VHS capture - 'audio is lagging at max audio buffering. Restarting source audio.'

[scartout]

Welcome all,

I've just completed capturing my VHS tapes into computer using OBS and RCA USB Capture Card (named here 'Urządzenie do przechwytywania wideo') and I'm planning to capture some new tapes soon, so I need your help. For 4 of 10 tapes, not the worst one I have, I've encontered two problems:

1. Initial problem, which is causing audio and video to lose sync, is losing sync more and more as long as it hit the limit - 'adding 960 milliseconds of audio buffering, total audio buffering is now 960 milliseconds (source: Urządzenie do przechwytywania wideo)'
2. Finally, audio mutes - 'Source Urządzenie do przechwytywania wideo audio is lagging (over by 2536.72 ms) at max audio buffering. Restarting source audio.'

Problem have place only in certain moments of the tape, but is not caused by tracking/flickering. Sometimes this is the place where one recording stops and another one starts but there is no rule (maybe moment of no audio?). When capturing, I hear a voice is in sync, so looks like this is not the problem with the Capture Card. OBS is adding a buffer which cause audio and video to lose sync, and finally is hitting the limit so audio is completly lost.

My CPU works less than 2% (i5-11400H), graphic is RTX 3050 Ti. I made sure antivirus (Avast) and other unnecessary programs are not working. I'm doing nothing during the capturing process. Also I changed the priority of OBS to high in task manager, and I was restarting OBS before starting each recording (each recording has about 2h). I read various solutions on the forum but no progress.

My output is FPS 29.97, Bitrate 3500, H264 (mp4) 720x576, ACC 48000 kHz.

I'm attaching example logs. Also I perfomed the analysis: https://obsproject.com/tools/analyzer?log_url=https://obsproject.com/logs/aJ3eKX5MP60hDWOj#logURL

I want to assure that problems won't back before next capturing session. Is there a way to avoid them?

 

[AaronD]

No matter what's going on, try to not have any Critical problems. So disable HAGS.

The audio problem itself could be with the Mismatched Sample Rates. Does it also sound sped up or slowed down, with an associated pitch change? Even if not, OBS doesn't resample very well, so you really need to have everything match.

My output is FPS 29.97, Bitrate 3500, H264 (mp4) 720x576, ACC 48000 kHz.

Your *output* is that, but your input is 44100:

19:16:35.850: [DShow Device: 'Urządzenie do przechwytywania wideo'] settings updated:
19:16:35.850:     video device: USB Video
19:16:35.850:     video path: \\?\usb#vid_534d&pid_0021&mi_00#6&20689590&0&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\global
19:16:35.850:     resolution: 720x576
19:16:35.850:     flip: 0
19:16:35.850:     fps: 25.00 (interval: 400000)
19:16:35.850:     format: YUY2
19:16:35.850:     buffering: disabled
19:16:35.850:     hardware decode: disabled
19:16:35.864:     using video device audio: no
19:16:35.864:     separate audio filter
19:16:35.864:     sample rate: 44100
19:16:35.864:     channels: 2
19:16:35.864:     audio type: Capture

There's the mismatch. Change one of them to match, plus the Critical fix, and see where you are.

 

[scartout]

Thanks for the response.

19:16:35.850: [DShow Device: 'Urządzenie do przechwytywania wideo'] settings updated:
19:16:35.850:     video device: USB Video
19:16:35.850:     video path: \\?\usb#vid_534d&pid_0021&mi_00#6&20689590&0&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\global
19:16:35.850:     resolution: 720x576
19:16:35.850:     flip: 0
19:16:35.850:     fps: 25.00 (interval: 400000)
19:16:35.850:     format: YUY2
19:16:35.850:     buffering: disabled
19:16:35.850:     hardware decode: disabled
19:16:35.864:     using video device audio: no
19:16:35.864:     separate audio filter
19:16:35.864:     sample rate: 44100
19:16:35.864:     channels: 2
19:16:35.864:     audio type: Capture

Above ones are default settings of USB capturing device, so I adjusted a little for tests now.

What I've tried:
- removed all critical issues (HAGS disabled)
- starts OBS as admin
- tried USB 25 fps/output 25 fps, USB 29.97 fps/output 29.97 fps, USB 30 fps/output 30 fps (generally, tapes recorded in PAL 25)
- changed output to 44100, however, OBS Anylyzer says 96000 is for the USB Card and this cannot be changed to lower in Windows settings, so I've tried 44100 and 48000 as output

Please check the newest analyze, example is for 29.97 fps non admin https://obsproject.com/tools/analyzer?log_url=https://obsproject.com/logs/g67AHSAQVXWRcWiD#entry_1

Unfortunately, nothing helped. OBS starts adding miliseconds in the same moment of the tape so audio loses sync. But to reproduce this I need to record the first 25 mins - if I just start before the faulty moment, no issue.

 

[AaronD]

(generally, tapes recorded in PAL 25)

Try to match the original source as much as possible. If the tape is 25fps interlaced, then set OBS to 25, or to 50 with a 2x deinterlacer. If you have a tape that is different, change the settings to match.

OBS Anylyzer says 96000 is for the USB Card and this cannot be changed to lower in Windows settings

That's weird. You don't need better than 44.1k for anything, and 48k is the professional standard outside of CD's and their influence. Anything beyond that requires more data for no audible benefit, so I'm surprised that an analog video capture card can't slow down to the basic standard. Are you sure you've looked *everywhere*?

Or do you mean your mic:

12:11:39.645: [win-wasapi: 'Mikrofon/Wejście liniowe'] update settings:
12:11:39.645:     device id: {0.0.1.00000000}.{2df8f053-99d9-4d49-872e-9dbc48cbec89}
12:11:39.645:     use device timing: 0
12:11:39.646: [Loaded global audio device]: 'Mikrofon/Wejście liniowe'
12:11:39.665: WASAPI: Device 'Mikrofon (USB Audio)' [96000 Hz] initialized (source: Mikrofon/Wejście liniowe)

Those are more likely to be stuck at a higher rate, more for "non-technical audiophool" reasons than for anything else.
If you don't use the mic, delete it or Disable it. Don't keep stuff around that can only hurt. Likewise for anything else you don't use.

OBS starts adding miliseconds in the same moment of the tape so audio loses sync. But to reproduce this I need to record the first 25 mins - if I just start before the faulty moment, no issue.

What happens if you record 20 minutes at a time, back up the tape a little bit, and start a new recording? Then put the sections back together in a video editor?

It's not as nice as doing the whole thing in one shot, but if it works...

---

There's been a longstanding issue with OBS's Monitor losing sync and gradually falling behind...and behind...and behind...seemingly without limit. The cause seems like a network-streaming mentality from whoever wrote the bit that talks to the hardware buffer. In that mindset, it doesn't matter if it's a minute behind, as long as it's smooth, so any hiccup simply expands the buffer until the missing data that finally arrives has a place to slot in before it's needed. But that completely wrecks something that needs to stay in sync with something else, live right here and now!

When the hardware has a different clock from the rest of the system (some does, some doesn't), even the same nominal setting is slightly different. That difference eventually guarantees that a naive simple buffer of *any* size, will eventually fill up or run out. And the network-stream mentality expands the buffer again.

If that's the underlying problem, then the solution is to use different hardware - roll the dice again, whether it has its own internal clock or uses the system clock - or to connect OBS to a virtual thing that necessarily does use the same clock, and then connect that virtual thing to the actual hardware. Move the problem somewhere else, so the somewhere else can handle it correctly.