On Wed, Dec 11, 2019 at 10:38 PM James Almer <jamr...@gmail.com> wrote:
> On 12/11/2019 6:03 PM, Michael Niedermayer wrote: > > Its unclear if shortening these NAL units would have no effect on them > > > > Fixes: assertion failure > > Fixes: > 19286/clusterfuzz-testcase-minimized-ffmpeg_BSF_H264_REDUNDANT_PPS_fuzzer-5707990724509696 > > > > Found-by: continuous fuzzing process > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > > --- > > libavcodec/cbs_h2645.c | 9 +++++++-- > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c > > index 5f71d80584..b38b1d99ef 100644 > > --- a/libavcodec/cbs_h2645.c > > +++ b/libavcodec/cbs_h2645.c > > @@ -564,11 +564,16 @@ static int > cbs_h2645_fragment_add_nals(CodedBitstreamContext *ctx, > > const H2645NAL *nal = &packet->nals[i]; > > AVBufferRef *ref; > > size_t size = nal->size; > > + int shorten = 1; > > + > > + // Do not shorten reserved and unspecified NALs > > + if (ctx->codec->codec_id == AV_CODEC_ID_H264) { > > + shorten = nal->type > 0 && nal->type < 23; > > + } > > > > // Remove trailing zeroes. > > - while (size > 0 && nal->data[size - 1] == 0) > > + while (shorten && size > 0 && nal->data[size - 1] == 0) > > --size; > > - av_assert0(size > 0); > > So this is a NAL unit with a bunch of zero bytes? How did it go through > the filter in h2645_parse? It's supposed to skip any NAL like this. > > I guess it triggered this workaround: /* see commit 3566042a0 */ if (bytestream2_get_bytes_left(&bc) >= 4 && bytestream2_peek_be32(&bc) == 0x000001E0) skip_trailing_zeros = 0; If I am not mistaken, then all NAL units except one consisting solely of a single 0x00 (where the RBSP is empty) have to have a rbsp_stop_one_bit. So the only instance where stripping zeroes is not good is for such a 0x00 unit. And such a unit should be stripped, because it actually can't be represented in annex b (which we output) at all. - Andreas _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
