Anyway to boost contrast without clipping?

[Master Tape]

After capturing a few VHS tapes in VirtualDub and correcting the levels in the proc-amp to prevent clipping, the picture seems a bit dull and lifeless. The contrast is at 106, so whites look a bit grey. If i try to boost the contrast in post, it then just clips the whites. Is there anyway to boost the contrast without clipping, or even through overlay/mask?

[Sharc]

Post a sample of your non-clipped capture.
(In my experience it is normally better to reduce the proc-amp contrast setting a few notches for capturing, and do the rest in post processing, but it depends on the capture setup of course).
Use avisynth's histogram() as an indicator how to tweak your capture. Maybe the black is too elevated?

[Master Tape]

Here's two examples, one where i find the white background to be very dull and another a live action clip showing the sky in the background. It looks better when you play the original tape on tv of course.

I can make it look a little better by increasing the contrast to as far as i can in Avisynth right to the edge of the line on the histogram, but it just still seems like it could be better, i find the colours a bit washed out.

[jagabo]

Something like this?

ColorYUV(gain_y=50, off_y=-8, cont_u=50, cont_v=50)

[Sharc]

This^, or it's perhaps more intuitive to work with brightness, contrast, saturation.
Also some denoising would do no harm.

AVISource("Clip 2.avi")
converttoYV16(interlaced=true)
SmoothTweak(brightness=-8,contrast=1.2,saturation=1.3)
SMDegrain(tr=3,thSAD=1000,interlaced=true) #denoise interlaced aware
histogram() #for debugging only
ConvertToYV12(interlaced=true) #for x264 encoding

[Master Tape]

Thanks, looks much better now. I've had to reduce the contrast in certain parts of the full video as there was some clipping, so i suppose it'll be a scene by scene basis.

The denoiser made all the difference too. Is it best to use it before deinterlacing? I did try using NeatVideo the other day but i find it too aggressive, it removes detail which isn't noise like fine detail such as stitching in a jumper.

[Sharc]

The denoiser made all the difference too. Is it best to use it before deinterlacing?

Most noise filters are designed for progressive video. Therefore you should apply these filters after (bob-)deinterlacing, or - as an alternative - on even/odd grouped separated fields.
Those filters which can be used on interlaced video may have a boolean variable 'interlaced' in their settings. SMDegrain(....., interlaced=true) is one of these.
There are plenty of posts about this subject how to use spatial/temporal-spatial filters on interlaced video. In short, the safe way is to deinterlace before filtering (and re-interlace at the end if you want the final format interlaced).