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IDProjectCategoryView StatusDate SubmittedLast Update
0002538KdenliveRenderingpublic2012-03-09 01:012012-03-12 21:57
Assigned To 
Platform64 bitOSGentoo LinuxOS Version2008.0
Product VersionRecent git 
Target VersionFixed in Version 
Summary0002538: Quicktime audio sync bug
DescriptionThis is a rather odd bug, and I'm not really sure what would cause it.

If I render a file to an mp4 file (h264/aac) and play it with anything based of libavcodec (vlc, mplayer, etc) it plays fine. If I play the same file with something Quicktime based, the audio sync is off. (No edits, just one source file dumped into the timeline, project settings set to match the source settings)

The part that makes it odd, is that if I encode the same source file, with the same settings, directly with ffmpeg, if playes in sync on both libavcodec and quicktime based players.

ffprobe shows the audio streams starting at timestamp 0 for both encoded mp4 files.
TagsNo tags attached.
Build/Install MethodManual build from Git
Attached Files

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-  Notes
FishB8 (reporter)
2012-03-11 02:32

I have further found that this problem is not specific to Quicktime. Even though I can get ffplay to play back the rendered files with audio sync, if I then re-encode the files with ffmpeg, the audio sync from the second encode is out of sync in the same manner as seen with Quicktime.

May not be related, but when encoding with ffmpeg I noticed this output from the terminal: "Switching to NI mode, due to poor interleaving"
FishB8 (reporter)
2012-03-11 05:03

I may have narrowed down the issue somewhat. The original sources are DNxHD / MOV files from and AVID system. If I pull them directly in, the sync in the editor is fine, but the sync in the rendering is off. However, if I first transcode the file to MJPEG / AVI file, the sync in the editor is slightly off, but the sync in the rendering is correct.
FishB8 (reporter)
2012-03-12 21:57

After some more testing, I think this is specific to DNxHD. Here's what I've been able to determine:

- libavcodec based players also have sync issues, contrary to what I originally reported. It's just that it isn't nearly as noticeable as in quicktime.

- This only seems to be an issue with DNxHD. Transcoding to MJPEG or ProRes before importing both worked great. However the sync in the editor is always off. Perhaps kdenlive was just tested with DNxHD content (since that's whats mostly available in the transcode menu) and as a result messed everything else up? The exports are in sync, but the playback in the editor is not. The exact opposite is true if I use the original DNxHD sources.

- Doing some searching I've found that ffmpeg's support for interlaced DNxHD files is poor and buggy. The source files I'm working with are 1080i. Perhaps that is creating problems as well. (however, it seems to be ok for the purpose to transcoding them to other formats)

- Issue History
Date Modified Username Field Change
2012-03-09 01:01 FishB8 New Issue
2012-03-11 02:32 FishB8 Note Added: 0007925
2012-03-11 05:03 FishB8 Note Added: 0007926
2012-03-12 21:57 FishB8 Note Added: 0007927

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