[FFmpeg-devel] [PATCH 1/2] avcodec/h264_ps: Check for truncation at fixed_frame_rate_flag

[Carl Eugen Hoyos]

Am Mo., 16. Dez. 2019 um 01:00 Uhr schrieb James Almer <jamrial at gmail.com>:
>
> On 12/15/2019 8:50 PM, Carl Eugen Hoyos wrote:
> > Am So., 15. Dez. 2019 um 23:25 Uhr schrieb James Almer <jamrial at gmail.com>:
> >>
> >> On 12/15/2019 7:00 PM, Michael Niedermayer wrote:
> >>> Fixes: Ticket7249 (No longer displaying a scary red message)
> >>>
> >>> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> >>> ---
> >>>  libavcodec/h264_ps.c | 4 ++++
> >>>  1 file changed, 4 insertions(+)
> >>>
> >>> diff --git a/libavcodec/h264_ps.c b/libavcodec/h264_ps.c
> >>> index e8738d8502..74f12f8979 100644
> >>> --- a/libavcodec/h264_ps.c
> >>> +++ b/libavcodec/h264_ps.c
> >>> @@ -203,6 +203,10 @@ static inline int decode_vui_parameters(GetBitContext *gb, AVCodecContext *avctx
> >>>              sps->num_units_in_tick = num_units_in_tick;
> >>>              sps->time_scale = time_scale;
> >>>          }
> >>> +        if (get_bits_left(gb) == 0) {
> >>
> >> Doing this check here sounds like it's tailored specifically for the
> >> sample in the ticket. What if another file is truncated one bit after
> >> this point? Or one bit before? You will get the scary red message for
> >> it. Will you also add a check for it?
> >> We can't clutter this file with new get_bits_left() checks every time a
> >> user shares their broken samples with us just to get a less scary output
> >> in their terminals.
> >
> > Do you know of another proprietary or open-source encoder that encodes
> > streams with such a truncation?
>
> There was an old hevc encoder that did something like that. We ended up
> adding a workaround for it as well.

> And i can imagine capturing a
> transport stream with bad network conditions could result in all kinds
> randomly placed truncation.

I don't think a "random" truncation as produced by reception or
network issues can lead to similar messages as in the ticket.

Carl Eugen