On front-end I create stream with chrome.tabCapture.capture or navigator.mediaDevices.getDisplayMedia methods. Then send chunks generated by MediaRecorder to server. On the server I have FFMpeg command which decodes chunks into .mp4 file. This is the command:
ffmpeg -y -i - -preset veryfast -tune zerolatency -filter_complex [0:v]split=3[v1][v2][v3];[v1]scale=w=-2:h=1080,fps=30[v1out];[v2]scale=w=-2:h=720,fps=30[v2out];[v3]scale=w=-2:h=480,fps=30[v3out] -map [v1out] -maxrate:0 6M -bufsize:0 12M -keyint_min 100 -g 100 -map [v2out] -maxrate:1 3M -bufsize:1 6M -keyint_min 100 -g 100 -map [v3out] -maxrate:2 1.5M -bufsize:2 3M -keyint_min 100 -g 100 -c:v libx264 -map a:0 -c:a:0 aac -b:a:0 128k -ac 2 -map a:0 -c:a:1 aac -b:a:1 96k -map a:0 -c:a:2 aac -b:a:2 96k -f hls -hls_time 2 -hls_playlist_type vod -hls_flags independent_segments+temp_file -hls_segment_type fmp4 -hls_segment_filename ./output/ready/output_%v_%03d.m4s -var_stream_map v:0,a:0 v:1,a:1 v:2,a:2 -master_pl_name master.m3u8 ./output/ready/stream_%v.m3u8 -map 0:v:0 -map 0:a:0 -c:v copy -c:a aac ./output/download/video.mp4 -map 0:a:0 -ar 16000 -ac 1 -c:a pcm_s16le ./output/captions/audio.wav -loglevel info
During the process of decoding I have these errors in logs:
[extract_extradata @ 0x60000264b250] Invalid NAL unit 0, skipping.
[h264 @ 0x13ff04e60] Invalid NAL unit 0, skipping.
[h264 @ 0x13ff04e60] co located POCs unavailable
[h264 @ 0x13ff04e60] negative number of zero coeffs at 17 0
[h264 @ 0x13ff04e60] error while decoding MB 17 0
[h264 @ 0x13ff04e60] concealing 3388 DC, 3388 AC, 3388 MV errors in B frame
[h264 @ 0x13ff04e60] missing picture in access unit with size 24158
[h264 @ 0x13ff04e60] Invalid NAL unit 0, skipping.
[h264 @ 0x13ff04e60] data partitioning is not implemented. Update your FFmpeg version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.
[h264 @ 0x13ff04e60] If you want to help, upload a sample of this file to https://streams.videolan.org/upload/ and contact the ffmpeg-devel mailing list. ([email protected])
[h264 @ 0x13ff04e60] no frame!
[h264 @ 0x13ff04e60] Unknown SAR index: 18.
[h264 @ 0x13ff04e60] Invalid NAL unit 0, skipping.
[h264 @ 0x13ff04e60] Unknown SAR index: 18.
[h264 @ 0x13ff04e60] number of reference frames (2+4) exceeds max (5; probably corrupt input), discarding one
[h264 @ 0x13ff04e60] number of reference frames (3+3) exceeds max (5; probably corrupt input), discarding one
[h264 @ 0x13ff04e60] number of reference frames (4+2) exceeds max (5; probably corrupt input), discarding one
[h264 @ 0x13ff04e60] FMO is not implemented. Update your FFmpeg version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.
[h264 @ 0x13ff04e60] sps_id 4 out of range
This issue is very inconsistent and happen in rare cases (I can't understand the logic). Most of the time chunks decoded successfully, but sometimes not.
How to understand where the issue is coming from ? Is it possible for FFMpeg to skip wrong data and generate mp4 file anyway even with glitches, but don't crush ?