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Old 05-31-2020, 05:34 AM   #1
bFooz
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Default Video import synchronisation bug

PROBLEM: Imported video files seem to be off sync. This is observed through the waveform.

Here I am using video file source.mp4 in 23.976fps. Steps I have done:

1) import source.mp4 into Reaper.



2) export this as a WAV into source_through_reaper.wav

3) import both source.mp4 and source_through_reaper.wav into Premiere Pro and observe the difference. Time selection is one frame in length.



I expect Premiere Pro as a dedicated video editor to behave properly when importing video files.

EDIT: After further attempts to synchronise properly, I have found sometimes video files sound earlier and sometimes later.
Bellow in red is a wav file created in Premiere Pro from a video file. In blue is the same video file imported directly into Reaper. The difference here is around 60ms.


Last edited by bFooz; 06-01-2020 at 04:04 AM.
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Old 09-29-2020, 07:22 AM   #2
nottooloud
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I have also seen this, with one addition. As I zoom in and out, I can sometimes see one of the waveforms shifting left and right relative to the other. Something is completely out of whack in the waveform display. Mac and Windows.
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Old 09-29-2020, 04:29 PM   #3
Meo-Ada Mespotine
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Do you have a sample-videofile, which can be tested by the devs?
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Old 10-02-2020, 10:11 AM   #4
nottooloud
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Try turning off Hi Res Peaks on the video. It appears to be a rendering issue with lossy formats.

https://forum.cockos.com/showthread.php?t=216904

although this may not be the same as your issue.
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Old 10-03-2020, 12:22 AM   #5
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I believe this is an issue caused by the audio in the mp4 being AAC (I am assuming it's not PCM). I have seen this issue for years in Cubase/Nuendo Pro Tools and Reaper. Basically when importing a video file that contains a lossy compressed audio format, the audio in many cases ends up running early due to the conversion like how you have discovered.

The way I get around this is I always ask the editor I'm working with to output the video file with PCM audio (essentially a wav file 48K 16bit or 24bit). Since the audio in the video isn't compressed, when you import it into a DAW it remains perfectly in synch and will line up with any supplied stems or OMF/AAF.

I also always render my video files with PCM audio when supplying them for mix previews etc as it means that if someone imports the video into something it will remain in synch.
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