The Matter of VirtualDub Out of Sync Audio

[Avagadro1]

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[nicholasserra]

Direct stream copy is just an output setting telling VDub to not re-encode when exporting your clip. Doesn't have anything to do with your capture.

You're doing a pretty big roundabout to fix a badly captured video. Should focus more on getting the original capture working correctly. I guess i'm one of the lucky few who have never had a audio sync issue in vdub.

Couple things to check:
- What vdub version are you using? 32 or 64 bit? Smurf swears by not using vdub 2, only capture with vdub 1. Might want to try both 32 and 64 bit versions of it.
- What card are you using for capture? You said a Hap and a cheapo chinese? Do you have capture sync issues with both these cards?
- What's the signal chain? VCR > Capture > USB in? Just checking to see if anything else might be screwing you up.
- What's your PC hardware? Is your hard drive fast enough to capture this correctly? Have a SSD? Enough RAM?
- What video codec are you capturing to? Are you capturing raw PCM audio, and do you have the right format set for it (48k, stereo, 16bit normally)

[Alwyn]

All you have to do is sync your audio (as you have done) then put both the video and audio to Direct Stream Copy, then Save As AVI. Virtual Dub will re-multiplex (ie combine) your video and audio streams with the audio offset you have put in, without actually re-encoding/re-rendering your streams. All you are in effect doing is shuffling the audio along a bit; the relative position of the video and audio streams is in the file data. There is no need to do a complete re-render ie no need for "Full Processing".

Full processing mode is only needed when you have actually done something to the video (or audio) such as add a filter, a crop or changing the save as format (say MP4).

I'd try doing this is Premiere Elements; you might be able to ungroup the audio from the video then set up an offset (I don't use Premiere).

[jagabo]

To clarify:

Video -> Direct Stream Copy in VirtualDub copies the input video to the output file without even decompressing it. No filtering is performed by VirtualDub. This mode is good for re-multiplexing into a new file. You can specify a new audio delay to fix audio sync problems (only when audio is off by a constant amount over the entire video). But if you're planning to filter and re-encode your video with VirtualDub there's no reason to remux first. You can just use the same audio delay when you save your filtered video.

Full processing mode is required if you plan to use any filters. The video is decompressed and the filter chain enabled. Long ago the video was always converted to RGB before filtering. But for the last several years video may or may not be converted to RGB depending on what filters are used.

In Fast Recompress mode the source video is decompressed but the filter chain isn't enabled. The decompressed video is passed directly to the output codec in whatever color format the decompresser output. Typically YUY2 or YV12.

In Normal Recompress mode the source video is decompressed and converted to RGB. The filter chain is not enabled. The RGB is then sent to the output codec.

Note that some of these settings might not work depending on the source container and which source filter is used to read it.

[Avagadro1]

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[Alwyn]

I’m guessing that I should have both video and audio Direct Stream Copy selected DURING CAPTURE. Then change to Full Processing Mode for applying any of VirtualDub’s filters.

Full processing or Direct Stream Copy does not apply when you are capturing (and cannot be set when in "Capture AVI..." mode). They only apply when you are "processing" the captured video.

Since many users of VirtualDub experience the out-of-sync audio problem

This may not be the case. I have never had a sync problem. There may be many out there that do not have a problem; you only hear from people who have a problem.

[Avagadro1]

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[anachronon]

I have had the same problem with VirtualDub. I don't know if the problem is with VirtualDub, or my capture device. That said, I have used the "Audio>Interleaving>Audio skew correction>Delay audio track by . . ." to fix this. I also leave both Video and Audio set to "Direct Stream Copy". There is no need to reprocess.

I suspect that the problem comes from the "Audio/Video Interleave Options" (the same dialog box as "Audio Skew Correction"). Above Audio Skew is a line, "Preload _____ ms of audio before video starts" The default setting of this is "500". I don't know what this does, as attempting to change it has caused VirtualDub to behave strangely. It just seems awfully coincidental, that setting the skew to "-500" solves the sync problem in video copies.

[DB83]

^^ Those settings >> interleave/preload << only affect playback. Nothing to do with capture. Think of it like with streaming buffering. As you stream you do not playback instantly but a small section of video/audio that has been loaded in to memory and as that then plays another section is loaded. If the buffer is empty then you experience a delay.


The part of capturing in vdub that controls audio sync in from capture >> timing menu. There are several settings but I leave mine at default. The moral is only mess with these if you know what you are doing.


But there are many factors that control whether sync is maintained. The quality of your capture device. The OS. Capturing to the same drive as your OS. The vcr/cabling. Even the actual tape. The list is endless. Or rather the situation will vary from one user to the next.

[Avagadro1]

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[DB83]

Your understanding is correct. Sorry if I did not make it clear enough. So you have eliminated one potential issue.

[Avagadro1]

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[lingyi]

lordsmurf as stated many times lack of audio sync is because of dropped frames due to the lack of a proper frame external TBC. The TBC in the VCR or an ES10/ES5 isn't enough to stop dropped frames.

"Audio drift is almost always caused by dropped frames.
Video frames drop, audio frames do not.

Do you have an external framesync TBC in the hardware chain.workflow? If not, there's your problem."

https://forum.videohelp.com/threads/386291-Captured-Video-with-Audio-Drift

https://www.videohelp.com/search?q=lordsmurf+audio+drift&siteurl=&Search=Search

Before you, but...but...think about it. It makes logical sense!

[Avagadro1]

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[lingyi]

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"Updated Feb 2021

Available:

NTSC only
- early BV10, essentially green AVT-8710 + DataVideo TBC-100 performance (excellent!), $1895 - my last TBC!"

http://www.digitalfaq.com/forum/marketplace/8243-sale-tbc-1000-a.html

Edit: For those who are screaming...HOW MUCH!!!??? Understand that lordsmurf and the trustworthy regulars who resell their gear are prices at or near market price for known/proven quality equipment. They may not have paid that much when they originally got it, but if they sell it significantly below current market price, someone would likely buy it just to resell. Potentially taking an opportunity away from someone who wants to use for their project.