Doom9's Forum - View Single Post - VirtualDub2 cropped video fails to sync to audio with "match duration"

stormy1777 · 2nd November 2018, 09:22

Figured to open a separate thread instead of hitting the main one with possibly many folks watching

If not right, feel free to move to other main thread.

This is probably a very basic question:

Load a 10min video at 29.9 fps, and an audio clip that is 5 minutes, in the Frame Rate dialog it will offer to ~double the frame rate to "match duration" of video/audio..

Now, go ahead and CROP/TRIM the video anywhere, start/mid/end and remove 3-5 minutes, a large chunk.

The expectation is that it would "know" that video stream has FEWER frames, and ADJUST the "match duration" fps, but it does not, it keeps the original fps value, which cuts video way before the audio

A somewhat RELATED issue if you trim/crop the video from the *START*, then the audio becomes out of sync, my naive question, why can't the newly trimmed video simply be "numbered" with frame0.. last frame, why does it still "remember" the original non-cropped video and uses that as the audio-sync.

I know that SAVING The trimmed video and RELOADING it will do this, but that may be an hour video, so require a lot of time.

is there a possibility to make some changes in the management of "frame starting point" or "total frame count" and adjust it each time to the loaded audio? if that is a backward compatible issue, maybe offer a "new" way to trim/crop.. and of course, if user does an UNDO of a trim, then the frames would re-number again, and so on.

Thanks.
Stormy.

2nd November 2018, 09:22	#1 \| Link
stormy1777 Registered User Join Date: Jul 2002 Posts: 241	VirtualDub2 cropped video fails to sync to audio with "match duration" Figured to open a separate thread instead of hitting the main one with possibly many folks watching If not right, feel free to move to other main thread. This is probably a very basic question: Load a 10min video at 29.9 fps, and an audio clip that is 5 minutes, in the Frame Rate dialog it will offer to ~double the frame rate to "match duration" of video/audio.. Now, go ahead and CROP/TRIM the video anywhere, start/mid/end and remove 3-5 minutes, a large chunk. The expectation is that it would "know" that video stream has FEWER frames, and ADJUST the "match duration" fps, but it does not, it keeps the original fps value, which cuts video way before the audio A somewhat RELATED issue if you trim/crop the video from the START, then the audio becomes out of sync, my naive question, why can't the newly trimmed video simply be "numbered" with frame0.. last frame, why does it still "remember" the original non-cropped video and uses that as the audio-sync. I know that SAVING The trimmed video and RELOADING it will do this, but that may be an hour video, so require a lot of time. is there a possibility to make some changes in the management of "frame starting point" or "total frame count" and adjust it each time to the loaded audio? if that is a backward compatible issue, maybe offer a "new" way to trim/crop.. and of course, if user does an UNDO of a trim, then the frames would re-number again, and so on. Thanks. Stormy.