[FFmpeg-devel] The log level of "co located POCs unavailable" should not be ERROR

Michael Niedermayer michael at niedermayer.cc
Thu Feb 28 23:30:24 EET 2019

On Thu, Feb 28, 2019 at 11:33:50AM +0800, Yukun Guo wrote:
> The error message "co located POCs unavailable" is reported when the
> co-located picture of an H.264 B frame is missing during spatial direct
> predition. It comes from this line:
> https://github.com/FFmpeg/FFmpeg/blob/n4.1.1/libavcodec/h264_direct.c#L156
> and was originally commited for solving an issue found by fuzzing:
> https://bugzilla.mozilla.org/show_bug.cgi?id=1230286.
> I think the condition is quite normal for live streaming, 1) when the
> player first connects to the streaming server, it may receive B frames
> whose reference frames have never been sent; 2) when the bandwidth is
> limited, the server purposely drops packets due to buffer overflow.
> IMHO the log level should be on par with "Frame num gap" (if
> `gaps_in_frame_num_value_allowed_flag` is false) and "no picture"
> (both are found in h264_slice.c and use DEBUG level).

 * Something went wrong and cannot losslessly be recovered.
 * However, not all future data is affected.
#define AV_LOG_ERROR    16

When data is missing (in live streaming or otherwise) it under almost all
cases cannot be losslessly recovered. So this use matches the definition

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Old school: Use the lowest level language in which you can solve the problem
New school: Use the highest level language in which the latest supercomputer
            can solve the problem without the user falling asleep waiting.
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