Re: [FFmpeg-devel] The log level of "co located POCs unavailable" should not be ERROR
On Sun, 3 Mar 2019 at 00:41, Michael Niedermayer wrote: > If the frame is copied, its copy would be at a different point in > time so it may need a different poc and simply copying it might > cause issues Sorry I didn't state it clearly. What I meant is POC = previous POC + 2, not copied [1]. This is correct, since the frame is missing you don't have better choices. I just wonder why not set field_poc? If I add these two lines: h->short_ref[0]->field_poc[0] = prev->field_poc[0] + 2; h->short_ref[0]->field_poc[1] = prev->field_poc[1] + 2; I find the error message is gone (only test videos that use frame coding throughout). [1]: https://github.com/FFmpeg/FFmpeg/blob/n4.1.1/libavcodec/h264_slice.c#L1599) ___ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
Re: [FFmpeg-devel] The log level of "co located POCs unavailable" should not be ERROR
On Fri, 1 Mar 2019 at 05:30, Michael Niedermayer wrote: > When data is missing (in live streaming or otherwise) it under > almost all cases cannot be losslessly recovered. So this use matches > the definition Yes, this is reasonable. But then "Frame num gap" should be of ERROR level too. H.264 standard states if there is a frame num gap, the decoder should infer an unintentional loss of pictures, assuming gaps_in_frame_num_value_allowed_flag = 0. But it is possible that FFmpeg encounters a frame loss but does not print any error messages, because the error concealment procedure (https://github.com/FFmpeg/FFmpeg/blob/n4.1.1/libavcodec/h264_slice.c#L1577) will clone the previous frame in place of the missing one. Also, regarding to the error concealment, why isn't `short_ref[0].field_poc` copied for cloned frames? The unset field_poc causes "co located POCs unavailable" error, despite `ref_list[1][0].poc` is valid when doing spatial direct predition. ___ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
[FFmpeg-devel] The log level of "co located POCs unavailable" should not be ERROR
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). ___ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
