Issues capturing 8mm tape - Terrible FPS in Vdub

[ccisbeast]

I'm attempting to transfer some old 8mm tapes using a couple different methods.

Originally we had been using a program called "Ulead Video Studio" that came free with my Sabrent USB-AVCPT USB 2.0 capture card. It did well enough, but I can't quite tell if it's dropping any frames, and it seems that it might be. I thought capturing directly to Lagarith Lossless might make things move a bit smoother, but instead it produced a weird effect every so often where the top half of the screen was not sync'd with the bottom, resulting in choppy image or a visible line in the center of the picture. So I figured it would be a good idea to ditch Ulead entirely.

So, now I'm trying to capture to an external HDD, capturing directly to the HDD using Virtual Dub using Lagarith Lossless compression and do all steps at once. (Capture, compress, transfer to external). However, in VirtualDub, my FPS is consistently around 20, and I can't get it any higher, whether compressed or uncompressed, with or without video playback on the screen, even before I begin capture it says 20 FPS in the bottom right corner. When recording, it drops about 30% of all frames and the audio is heavily desynchronized. I've looked for solutions but have been unable to find any.

So, my two questions then,

1. Am I right to pursue Vdub for capturing? I understand it's pretty much the best freeware there is; or is there merit in using Ulead? (other than being unable to get Vdub to work)
2. If so, what do you recommend to remedy my FPS woes? I don't think it's my harddrive, it's a brand new 7200 RPM 2TB Seagate, and it's definitely not my CPU. I have an i7 2600 threaded to 8 cores, and I disabled nearly every service that wasn't required for A/V, system stability, and internet (though I do not connect to the internet until I have to). CPU usage doesn't go above 3% according to Vdub.

I suspect it is my cheapo capture device, as I understand Vdub is picky about capture chipsets, but should it really cause such a fierce dip in FPS considering the specifications of the rest of my system?

What's your take, Videohelp? And many thanks in advance!

[Brad]

Hoo boy.

What kind of external HDD? If it's anything but eSATA you're asking for trouble.

If you unplug the HDD, is the bottom-right corner number still limited to 20 fps?

[ccisbeast]

Well, it's USB 3.0, but I thought USB 3.0 transfer rate would be enough to capture compressed data. (Doesn't the bus speed far exceed the HDD write speed anyway? I thought hardly any devices could max out most bus speeds, maybe I'm just thinking of PCIe)

Either way, unplugging the expansion drive did not help, unfortunately. Frame rate holds around 18-22. If it matter at all, during preview, the frames will play, then stop, then play again, but it seems as if you can see all of the "dropped" frames played in super-speed when it displays the next 20 or so correct frames. It's not an exact start-stop-start, more like start for 20 frames, stop, fast forward through whatever other frames, then start again. Not sure if that means anything, I'm no expert.

[Brad]

My understanding is that USB 3.0 still uses a shared bus. Maybe I'm wrong or maybe it isn't a problem.

Obviously you need to get the capture device to function properly before anything else.

[ccisbeast]

How can I tell if the capture device is functioning properly? Or is the low FPS an obvious symptom of a poor capture chipset? I am putting my finger on the capture device as the suspect, considering it cost me like 10 bucks.

[Brad]

I don't think there is a way to really be sure. I assume you have tried plugging it into multiple USB ports. Can you try another computer?

[jagabo]

Turn off audio playback (in VirtualDub) while capturing and previewing. Don't compress the audio while capturing (leave it uncompressed PCM, many audio codecs are single threaded and slow). Fiddle with the different sync options in Capture -> Timing... especially "Do not resync..." Make sure multithreading is enabled in Lagarith. Make sure you have selected the right frame rate: 29.97.

[ccisbeast]

Many thanks! Audio playback was indeed the issue - I turned it off and my FPS instantly jumped to 30-31! I had heard that video playback could cause issues, but had never known that audio playback as well could cause issues.

So, now two minor questions you've raised for me...

1. You said the frame rate should be 29.97. Why not 59.97? (either way, I set it to either of those and the FPS still hover between 30 and 31)
2. Should I resync audio/video as opposed to selecting "Do not resync"? It sounds like it will prevent any desync, and since allowing it to resync is not affecting my FPS, it sounds like it would be beneficial, yes?

Once again, many many thanks! My capturing has been delayed a whole week trying to rectify this issue!

[ccisbeast]

Another side question, can you pre-set an end time for a capture in VDub, or a capture length?

[jagabo]

1. You said the frame rate should be 29.97. Why not 59.97? (either way, I set it to either of those and the FPS still hover between 30 and 31)

NTSC video is always 59.94 fields per second, save as 29.97 frames per second.

2. Should I resync audio/video as opposed to selecting "Do not resync"? It sounds like it will prevent any desync, and since allowing it to resync is not affecting my FPS, it sounds like it would be beneficial, yes?

Try it both ways. See if the audio is still in sync after an hour or two of continuous recording. Use whichever works.

can you pre-set an end time for a capture in VDub

Capture -> Stop Conditions... Capture Time Exceeds [x] seconds.