Linjie Fu:
> From: Linjie Fu <linjie.justin...@gmail.com>
>
> Container may support multiple sample descriptions in a single
> bitstream, like multiple stsd in mov, which introduces different
> sequence header(e.g.profile/bit_depth) in the middle of the bitstream.
>
> Update the extradata field in context parameter once packet with
> different extradata is got.
>
> Signed-off-by: Linjie Fu <linjie.justin...@gmail.com>
> ---
> libavcodec/hevc_mp4toannexb_bsf.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/libavcodec/hevc_mp4toannexb_bsf.c
> b/libavcodec/hevc_mp4toannexb_bsf.c
> index 790dfb0394..36a83d0c95 100644
> --- a/libavcodec/hevc_mp4toannexb_bsf.c
> +++ b/libavcodec/hevc_mp4toannexb_bsf.c
> @@ -125,6 +125,9 @@ static int hevc_mp4toannexb_filter(AVBSFContext *ctx,
> AVPacket *out)
> int got_irap = 0;
> int i, ret = 0;
>
> + uint8_t *extradata;
> + size_t extradata_size = 0;
> +
> ret = ff_bsf_get_packet(ctx, &in);
> if (ret < 0)
> return ret;
> @@ -135,6 +138,26 @@ static int hevc_mp4toannexb_filter(AVBSFContext *ctx,
> AVPacket *out)
> return 0;
> }
>
> + extradata = av_packet_get_side_data(in, AV_PKT_DATA_NEW_EXTRADATA,
> &extradata_size);
> + if (extradata && extradata_size &&
> + (ctx->par_in->extradata_size != extradata_size ||
> + memcmp(ctx->par_in->extradata, extradata, extradata_size))) {
> + av_log(ctx, AV_LOG_VERBOSE, "Update extradata, size = %zu\n",
> extradata_size);
We use SIZE_SPECIFIER instead of zu due to MSVC compatibility. I don't
know if we actually support MSVC versions that old any more, but it is
still used.
> + /* Update extradata */
> + av_freep(&ctx->par_in->extradata);
> + ctx->par_in->extradata_size = extradata_size;
> + ctx->par_in->extradata = av_mallocz(extradata_size +
> AV_INPUT_BUFFER_PADDING_SIZE);
> + if (!ctx->par_in->extradata)
> + return AVERROR(ENOMEM);
> + memcpy(ctx->par_in->extradata, extradata, extradata_size);
> + /* Reinit */
> + ret = hevc_extradata_to_annexb(ctx);
> + if (ret < 0)
> + return ret;
> + s->length_size = ret;
> + s->extradata_parsed = 1;
> + }
> +
> bytestream2_init(&gb, in->data, in->size);
>
> while (bytestream2_get_bytes_left(&gb)) {
>
1. This is an API violation: par_in is set by the user before
initializing the BSF, par_out is set by the BSF in init. After init,
both are immutable.
2. Instead you should make hevc_extradata_to_annexb() accept a buffer
with length field (or maybe even factor everything that
hevc_mp4toannexb_init() does out of it and make that function accept a
buffer and a length field; and another field to return the reformatted
extradata and its size).
3. Notice that you need to actually modify the packet's
AV_PKT_DATA_NEW_EXTRADATA side-data to make it Annex B. Otherwise the
output will be incorrect.
4. And in case this BSF actually inserts the extradata in-band, it would
need to retain an internal copy of this new extradata.
(Andriy Gelman once sent a good patch that never got applied that added
the correct extradata in-band even when there are in-band updates to the
extradata. I suggest you look at this patch if you want to tackle this
problem.)
- Andreas
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