To my ffmpeg brethren: I'm trying to share some fun content with the world, specifically an off-air feed from France 2 (which has the Olympics, bcast in UHD, 50 fps, main 10, full-on BT2020 with PQ HDR, at ~18 mbits composite TS rate), and am absolutely confounded. Hoping that someone here knows how fMP4 a/v interleaving and sync is supposed to work.
Find the live fMP4 HLS here: https://endpnt.com/hls/france2uhd/france2uhd.m3u8 When playing this HLS on iOS or macOS Safari, we get: frame re-ordering (ie. "jumps") at what appear to be approximately fMP4 chunk boundaries, audio is several seconds behind, despite audio and video quickly decoding and playing upon starting the stream. Playing the same in VLC, we start decoding frames immediately after downloading the first few chunks, but no audio will play until several seconds have elapsed - so, no a/v sync here. However, no inter-fragment frame reordering/jumps between fragments. Using MPV and ffplay, *things work* - a/v is sync'd, and doesn't drift when playing the stream for arbitrarily long durations. If I switch from fMP4 chunks to good ol' TS chunks, everything but Safari plays just fine - a/v sync intact, etc. Of course, we know AAPL will never support HEVC in .TS chunks, so I'd like to use fMP4. In examining the mp4 init and the other mp4 segments produced by ffmpeg (tried 4.3.7-old, 6.0.1, 7.0, 7.1, and git-current via JVS's "static ffmpeg" builds on several different linux distributions), everything looks kosher. We get the right ATOMs where expected (AFAICT), we are told about frame durations in the codec, and the decoder can plainly see how many samples are in each EAC3 packet as muxed in the mp4 fragments. Things I've tried in adjusting the input/output of ffmpeg, which have not resolved/changed anything regarding this "a/v desync on some players but not all" issue: -copyts, -reset_timestamps 1, -use_wallclock_as_timestamps, -async, -fps_mode drop, -r 50, -re, etc. -transcoding audio to aac, regular ac3, and mp3 (also at 44.1k rate vs. the bcast source of 48khz) -different segment lengths -ss n (which doesn't do anything, as the stream is not seekable) -fflags +nobuffer and various exhaustive combinations of -experimental low latency options -max_muxing_queue_size 9999 -max_interleave_delta 0 and other muxer-tweaks -manually rewriting audio timestamps with setpts into the future (seems to not carry over into fMP4, does seem to work in TS, but we don't want that) Here's what's being ran, and what one could use to replicate this problem on their system (assuming you have access and can sustain 18 mbits from my .ts relay server, running icecast-kh): ffmpeg -icy 0 -i http://endpnt.com:8000/france-2-uhd.ts -vcodec copy -acodec copy -tag:v hvc1 -b:v 18M -map 0:i:3021 -map 0:i:3032 -hls_segment_type fmp4 -hls_init_time 4 -hls_list_size 10 -hls_time 4 -hls_flags iframes_only+independent_segments+delete_segments france2uhd.m3u8 No useful "errors" (other than normal AC3 implied vs. explicit sample lengths) or cli output from ffmpeg exist here, as there's nothing to report. I've included the last bit of input detection, fmp4 stuff firing up, and then a little runtime output after this note in case anyone is curious. Clues welcome & appreciated. Best, -Tk [hevc @ 0x55f6ac243700] Error parsing NAL unit #2. [hevc @ 0x55f6ac243700] PPS id out of range: 0 Last message repeated 1 times [hevc @ 0x55f6ac243700] Error parsing NAL unit #2. [hevc @ 0x55f6ac243700] PPS id out of range: 0 Last message repeated 1 times [hevc @ 0x55f6ac243700] Error parsing NAL unit #2. [hevc @ 0x55f6ac243700] PPS id out of range: 0 Last message repeated 1 times [hevc @ 0x55f6ac243700] Error parsing NAL unit #2. [hevc @ 0x55f6ac243700] PPS id out of range: 0 Last message repeated 1 times [hevc @ 0x55f6ac243700] Error parsing NAL unit #2. Input #0, mpegts, from 'http://endpnt.com:8000/france-2-uhd.ts': Duration: N/A, start: 41795.243156, bitrate: N/A Program 2305 Stream #0:0[0xbcd]: Video: hevc (Main 10) ([36][0][0][0] / 0x0024), yuv420p10le(tv, bt2020nc/bt2020/smpte2084), 3840x2160 [SAR 1:1 DAR 16:9], 50 fps, 50 tbr, 90k tbn, 50 tbc Stream #0:1[0xbce]: Data: bin_data (AC-4 / 0x342D4341) Stream #0:2[0xbd8](fre): Audio: eac3 ([6][0][0][0] / 0x0006), 48000 Hz, stereo, fltp, 128 kb/s Stream #0:3[0xbd9](qaa): Audio: eac3 ([6][0][0][0] / 0x0006), 48000 Hz, stereo, fltp, 128 kb/s Stream #0:4[0xbda](fre): Audio: eac3 ([6][0][0][0] / 0x0006), 48000 Hz, stereo, fltp, 128 kb/s (visual impaired) (descriptions) Stream #0:5[0xbdb](fre): Subtitle: dvb_subtitle ([6][0][0][0] / 0x0006) (hearing impaired) Stream #0:6[0xbdc](fre): Subtitle: dvb_subtitle ([6][0][0][0] / 0x0006) [hls @ 0x55f6ac2cae00] Opening 'init.mp4' for writing [mp4 @ 0x55f6ac227a80] track 1: codec frame size is not set Output #0, hls, to 'france2uhd.m3u8': Metadata: encoder : Lavf58.45.100 Stream #0:0: Video: hevc (Main 10) (hvc1 / 0x31637668), yuv420p10le(tv, bt2020nc/bt2020/smpte2084), 3840x2160 [SAR 1:1 DAR 16:9], q=2-31, 18000 kb/s, 50 fps, 50 tbr, 12800 tbn, 50 tbc Stream #0:1(fre): Audio: eac3 ([6][0][0][0] / 0x0006), 48000 Hz, stereo, fltp, 128 kb/s Stream mapping: Stream #0:0 -> #0:0 (copy) Stream #0:2 -> #0:1 (copy) Press [q] to stop, [?] for help [hls @ 0x55f6ac2cae00] Opening 'france2uhd0.m4s' for writing=N/A speed=2.11x [hls @ 0x55f6ac2cae00] Opening 'france2uhd.m3u8.tmp' for writing [hls @ 0x55f6ac2cae00] Opening 'france2uhd1.m4s' for writing=N/A speed=1.55x [hls @ 0x55f6ac2cae00] Opening 'france2uhd.m3u8.tmp' for writing [hls @ 0x55f6ac2cae00] Opening 'france2uhd2.m4s' for writing=N/A speed=1.34x [hls @ 0x55f6ac2cae00] Opening 'france2uhd.m3u8.tmp' for writing frame= 737 fps= 55 q=-1.0 size=N/A time=00:00:16.70 bitrate=N/A speed=1.25x _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
