Hello, I have a process that remuxes short HLS playlists into an mp4 format. The output mp4 in this process has an all black first frame when played back in either Safari or Quicktime Player. Everywhere else, the first frame does not have this black frame.
The process is an internal tool that uses libav directly so it's hard to share the code, but I think I can reproduce via an ffmpeg command line invocation against a single TS segment, so I'm hoping to be able to solve the problem by understanding how to change the ffmpeg command. All the sample files can be found in this public Google Drive: https://drive.google.com/drive/folders/1L8T5T4l_GUzxRnhjH-ojnT6-44FQLQq1?usp=drive_link . bbb_2.ts is the second segment of Big Buck Bunny (sourced from this test stream: https://test-streams.mux.dev/x36xhzz/url_0/193039199_mp4_h264_aac_hd_7.m3u8). If you open this ts file in Quicktime player or Safari, the first frame is NOT black. bbb_2_remuxed.mp4 has been remuxed using the following command: "ffmpeg -i bbb_2.ts -c copy -f mp4 bbb_2_remuxed.mp4". If you open it up in Quicktime Player or Safari, the first frame IS black. I think I traced it down to an extra entry in the "elst" atom. If you probe this remuxed mp4 with trace level debugging on ("ffprobe -v trace bbb_2_remuxed.mp4") there's a short duration entry in the edit list of the video track. [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fd357104bc0] type:'elst' parent:'edts' sz: 40 8 40 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fd357104bc0] track[0].edit_count = 2 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fd357104bc0] duration=15 time=-1 rate=1.000000 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fd357104bc0] duration=10000 time=2999 rate=1.000000 According to the Quicktime file format docs, the parent of the "elst" atom is "edts" and it is optional, so I removed that atom using mp4edit in the Bento4 tool kit. This produced "bbb_2_remuxed_no_edts.mp4". If you open this file in Quicktime or Safari, the first frame is NOT black. bbb_2_transcoded.mp4 is a transcoded version using "ffmpeg -i bbb_2.ts -video_track_timescale 90K -movflags +faststart bbb_2_transcoded.mp4". If you open this file in Quicktime or Safari, the first frame is NOT black. If you inspect the atoms in this file, the video "elst" atom is still there, but it only has a single entry in the list. [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fe3ecf06040] type:'elst' parent:'edts' sz: 28 8 28 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fe3ecf06040] track[0].edit_count = 1 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fe3ecf06040] duration=10017 time=3000 rate=1.000000 So, ultimately I think the extra entry in the elst edit table is the cause of the issue. My question is whether it is possible to not have that happen via the ffmpeg/libav invocation, or whether this is a problem with the source material? Thanks, Sid _______________________________________________ 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".
