Quantcast Kona LHi dropping frames from VCR with TBC? - digitalFAQ Forum
  #1  
06-22-2018, 12:15 PM
ryan42 ryan42 is offline
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Hello. I am trying to convert some VHS tapes that were made from clips of home movies with the following setup:

- AJA Kona LHi
- JVC HR-S7900U VCR

Some of the clips capture fine, and others will drop hundreds of frames during capture. With the JVC's TBC turned off the drop rate is much worse, but with the TBC turned on, some clips that still look fine on a CRT monitor still won't usefully capture.

I thought perhaps I needed an external TBC so I picked up a Prime Image TBC/Freeze II. I don't seem to get much of a difference in dropped frames with this TBC in the signal path, but I can see the hue/setup controls making a difference in the picture so I know it is doing something.

Where should I go from here to try to get a better capture?
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  #2  
06-22-2018, 01:45 PM
Judd_the_budd Judd_the_budd is offline
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Following along.

Couple questions:

Vhs tape speed? SP?
Wiring diagram? S-video? Composite?
PC? Mac? Capture Software? Capture format?
Operating system?

Thx! Looking forward to solutions, as I am building similar system.
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  #3  
06-22-2018, 06:57 PM
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lordsmurf lordsmurf is offline
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The old rack-mount TBCs (Prime Image, etc) are not made for VHS, and may do nothing. This is known. However, an external frame sync TBC is needed to prevent dropped frames (purify the signal). The lin TBC in the VCR does not do that, and is only for visual improvements. Not the signal.

Dropped frames is almost always either
(1) no TBC, or
(2) I/O errors, meaning hard drive or SSD. You usually need a dedicated capture drive,
(3) bad capture settings, including bad codec choice

Process of elimination says verify the settings, or try another card, or another TBC, or dedicated capture drive, and see if any fixes it.

Which codec are you using for capture? If you need another capture card or TBC, PM me about it. I have some extra gear.

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06-23-2018, 01:53 AM
ryan42 ryan42 is offline
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Quote:
Originally Posted by Judd_the_budd View Post
Following along.

Couple questions:

Vhs tape speed? SP?
Wiring diagram? S-video? Composite?
PC? Mac? Capture Software? Capture format?
Operating system?

Thx! Looking forward to solutions, as I am building similar system.
The problematic tape I'm working on now is SP. The VCR is hooked by S-Video to the Y/C input on the Prime Image TBC. The Y/C output of the TBC is connected to the Kona's Y/C input.

I'm using a 2008 Mac Pro, 8-core 3.0 GHz, 24 GB RAM, Mac OS 10.11.6, and recording to a RAID-0 of two SSDs. The SSDs are old and it is only SATA-II but it can still push 450 MB/s sustained write. It's my old workhorse but it should be up to the task of recording SD video, I hope. I'm just using the AJA Control Center software, writing MOV files, 10-bit YUV. I'm not sure if the codec is the best choice but I'm still in the testing phase of this setup so I haven't played with those settings much.

I don't suspect the computer is the problem, because this tape has a bunch of camcorder clips on it and I can get through 45 minutes with only a few dropped frames, then a clip will come on that starts dropping by the dozens. The next clip can go back to dropping no frames. If it were a computer issue, I'd expect dropped frames throughout the recording. I've also been able to capture a less-problematic tape without issue, but this is the second tape on my stack.

Quote:
Originally Posted by lordsmurf View Post
The old rack-mount TBCs (Prime Image, etc) are not made for VHS, and may do nothing. This is known. However, an external frame sync TBC is needed to prevent dropped frames (purify the signal). The lin TBC in the VCR does not do that, and is only for visual improvements. Not the signal.

Dropped frames is almost always either
(1) no TBC, or
(2) I/O errors, meaning hard drive or SSD. You usually need a dedicated capture drive,
(3) bad capture settings, including bad codec choice

Process of elimination says verify the settings, or try another card, or another TBC, or dedicated capture drive, and see if any fixes it.

Which codec are you using for capture? If you need another capture card or TBC, PM me about it. I have some extra gear.
Ah that would figure. I'm leaning towards TBC for the reasons listed above, and it sounds like I picked a bad TBC for this application. I should have asked first, but this was less than the AV Toolbox model and seemed worth a try. It sounds like I should have sprung for the AVT. I'll PM you.
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  #5  
06-23-2018, 09:07 AM
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lordsmurf lordsmurf is offline
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Quote:
Originally Posted by ryan42 View Post
it sounds like I picked a bad TBC for this application. I should have asked first, but this was less than the AV Toolbox model and seemed worth a try. It sounds like I should have sprung for the AVT.
That's exactly it. Most of those low-priced TBCs are not worth anything at all. It's broadcaster gear from the 80s and 90s, created for pristine non-consumer sources. Not VHS, Video8/Hi8, etc. The wrong toll for the task. A few of those ancient boxes can work with some sources, but more often it will not. The size of that gear alone, not to mention the sharp edges, make them highly unappealing as well.

The black AVT-8710 units all have defective chips, don't bother. Ghosting and frame sticking problems, as described here: Is my new AVT-8710 DOA? (screenshots/clips of error)

That leaves the desired DataVideo and Cypress/AVT units from the sweet spot era of the late 90s and 2000s. And those almost always cost more than the defective boxes, or the broadcast junkers.

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  #6  
06-24-2018, 10:48 PM
VideoTechMan VideoTechMan is offline
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Quote:
Originally Posted by ryan42 View Post
The problematic tape I'm working on now is SP. The VCR is hooked by S-Video to the Y/C input on the Prime Image TBC. The Y/C output of the TBC is connected to the Kona's Y/C input.

I'm using a 2008 Mac Pro, 8-core 3.0 GHz, 24 GB RAM, Mac OS 10.11.6, and recording to a RAID-0 of two SSDs. The SSDs are old and it is only SATA-II but it can still push 450 MB/s sustained write. It's my old workhorse but it should be up to the task of recording SD video, I hope. I'm just using the AJA Control Center software, writing MOV files, 10-bit YUV. I'm not sure if the codec is the best choice but I'm still in the testing phase of this setup so I haven't played with those settings much.
Don't capture in 10-bit YUV, use 8-bit....all analog based sources are 8-bit. In addition, capturing in 10-bit is more I/O intense and is mostly for HD based workflows. I also have the Kona LHi and I have captured in DV50 and uncompressed and never dropped any frames. It sounds like you are also capturing YUV which is uncompressed, that will use tons of hard drive space. I would recommend DV50 instead, which captures in 4:2:2 colorspace.

Plus as LS mentioned, getting a proper external full-frame TBC will help with the signal stabilization. I use the Leitch DPS-575, though its rackmount it so far has worked well for my VHS based captures (the ones I have tested) using the Panasonic AG-5710.

VTM
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  #7  
06-25-2018, 03:27 PM
ryan42 ryan42 is offline
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Thanks for the advice everyone. I've managed to capture many other tapes in my stack without much issue, so I'm only down to one tape that is giving me problems, and only for a few minutes of that tape in total. Unless I come across more tapes that need extra help I think I can call this one solved. Indeed the Prime Image TBC doesn't make a flip of difference. The JVC's TBC definitely does help, but it has its limitations. On most of the tapes I have, the JVC's TBC allows me to capture with zero dropped frames –*with it off, I get noticeable frame loss.

I have changed my capture settings as recommended by VideoTechMan and while it isn't making a difference in frame loss on the problematic clips, it sure does create more manageable files!
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