Help restoring poor quality source tape

[Traderbam]

I've been capturing this tape (Huffyuv AVI) which seems to be in poor condition. It is likely poor exposure settings on the old camcorder that recorded directly to VHS tape in the mid 90s as other parts of the tape seem better. It seems to get worse when deinterlacing and converting to ProRes so I can import into Resolve. I couldn't make anything decent of it with Resolve colour tools.

I'm a beginner on this, but any recommendations on what tools/scripts to use to salvage some of this please?

[lollo]

Difficult.

Before diving into big stuff like DaVinci, you may want to explore basic commands like ColorYUV(off_y=-50, gain_y=50), just as example.

Whas is clipped in the whites cannot be recovered, but you can somehow obtain a "better" look.

[Traderbam]

Difficult.

Before diving into big stuff like DaVinci, you may want to explore basic commands like ColorYUV(off_y=-50, gain_y=50), just as example.

Whas is clipped in the whites cannot be recovered, but you can somehow obtain a "better" look.


[Attachment 85637 - Click to enlarge]


[Attachment 85638 - Click to enlarge]

That does improve things a bit. I guess I can fix the tint etc. in Resolve.

I assume that the Auto functions like AutoLevels isn't any use here since we are starting from a 'bad' range to begin with? I had thought of adjusting something in the procamp during capture but not sure if this will make any difference if the exposure is already bad on source tape.

[lollo]

I assume that the Auto functions like AutoLevels isn't any use here since we are starting from a 'bad' range to begin with?

Maybe, you can experiment all the "auto" functions in the filter.

I had thought of adjusting something in the procamp during capture but not sure if this will make any difference if the exposure is already bad on source tape.

The procamp tuning is used to stay in the capturable range of the card, to avoid crushing the blacks and clipping the whites. It does not help with problems baked in the source, nor does AviSynth if the values are out of range.

In any case, any adjustement should be done in post processing, use the procamp just for its main purpose.

[aramkolt]

If it is a fist generation tape, there's a fair chance that capturing with an analog proc amp prior to the capture card could bring the levels down before digitization and avoid most (and possibly all clipping) if this is a first generation (original) tape. If it is copy of the original, then yeah, the clipping is probably baked in. Some say that the digital proc amp settings within something like virtual dub aren't as good as using a real analog proc amp, but I haven't really come across a tape this bad to say that for sure. If you've already gotten the best capture you can, you could send me one of the tapes and I'll verify and send it back to you for just the cost of return shipping after posting what I can do. I'd only suggest doing that if you're in the USA though, just higher potential for it to get lost in the mail if shipped from elsewhere.

[Traderbam]

If it is a fist generation tape, there's a fair chance that capturing with an analog proc amp prior to the capture card could bring the levels down before digitization and avoid most (and possibly all clipping) if this is a first generation (original) tape. If it is copy of the original, then yeah, the clipping is probably baked in. Some say that the digital proc amp settings within something like virtual dub aren't as good as using a real analog proc amp, but I haven't really come across a tape this bad to say that for sure. If you've already gotten the best capture you can, you could send me one of the tapes and I'll verify and send it back to you for just the cost of return shipping after posting what I can do. I'd only suggest doing that if you're in the USA though, just higher potential for it to get lost in the mail if shipped from elsewhere.

Hi, it is a first generation tape. I have a DVK-100 which is a lightweight TBC which has some colour processing modes. I've never used them but that might be a better shout than trying the procamp settings in VDub? I would need to dig out the manual and have a play around but it's probably not a solid solution.

[Alwyn]

IMO, getting the levels as best you can before capture is a must. ColorYUV improves it so it must be able to be captured with better levels.

Check/use the VDub histogram, in conjunction with the procamp controls, prior to capture.

And the DVK-100, if it's the same as the -200, is a fantastic procamp because you don't need to fiddle around with your mouse and the digital sliders of your digitiser; you've got a great big knob to twiddle back and forth to get the levels just right.

Normal rules apply: Brightness for the left edge, Contrast for the right.

This is how I've got mine set up:


[Attachment 85644 - Click to enlarge]

[Sharc]

.... Some say that the digital proc amp settings within something like virtual dub aren't as good as using a real analog proc amp, but I haven't really come across a tape this bad to say that for sure. ...

When the signal is already clipped at the analog input of the capture device one cannot fix it after A/D conversion on the digital side with "digital proc-amp" adjustments. It would only shift the clipped signal up/down. It cannot digitally "unclip" the signal.

[Traderbam]

.... Some say that the digital proc amp settings within something like virtual dub aren't as good as using a real analog proc amp, but I haven't really come across a tape this bad to say that for sure. ...

When the signal is already clipped at the analog input of the capture device one cannot fix it after A/D conversion on the digital side with "digital proc-amp" adjustments. It would only shift the clipped signal up/down. It cannot digitally "unclip" the signal.

Yes, I've noticed this when using the levels in VDub, adjusting the brightness/contrast just slides the signal left/right. I'll try with the DVK100 (thanks Alwyn) and report back.

Any download to having the DVK-100 in line before my TBC given that the DVK has some sort of TBC capability itself although I don't think this works on every output socket.

[Alwyn]

I've noticed this when using the levels in VDub, adjusting the brightness/contrast just slides the signal left/right.

Not so. Have a look at my guide on using the Histogram here.

Any download to having the DVK-100 in line before my TBC given that the DVK has some sort of TBC capability itself although I don't think this works on every output socket

.
Good question, I've always considered the DVK to be the frame TBC so it goes after the Line TBC (all over my head, I just do what I'm told). If you have a real TBC, I couldn't say what order; try a quick capture both ways.

[Traderbam]

I did have the histogram looking more like your screenshots but it didn't seem to take effect on the resulting capture. That was using the "levels" option in VDub. Adjusting on the capture filters option for the device settings also didn't seem to make any odds. I might need to explore the Graph option.

[Sharc]

@Traderbam: You are probably wasting your time when trying to "fix" clipped video by means of digital "proc amp" tinkering. Put your external analog proc-amp into service and see whether you can adjust the signal to a linear (unclipped) analog waveform. Depends where the clipping took place along your workflow.
Does it look the same when you connect your VCR directly to the TV? What model is your capture device (AGC issues?). I'd assume it shouldn't clip hard (?) at y=234 (screenshot) but should go somewhat into the >235 luma range, which would mean the clipping happens earlier in the workflow in which case it can't be solved with the digital "proc-amp"......


[Attachment 85652 - Click to enlarge]

[lordsmurf]

Good question, I've always considered the DVK to be the frame TBC so it goes after the Line TBC (all over my head, I just do what I'm told). If you have a real TBC, I couldn't say what order; try a quick capture both ways.

In most cases, it's: VCR/camera (with line TBC) > frame TBC > proc amp

So in this case, you'd ignore the fact that the DVK has a weak frame TBC, and simply use it as a proc amp.

ALSO NOTE: Sometimes VCRs, and line TBCs, can cause luma issues you see here. So try other VCRs, with/without line TBC. Sometimes strip out all TBCs, to see if this is being induced anywhere. Same for using a different capture card. Don't just assume the tape is bad without thorough testing. This does not mean TBCs/VCRs are bad, but rather you ran into a bad interaction. That happens. Just multi-test to be sure, before deciding that the tape is bad.

[Traderbam]

Update: Using DVK100 as a procamp definitely helps. Annoyingly I cannot seem to preview in VDub while viewing histogram - I need to switch between preview and overlay to get it to work (maybe a limitation of the USB-Live2 card?)

When tweaking with proc-amp is it recommended to reduce the brightness as much as possible and bring the gain up in post-processing, or reduce by the minimum needed to get something workable for post?

Here's a few samples - this is with the brightness control on DVK as low as it goes.

[Sharc]

Hmmm, better, but darks clipped/crushed at Y=16 and brights too low at Y~180 (grayish picture)
Maybe in post try something like

levels(0,1.2,210,0,255,coring=false)

[Attachment 85656 - Click to enlarge]

[Sharc]

I did have the histogram looking more like your screenshots but it didn't seem to take effect on the resulting capture. That was using the "levels" option in VDub. Adjusting on the capture filters option for the device settings also didn't seem to make any odds. I might need to explore the Graph option.

Take a look here:
https://forum.videohelp.com/threads/417310-Capturing-S-vhs-tapes-using-VirtualDub-corr...e2#post2765007

Edit:
Script for the player (MPC-HC in my case):

DirectShowSource("GV-USB2.grf",audio=false,framecount=15000) 
converttoYV16(interlaced=true) #convert to planar

## uncomment one of the 4 options below as needed:
Histogram("levels")     # Histogram on the side
#Histogram("classic")   # vertical Waveform Monitor on the side
#TurnRight().Histogram("classic").TurnLeft()   # horizontal Waveform Monitor at the top of the frame
#Histogram("color2")    #Vectorscope

ConvertToRGB32(matrix="rec601")

[Alwyn]

Annoyingly I cannot seem to preview in VDub while viewing histogram - I need to switch between preview and overlay to get it to work (maybe a limitation of the USB-Live2 card?)

No, it appears to be an issue with VDub 1.9.11. The GV-USB2 won't display the Histo and Preview together in 1.9.11, but VDub2 does. Since we're not allowed to capture with VDub 2 I set the Histogram/levels with it and then capture with...

Anyway, at least you can control the histogram using the DVK with the tape running in 1.9.11.

When tweaking with proc-amp is it recommended to reduce the brightness as much as possible and bring the gain up in post-processing, or reduce by the minimum needed to get something workable for post?

I'd be setting them (B and C) correctly, so the histogram is within limits for capture and make fine adjustments in Post.