)
	return err;

	if (final)
	break;

	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;

	err = ff_cbs_alloc_unit_content2(ctx, unit);
	if (err < 0)
	return err;

	if (MPEG2_START_IS_SLICE(unit->type)) {
	MPEG2RawSlice *slice = unit->content;
	int pos, len;

	err = cbs_mpeg2_read_slice_header(ctx, &gbc, &slice->header);
	if (err < 0)
	return err;

	if (!get_bits_left(&gbc))
	return AVERROR_INVALIDDATA;

	pos = get_bits_count(&gbc);
	len = unit->data_size;

	slice->data_size = len - pos / 8;
	slice->data_ref = av_buffer_ref(unit->data_ref);
	if (!slice->data_ref)
	return AVERROR(ENOMEM);
	slice->data = unit->data + pos / 8;

	slice->data_bit_start = pos % 8;

	} else {
	switch (unit->type) {
	#define START(start_code, type, read_func, free_func) \
	case start_code: \
	{ \
	type *header = unit->content; \
	err = cbs_mpeg2_read_ ## read_func(ctx, &gbc, header); \
	if (err < 0) \
	return err; \
	} \
	break;
	START(MPEG2_START_PICTURE, MPEG2RawPictureHeader,
	picture_header, &cbs_mpeg2_free_picture_header);
	START(MPEG2_START_USER_DATA, MPEG2RawUserData,
	user_data, &cbs_mpeg2_free_user_data);
	START(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader,
	sequence_header, NULL);
	START(MPEG2_START_EXTENSION, MPEG2RawExtensionData,
	extension_data, NULL);
	START(MPEG2_START_GROUP, MPEG2RawGroupOfPicturesHeader,
	group_of_pictures_header, NULL);
	START(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd,
	sequence_end, NULL);
	#undef START
	default:
	return AVERROR(ENOSYS);
	}
	}

	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(MPEG2_START_PICTURE, MPEG2RawPictureHeader, picture_header);
	START(MPEG2_START_USER_DATA, MPEG2RawUserData, user_data);
	START(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader, sequence_header);
	START(MPEG2_START_EXTENSION, MPEG2RawExtensionData, extension_data);
	START(MPEG2_START_GROUP, MPEG2RawGroupOfPicturesHeader,
	group_of_pictures_header);
	START(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd, sequence_end);
	#undef START
	default:
	av_log(ctx->log_ctx, AV_LOG_ERROR, "Write unimplemented for start "
	"code %02"PRIx32".\n", unit->type);
	return AVERROR_PATCHWELCOME;
	}

	return err;
	}

	static int cbs_mpeg2_write_slice(CodedBitstreamContext *ctx,
	CodedBitstreamUnit *unit,
	PutBitContext *pbc)
	{
	MPEG2RawSlice *slice = unit->content;
	int err;

	err = cbs_mpeg2_write_slice_header(ctx, pbc, &slice->header);
	if (err < 0)
	return err;

	if (slice->data) {
	size_t rest = slice->data_size - (slice->data_bit_start + 7) / 8;
	uint8_t *pos = slice->data + slice->data_bit_start / 8;

	av_assert0(slice->data_bit_start >= 0 &&
	slice->data_size > slice->data_bit_start / 8);

	if (slice->data_size * 8 + 8 > put_bits_left(pbc))
	return AVERROR(ENOSPC);

	// First copy the remaining bits of the first byte
	if (slice->data_bit_start % 8)
	put_bits(pbc, 8 - slice->data_bit_start % 8,
	*pos++ & MAX_UINT_BITS(8 - slice->data_bit_start % 8));

	if (put_bits_count(pbc) % 8 == 0) {
	// If the writer is aligned at this point,
	// memcpy can be used to improve performance.
	// This is the normal case.
	flush_put_bits(pbc);
	memcpy(put_bits_ptr(pbc), pos, rest);
	skip_put_bytes(pbc, rest);
	} else {
	// If not, we have to copy manually:
	for (; rest > 3; rest -= 4, pos += 4)
	put_bits32(pbc, AV_RB32(pos));

	for (; rest; rest--, pos++)
	put_bits(pbc, 8, *pos);

	// Align with zeros
	put_bits(pbc, 8 - put_bits_count(pbc) % 8, 0);
	}
	}

	return 0;
	}

	static int cbs_mpeg2_write_unit(CodedBitstreamContext *ctx,
	CodedBitstreamUnit *unit,
	PutBitContext *pbc)
	{
	if (MPEG2_START_IS_SLICE(unit->type))
	return cbs_mpeg2_write_slice (ctx, unit, pbc);
	else
	return cbs_mpeg2_write_header(ctx, unit, pbc);
	}

	static int cbs_mpeg2_assemble_fragment(CodedBitstreamContext *ctx,
	CodedBitstreamFragment *frag)
	{
	uint8_t *data;
	size_t size, dp;
	int i;

	size = 0;
	for (i = 0; i < frag->nb_units; i++)
	size += 3 + frag->units[i].data_size;

	frag->data_ref = av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
	if (!frag->data_ref)
	return AVERROR(ENOMEM);
	data = frag->data_ref->data;

	dp = 0;
	for (i = 0; i < frag->nb_units; i++) {
	CodedBitstreamUnit *unit = &frag->units[i];

	data[dp++] = 0;
	data[dp++] = 0;
	data[dp++] = 1;

	memcpy(data + dp, unit->data, unit->data_size);
	dp += unit->data_size;
	}

	av_assert0(dp == size);

	memset(data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
	frag->data = data;
	frag->data_size = size;

	return 0;
	}

	static const CodedBitstreamUnitTypeDescriptor cbs_mpeg2_unit_types[] = {
	CBS_UNIT_TYPE_INTERNAL_REF(MPEG2_START_PICTURE, MPEG2RawPictureHeader,
	extra_information_picture.extra_information),

	{
	.nb_unit_types = CBS_UNIT_TYPE_RANGE,
	.unit_type_range_start = 0x01,
	.unit_type_range_end = 0xaf,

	.content_type = CBS_CONTENT_TYPE_INTERNAL_REFS,
	.content_size = sizeof(MPEG2RawSlice),
	.nb_ref_offsets = 2,
	.ref_offsets = { offsetof(MPEG2RawSlice, header.extra_information_slice.extra_information),
	offsetof(MPEG2RawSlice, data) },
	},

	CBS_UNIT_TYPE_INTERNAL_REF(MPEG2_START_USER_DATA, MPEG2RawUserData,
	user_data),

	CBS_UNIT_TYPE_POD(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader),
	CBS_UNIT_TYPE_POD(MPEG2_START_EXTENSION, MPEG2RawExtensionData),
	CBS_UNIT_TYPE_POD(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd),
	CBS_UNIT_TYPE_POD(MPEG2_START_GROUP, MPEG2RawGroupOfPicturesHeader),

	CBS_UNIT_TYPE_END_OF_LIST
	};

	const CodedBitstreamType ff_cbs_type_mpeg2 = {
	.codec_id = AV_CODEC_ID_MPEG2VIDEO,

	.priv_data_size = sizeof(CodedBitstreamMPEG2Context),

	.unit_types = cbs_mpeg2_unit_types,

	.split_fragment = &cbs_mpeg2_split_fragment,
	.read_unit = &cbs_mpeg2_read_unit,
	.write_unit = &cbs_mpeg2_write_unit,
	.assemble_fragment = &cbs_mpeg2_assemble_fragment,
	};