VSE - Improper audio on frame 1 when exporting to lossy-compressed audio #68945
Short description of error
When audio from the vse is exported to lossy-compressed formats (mp3, ac3, aac), blender is adding an odd fadein on it. (see channel 6 in the attached blender screenshot).
It actually appears somewhat like a fadein in blender, but when imported into audacity, there is a .005 second silence, then instantly full volume.
Whats worse, this false fadein seems to override any keyframes on the first frame: if the audio has a 6 frame fade in keyframed in, it will do that weirdness for the first frame, then return to the proper volume for frame 2 and continue the fade in. This creates a kind of 'hump' where there should be a smooth transition. (See channel 3 in the attached blender screenshot)
Oddly, this bug does not happen on non-lossy formats (wav, pcm, flac) (see channels 4 and 7 on the attached blender screenshot).
Exact steps for others to reproduce the error
Load an audio file with audio immediately at the beginning into the vse
Add a fadein
Render audio out to a lossy compressed format (either in a video, or as audio alone)
Can I add that the preview playback in the viewport doesn't exhibit this problem. It only manifests in the encoded output file. I'm not sure how far back this goes but I can confirm this has been a problem in 2.8 for several weeks now.
ok, this is weird... today im not getting the same issue with the 'bump' when exporting only audio, even compressed.... but I still see the issue every time when exporting to video/audio combined... but I now see it with ANY audio codec in video, not just lossy formats.
I do experience similar issues during preview, but not in rendered files, at least not "audibly"
This is quite contrary, to what's reported.
I never looked at cause of this issue, but I am pretty sure it's outside of scope of VSE code.
This seemed like a headscratcher, until I realized, that this has nothing to do with animating the strip.
here is reproducible sample:
What happens is:
If sound strip has volume greater than 0, first few ms of rendered audio looks like fade-in from volume 0 to 1, then it fades to volume of the strip itself. This happens during first frame.
This is happens even with lossless format, unlike original report.
@neXyon can you please look into this? I have looked at what values we are setting, and that all seems to be correct.
This issue was referenced by
If I'm right this issue is the same as #52472 and it was my mistake that I didn't correctly backport this to upstream audaspace and this caused a reintroduction of the bug. Please check if it's fixed for you now! There is some more explanation in the other bug report.
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