On 15/11/18 04:27, James Almer wrote:
> The ISOBMFF and Matroska specs allow the last OBU in a Sample/Block to have
> obu_has_size_field equal to 0.
>
> Signed-off-by: James Almer <jamr...@gmail.com>
> ---
> See https://0x0.st/sUsU.mp4
>
> It apparently can't be decoded with either aom or dav1d atm, but the latter
> should be able to soon.
> You can try remuxing it using the av1_metadata bsf after this patch while at
> it,
> since the code to write obu_size fields unconditionally is still in place, and
> that should make it decodable with either library.
I wonder whether there should be an option somewhere for omitting the last size
field when writing? It would save a few bytes on every TU when using any
container which already has sizes.
> For some reason cbs_av1_read_unit() is already able to handle OBUs with no
> obu_size field. It was only cbs_av1_split_fragment() bailing out with them.
That came from the annex B support, before we decided that AVPackets would
never contain annex B.
> libavcodec/cbs_av1.c | 16 ++++++----------
> 1 file changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c
> index ed5211be19..e02bc7027a 100644
> --- a/libavcodec/cbs_av1.c
> +++ b/libavcodec/cbs_av1.c
> @@ -788,13 +788,6 @@ static int cbs_av1_split_fragment(CodedBitstreamContext
> *ctx,
> if (err < 0)
> goto fail;
>
> - if (!header.obu_has_size_field) {
> - av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid OBU for raw "
> - "stream: size field must be present.\n");
> - err = AVERROR_INVALIDDATA;
> - goto fail;
> - }
> -
> if (get_bits_left(&gbc) < 8) {
> av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid OBU: fragment "
> "too short (%zu bytes).\n", size);
> @@ -802,9 +795,12 @@ static int cbs_av1_split_fragment(CodedBitstreamContext
> *ctx,
> goto fail;
> }
>
> - err = cbs_av1_read_leb128(ctx, &gbc, "obu_size", &obu_size);
> - if (err < 0)
> - goto fail;
> + if (header.obu_has_size_field) {
> + err = cbs_av1_read_leb128(ctx, &gbc, "obu_size", &obu_size);
> + if (err < 0)
> + goto fail;
> + } else
> + obu_size = size - 1 - header.obu_extension_flag;
>
> pos = get_bits_count(&gbc);
> av_assert0(pos % 8 == 0 && pos / 8 <= size);
>
LGTM.
Thanks,
- Mark
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