early-access version 1432

externals/ffmpeg/libavcodec/cbs.c

@@ -0,0 +1,814 @@
+/*
+ * 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 <string.h>
+
+#include "config.h"
+
+#include "libavutil/avassert.h"
+#include "libavutil/buffer.h"
+#include "libavutil/common.h"
+
+#include "cbs.h"
+#include "cbs_internal.h"
+
+
+static const CodedBitstreamType *cbs_type_table[] = {
+#if CONFIG_CBS_AV1
+    &ff_cbs_type_av1,
+#endif
+#if CONFIG_CBS_H264
+    &ff_cbs_type_h264,
+#endif
+#if CONFIG_CBS_H265
+    &ff_cbs_type_h265,
+#endif
+#if CONFIG_CBS_JPEG
+    &ff_cbs_type_jpeg,
+#endif
+#if CONFIG_CBS_MPEG2
+    &ff_cbs_type_mpeg2,
+#endif
+#if CONFIG_CBS_VP9
+    &ff_cbs_type_vp9,
+#endif
+};
+
+const enum AVCodecID ff_cbs_all_codec_ids[] = {
+#if CONFIG_CBS_AV1
+    AV_CODEC_ID_AV1,
+#endif
+#if CONFIG_CBS_H264
+    AV_CODEC_ID_H264,
+#endif
+#if CONFIG_CBS_H265
+    AV_CODEC_ID_H265,
+#endif
+#if CONFIG_CBS_JPEG
+    AV_CODEC_ID_MJPEG,
+#endif
+#if CONFIG_CBS_MPEG2
+    AV_CODEC_ID_MPEG2VIDEO,
+#endif
+#if CONFIG_CBS_VP9
+    AV_CODEC_ID_VP9,
+#endif
+    AV_CODEC_ID_NONE
+};
+
+int ff_cbs_init(CodedBitstreamContext **ctx_ptr,
+                enum AVCodecID codec_id, void *log_ctx)
+{
+    CodedBitstreamContext *ctx;
+    const CodedBitstreamType *type;
+    int i;
+
+    type = NULL;
+    for (i = 0; i < FF_ARRAY_ELEMS(cbs_type_table); i++) {
+        if (cbs_type_table[i]->codec_id == codec_id) {
+            type = cbs_type_table[i];
+            break;
+        }
+    }
+    if (!type)
+        return AVERROR(EINVAL);
+
+    ctx = av_mallocz(sizeof(*ctx));
+    if (!ctx)
+        return AVERROR(ENOMEM);
+
+    ctx->log_ctx = log_ctx;
+    ctx->codec   = type;
+
+    if (type->priv_data_size) {
+        ctx->priv_data = av_mallocz(ctx->codec->priv_data_size);
+        if (!ctx->priv_data) {
+            av_freep(&ctx);
+            return AVERROR(ENOMEM);
+        }
+    }
+
+    ctx->decompose_unit_types = NULL;
+
+    ctx->trace_enable = 0;
+    ctx->trace_level  = AV_LOG_TRACE;
+
+    *ctx_ptr = ctx;
+    return 0;
+}
+
+void ff_cbs_close(CodedBitstreamContext **ctx_ptr)
+{
+    CodedBitstreamContext *ctx = *ctx_ptr;
+
+    if (!ctx)
+        return;
+
+    if (ctx->codec && ctx->codec->close)
+        ctx->codec->close(ctx);
+
+    av_freep(&ctx->write_buffer);
+    av_freep(&ctx->priv_data);
+    av_freep(ctx_ptr);
+}
+
+static void cbs_unit_uninit(CodedBitstreamContext *ctx,
+                            CodedBitstreamUnit *unit)
+{
+    av_buffer_unref(&unit->content_ref);
+    unit->content = NULL;
+
+    av_buffer_unref(&unit->data_ref);
+    unit->data             = NULL;
+    unit->data_size        = 0;
+    unit->data_bit_padding = 0;
+}
+
+void ff_cbs_fragment_reset(CodedBitstreamContext *ctx,
+                           CodedBitstreamFragment *frag)
+{
+    int i;
+
+    for (i = 0; i < frag->nb_units; i++)
+        cbs_unit_uninit(ctx, &frag->units[i]);
+    frag->nb_units = 0;
+
+    av_buffer_unref(&frag->data_ref);
+    frag->data             = NULL;
+    frag->data_size        = 0;
+    frag->data_bit_padding = 0;
+}
+
+void ff_cbs_fragment_free(CodedBitstreamContext *ctx,
+                          CodedBitstreamFragment *frag)
+{
+    ff_cbs_fragment_reset(ctx, frag);
+
+    av_freep(&frag->units);
+    frag->nb_units_allocated = 0;
+}
+
+static int cbs_read_fragment_content(CodedBitstreamContext *ctx,
+                                     CodedBitstreamFragment *frag)
+{
+    int err, i, j;
+
+    for (i = 0; i < frag->nb_units; i++) {
+        CodedBitstreamUnit *unit = &frag->units[i];
+
+        if (ctx->decompose_unit_types) {
+            for (j = 0; j < ctx->nb_decompose_unit_types; j++) {
+                if (ctx->decompose_unit_types[j] == unit->type)
+                    break;
+            }
+            if (j >= ctx->nb_decompose_unit_types)
+                continue;
+        }
+
+        av_buffer_unref(&unit->content_ref);
+        unit->content = NULL;
+
+        av_assert0(unit->data && unit->data_ref);
+
+        err = ctx->codec->read_unit(ctx, unit);
+        if (err == AVERROR(ENOSYS)) {
+            av_log(ctx->log_ctx, AV_LOG_VERBOSE,
+                   "Decomposition unimplemented for unit %d "
+                   "(type %"PRIu32").\n", i, unit->type);
+        } else if (err < 0) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Failed to read unit %d "
+                   "(type %"PRIu32").\n", i, unit->type);
+            return err;
+        }
+    }
+
+    return 0;
+}
+
+static int cbs_fill_fragment_data(CodedBitstreamContext *ctx,
+                                  CodedBitstreamFragment *frag,
+                                  const uint8_t *data, size_t size)
+{
+    av_assert0(!frag->data && !frag->data_ref);
+
+    frag->data_ref =
+        av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
+    if (!frag->data_ref)
+        return AVERROR(ENOMEM);
+
+    frag->data      = frag->data_ref->data;
+    frag->data_size = size;
+
+    memcpy(frag->data, data, size);
+    memset(frag->data + size, 0,
+           AV_INPUT_BUFFER_PADDING_SIZE);
+
+    return 0;
+}
+
+int ff_cbs_read_extradata(CodedBitstreamContext *ctx,
+                          CodedBitstreamFragment *frag,
+                          const AVCodecParameters *par)
+{
+    int err;
+
+    err = cbs_fill_fragment_data(ctx, frag, par->extradata,
+                                 par->extradata_size);
+    if (err < 0)
+        return err;
+
+    err = ctx->codec->split_fragment(ctx, frag, 1);
+    if (err < 0)
+        return err;
+
+    return cbs_read_fragment_content(ctx, frag);
+}
+
+int ff_cbs_read_packet(CodedBitstreamContext *ctx,
+                       CodedBitstreamFragment *frag,
+                       const AVPacket *pkt)
+{
+    int err;
+
+    if (pkt->buf) {
+        frag->data_ref = av_buffer_ref(pkt->buf);
+        if (!frag->data_ref)
+            return AVERROR(ENOMEM);
+
+        frag->data      = pkt->data;
+        frag->data_size = pkt->size;
+
+    } else {
+        err = cbs_fill_fragment_data(ctx, frag, pkt->data, pkt->size);
+        if (err < 0)
+            return err;
+    }
+
+    err = ctx->codec->split_fragment(ctx, frag, 0);
+    if (err < 0)
+        return err;
+
+    return cbs_read_fragment_content(ctx, frag);
+}
+
+int ff_cbs_read(CodedBitstreamContext *ctx,
+                CodedBitstreamFragment *frag,
+                const uint8_t *data, size_t size)
+{
+    int err;
+
+    err = cbs_fill_fragment_data(ctx, frag, data, size);
+    if (err < 0)
+        return err;
+
+    err = ctx->codec->split_fragment(ctx, frag, 0);
+    if (err < 0)
+        return err;
+
+    return cbs_read_fragment_content(ctx, frag);
+}
+
+static int cbs_write_unit_data(CodedBitstreamContext *ctx,
+                               CodedBitstreamUnit *unit)
+{
+    PutBitContext pbc;
+    int ret;
+
+    if (!ctx->write_buffer) {
+        // Initial write buffer size is 1MB.
+        ctx->write_buffer_size = 1024 * 1024;
+
+    reallocate_and_try_again:
+        ret = av_reallocp(&ctx->write_buffer, ctx->write_buffer_size);
+        if (ret < 0) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Unable to allocate a "
+                   "sufficiently large write buffer (last attempt "
+                   "%"SIZE_SPECIFIER" bytes).\n", ctx->write_buffer_size);
+            return ret;
+        }
+    }
+
+    init_put_bits(&pbc, ctx->write_buffer, ctx->write_buffer_size);
+
+    ret = ctx->codec->write_unit(ctx, unit, &pbc);
+    if (ret < 0) {
+        if (ret == AVERROR(ENOSPC)) {
+            // Overflow.
+            if (ctx->write_buffer_size == INT_MAX / 8)
+                return AVERROR(ENOMEM);
+            ctx->write_buffer_size = FFMIN(2 * ctx->write_buffer_size, INT_MAX / 8);
+            goto reallocate_and_try_again;
+        }
+        // Write failed for some other reason.
+        return ret;
+    }
+
+    // Overflow but we didn't notice.
+    av_assert0(put_bits_count(&pbc) <= 8 * ctx->write_buffer_size);
+
+    if (put_bits_count(&pbc) % 8)
+        unit->data_bit_padding = 8 - put_bits_count(&pbc) % 8;
+    else
+        unit->data_bit_padding = 0;
+
+    flush_put_bits(&pbc);
+
+    ret = ff_cbs_alloc_unit_data(ctx, unit, put_bits_count(&pbc) / 8);
+    if (ret < 0)
+        return ret;
+
+    memcpy(unit->data, ctx->write_buffer, unit->data_size);
+
+    return 0;
+}
+
+int ff_cbs_write_fragment_data(CodedBitstreamContext *ctx,
+                               CodedBitstreamFragment *frag)
+{
+    int err, i;
+
+    for (i = 0; i < frag->nb_units; i++) {
+        CodedBitstreamUnit *unit = &frag->units[i];
+
+        if (!unit->content)
+            continue;
+
+        av_buffer_unref(&unit->data_ref);
+        unit->data = NULL;
+
+        err = cbs_write_unit_data(ctx, unit);
+        if (err < 0) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Failed to write unit %d "
+                   "(type %"PRIu32").\n", i, unit->type);
+            return err;
+        }
+        av_assert0(unit->data && unit->data_ref);
+    }
+
+    av_buffer_unref(&frag->data_ref);
+    frag->data = NULL;
+
+    err = ctx->codec->assemble_fragment(ctx, frag);
+    if (err < 0) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Failed to assemble fragment.\n");
+        return err;
+    }
+    av_assert0(frag->data && frag->data_ref);
+
+    return 0;
+}
+
+int ff_cbs_write_extradata(CodedBitstreamContext *ctx,
+                           AVCodecParameters *par,
+                           CodedBitstreamFragment *frag)
+{
+    int err;
+
+    err = ff_cbs_write_fragment_data(ctx, frag);
+    if (err < 0)
+        return err;
+
+    av_freep(&par->extradata);
+
+    par->extradata = av_malloc(frag->data_size +
+                               AV_INPUT_BUFFER_PADDING_SIZE);
+    if (!par->extradata)
+        return AVERROR(ENOMEM);
+
+    memcpy(par->extradata, frag->data, frag->data_size);
+    memset(par->extradata + frag->data_size, 0,
+           AV_INPUT_BUFFER_PADDING_SIZE);
+    par->extradata_size = frag->data_size;
+
+    return 0;
+}
+
+int ff_cbs_write_packet(CodedBitstreamContext *ctx,
+                        AVPacket *pkt,
+                        CodedBitstreamFragment *frag)
+{
+    AVBufferRef *buf;
+    int err;
+
+    err = ff_cbs_write_fragment_data(ctx, frag);
+    if (err < 0)
+        return err;
+
+    buf = av_buffer_ref(frag->data_ref);
+    if (!buf)
+        return AVERROR(ENOMEM);
+
+    av_buffer_unref(&pkt->buf);
+
+    pkt->buf  = buf;
+    pkt->data = frag->data;
+    pkt->size = frag->data_size;
+
+    return 0;
+}
+
+
+void ff_cbs_trace_header(CodedBitstreamContext *ctx,
+                         const char *name)
+{
+    if (!ctx->trace_enable)
+        return;
+
+    av_log(ctx->log_ctx, ctx->trace_level, "%s\n", name);
+}
+
+void ff_cbs_trace_syntax_element(CodedBitstreamContext *ctx, int position,
+                                 const char *str, const int *subscripts,
+                                 const char *bits, int64_t value)
+{
+    char name[256];
+    size_t name_len, bits_len;
+    int pad, subs, i, j, k, n;
+
+    if (!ctx->trace_enable)
+        return;
+
+    av_assert0(value >= INT_MIN && value <= UINT32_MAX);
+
+    subs = subscripts ? subscripts[0] : 0;
+    n = 0;
+    for (i = j = 0; str[i];) {
+        if (str[i] == '[') {
+            if (n < subs) {
+                ++n;
+                k = snprintf(name + j, sizeof(name) - j, "[%d", subscripts[n]);
+                av_assert0(k > 0 && j + k < sizeof(name));
+                j += k;
+                for (++i; str[i] && str[i] != ']'; i++);
+                av_assert0(str[i] == ']');
+            } else {
+                while (str[i] && str[i] != ']')
+                    name[j++] = str[i++];
+                av_assert0(str[i] == ']');
+            }
+        } else {
+            av_assert0(j + 1 < sizeof(name));
+            name[j++] = str[i++];
+        }
+    }
+    av_assert0(j + 1 < sizeof(name));
+    name[j] = 0;
+    av_assert0(n == subs);
+
+    name_len = strlen(name);
+    bits_len = strlen(bits);
+
+    if (name_len + bits_len > 60)
+        pad = bits_len + 2;
+    else
+        pad = 61 - name_len;
+
+    av_log(ctx->log_ctx, ctx->trace_level, "%-10d  %s%*s = %"PRId64"\n",
+           position, name, pad, bits, value);
+}
+
+int ff_cbs_read_unsigned(CodedBitstreamContext *ctx, GetBitContext *gbc,
+                         int width, const char *name,
+                         const int *subscripts, uint32_t *write_to,
+                         uint32_t range_min, uint32_t range_max)
+{
+    uint32_t value;
+    int position;
+
+    av_assert0(width > 0 && width <= 32);
+
+    if (get_bits_left(gbc) < width) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid value at "
+               "%s: bitstream ended.\n", name);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (ctx->trace_enable)
+        position = get_bits_count(gbc);
+
+    value = get_bits_long(gbc, width);
+
+    if (ctx->trace_enable) {
+        char bits[33];
+        int i;
+        for (i = 0; i < width; i++)
+            bits[i] = value >> (width - i - 1) & 1 ? '1' : '0';
+        bits[i] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, position, name, subscripts,
+                                    bits, value);
+    }
+
+    if (value < range_min || value > range_max) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
+               "%"PRIu32", but must be in [%"PRIu32",%"PRIu32"].\n",
+               name, value, range_min, range_max);
+        return AVERROR_INVALIDDATA;
+    }
+
+    *write_to = value;
+    return 0;
+}
+
+int ff_cbs_write_unsigned(CodedBitstreamContext *ctx, PutBitContext *pbc,
+                          int width, const char *name,
+                          const int *subscripts, uint32_t value,
+                          uint32_t range_min, uint32_t range_max)
+{
+    av_assert0(width > 0 && width <= 32);
+
+    if (value < range_min || value > range_max) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
+               "%"PRIu32", but must be in [%"PRIu32",%"PRIu32"].\n",
+               name, value, range_min, range_max);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (put_bits_left(pbc) < width)
+        return AVERROR(ENOSPC);
+
+    if (ctx->trace_enable) {
+        char bits[33];
+        int i;
+        for (i = 0; i < width; i++)
+            bits[i] = value >> (width - i - 1) & 1 ? '1' : '0';
+        bits[i] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, put_bits_count(pbc),
+                                    name, subscripts, bits, value);
+    }
+
+    if (width < 32)
+        put_bits(pbc, width, value);
+    else
+        put_bits32(pbc, value);
+
+    return 0;
+}
+
+int ff_cbs_read_signed(CodedBitstreamContext *ctx, GetBitContext *gbc,
+                       int width, const char *name,
+                       const int *subscripts, int32_t *write_to,
+                       int32_t range_min, int32_t range_max)
+{
+    int32_t value;
+    int position;
+
+    av_assert0(width > 0 && width <= 32);
+
+    if (get_bits_left(gbc) < width) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid value at "
+               "%s: bitstream ended.\n", name);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (ctx->trace_enable)
+        position = get_bits_count(gbc);
+
+    value = get_sbits_long(gbc, width);
+
+    if (ctx->trace_enable) {
+        char bits[33];
+        int i;
+        for (i = 0; i < width; i++)
+            bits[i] = value & (1U << (width - i - 1)) ? '1' : '0';
+        bits[i] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, position, name, subscripts,
+                                    bits, value);
+    }
+
+    if (value < range_min || value > range_max) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
+               "%"PRId32", but must be in [%"PRId32",%"PRId32"].\n",
+               name, value, range_min, range_max);
+        return AVERROR_INVALIDDATA;
+    }
+
+    *write_to = value;
+    return 0;
+}
+
+int ff_cbs_write_signed(CodedBitstreamContext *ctx, PutBitContext *pbc,
+                        int width, const char *name,
+                        const int *subscripts, int32_t value,
+                        int32_t range_min, int32_t range_max)
+{
+    av_assert0(width > 0 && width <= 32);
+
+    if (value < range_min || value > range_max) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
+               "%"PRId32", but must be in [%"PRId32",%"PRId32"].\n",
+               name, value, range_min, range_max);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (put_bits_left(pbc) < width)
+        return AVERROR(ENOSPC);
+
+    if (ctx->trace_enable) {
+        char bits[33];
+        int i;
+        for (i = 0; i < width; i++)
+            bits[i] = value & (1U << (width - i - 1)) ? '1' : '0';
+        bits[i] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, put_bits_count(pbc),
+                                    name, subscripts, bits, value);
+    }
+
+    if (width < 32)
+        put_sbits(pbc, width, value);
+    else
+        put_bits32(pbc, value);
+
+    return 0;
+}
+
+
+int ff_cbs_alloc_unit_content(CodedBitstreamContext *ctx,
+                              CodedBitstreamUnit *unit,
+                              size_t size,
+                              void (*free)(void *opaque, uint8_t *data))
+{
+    av_assert0(!unit->content && !unit->content_ref);
+
+    unit->content = av_mallocz(size);
+    if (!unit->content)
+        return AVERROR(ENOMEM);
+
+    unit->content_ref = av_buffer_create(unit->content, size,
+                                         free, NULL, 0);
+    if (!unit->content_ref) {
+        av_freep(&unit->content);
+        return AVERROR(ENOMEM);
+    }
+
+    return 0;
+}
+
+int ff_cbs_alloc_unit_data(CodedBitstreamContext *ctx,
+                           CodedBitstreamUnit *unit,
+                           size_t size)
+{
+    av_assert0(!unit->data && !unit->data_ref);
+
+    unit->data_ref = av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
+    if (!unit->data_ref)
+        return AVERROR(ENOMEM);
+
+    unit->data      = unit->data_ref->data;
+    unit->data_size = size;
+
+    memset(unit->data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
+
+    return 0;
+}
+
+static int cbs_insert_unit(CodedBitstreamContext *ctx,
+                           CodedBitstreamFragment *frag,
+                           int position)
+{
+    CodedBitstreamUnit *units;
+
+    if (frag->nb_units < frag->nb_units_allocated) {
+        units = frag->units;
+
+        if (position < frag->nb_units)
+            memmove(units + position + 1, units + position,
+                    (frag->nb_units - position) * sizeof(*units));
+    } else {
+        units = av_malloc_array(frag->nb_units*2 + 1, sizeof(*units));
+        if (!units)
+            return AVERROR(ENOMEM);
+
+        frag->nb_units_allocated = 2*frag->nb_units_allocated + 1;
+
+        if (position > 0)
+            memcpy(units, frag->units, position * sizeof(*units));
+
+        if (position < frag->nb_units)
+            memcpy(units + position + 1, frag->units + position,
+                   (frag->nb_units - position) * sizeof(*units));
+    }
+
+    memset(units + position, 0, sizeof(*units));
+
+    if (units != frag->units) {
+        av_free(frag->units);
+        frag->units = units;
+    }
+
+    ++frag->nb_units;
+
+    return 0;
+}
+
+int ff_cbs_insert_unit_content(CodedBitstreamContext *ctx,
+                               CodedBitstreamFragment *frag,
+                               int position,
+                               CodedBitstreamUnitType type,
+                               void *content,
+                               AVBufferRef *content_buf)
+{
+    CodedBitstreamUnit *unit;
+    AVBufferRef *content_ref;
+    int err;
+
+    if (position == -1)
+        position = frag->nb_units;
+    av_assert0(position >= 0 && position <= frag->nb_units);
+
+    if (content_buf) {
+        content_ref = av_buffer_ref(content_buf);
+        if (!content_ref)
+            return AVERROR(ENOMEM);
+    } else {
+        content_ref = NULL;
+    }
+
+    err = cbs_insert_unit(ctx, frag, position);
+    if (err < 0) {
+        av_buffer_unref(&content_ref);
+        return err;
+    }
+
+    unit = &frag->units[position];
+    unit->type        = type;
+    unit->content     = content;
+    unit->content_ref = content_ref;
+
+    return 0;
+}
+
+int ff_cbs_insert_unit_data(CodedBitstreamContext *ctx,
+                            CodedBitstreamFragment *frag,
+                            int position,
+                            CodedBitstreamUnitType type,
+                            uint8_t *data, size_t data_size,
+                            AVBufferRef *data_buf)
+{
+    CodedBitstreamUnit *unit;
+    AVBufferRef *data_ref;
+    int err;
+
+    if (position == -1)
+        position = frag->nb_units;
+    av_assert0(position >= 0 && position <= frag->nb_units);
+
+    if (data_buf)
+        data_ref = av_buffer_ref(data_buf);
+    else
+        data_ref = av_buffer_create(data, data_size, NULL, NULL, 0);
+    if (!data_ref) {
+        if (!data_buf)
+            av_free(data);
+        return AVERROR(ENOMEM);
+    }
+
+    err = cbs_insert_unit(ctx, frag, position);
+    if (err < 0) {
+        av_buffer_unref(&data_ref);
+        return err;
+    }
+
+    unit = &frag->units[position];
+    unit->type      = type;
+    unit->data      = data;
+    unit->data_size = data_size;
+    unit->data_ref  = data_ref;
+
+    return 0;
+}
+
+void ff_cbs_delete_unit(CodedBitstreamContext *ctx,
+                        CodedBitstreamFragment *frag,
+                        int position)
+{
+    av_assert0(0 <= position && position < frag->nb_units
+                             && "Unit to be deleted not in fragment.");
+
+    cbs_unit_uninit(ctx, &frag->units[position]);
+
+    --frag->nb_units;
+
+    if (frag->nb_units > 0)
+        memmove(frag->units + position,
+                frag->units + position + 1,
+                (frag->nb_units - position) * sizeof(*frag->units));
+}