DV to VCD, does cropping make sense?

[shito]

O.K., try to follow me on this one: I´m capturing a movie from an old VHS-tape via ADVC-50 to DV. Since the movie has an 1:2.35 aspect ratio, I´m capturing the black bars, as well. Since the tape is pretty old, the supposedly black bars aren´t black at all, but have quite a bit of noise in them.
Now I want to convert my DV to MPEG1, using TMPGenc. The question is, would it make sense to crop the DV-file first (in VD, for example) to get rid of the not-so-black bars to have TMPGenc use all its encoding-power purely on the movie itself? I know, that TMPGEnc will have to encode bars into the file to keep the aspect ratio, but will the quality be better, if I let it put them there or if I provide them in my captured DV-file? Or does it even make any difference at all?
My guess would be, that TMPGenc puts pure black bars (as in video-signal=0) on the cropped picture and encodes those into the MPEG1-stream, which would give me pure black bars as a result, as well, right? Or does the encoding process introduce noise if there´s no motion at all (as would be in the black bars)?

Any comment is appreciated.

Greets
Konrad

[energy80s]

Just use the crop facility in TMPG itself. You will have to crop the top and bottom 120 odd lines and replace them with black bars. I do this all the time as even with commercial DVD's sometimes the black bars aren't pure black and you notice the difference between the 21:9 bar and the 16:9 bar if you encode to 4:3 letterbox.

[shito]

Damn, I didn´t even realize TMPGEnc had such an option. Thanks, energy! Do you use the clipping oder do you use the mask-funktion? Does it make a difference aspect-ratio-wise or quality-wise?

Greets
Konrad

[energy80s]

I normally make CVD type files. These are 352 x 576. My source is usually 720 x 576, so I clip 8 pixels from the left and right of the picture to give my 704 x 576 and then when that is re-sized down to CVD resolution it means that it is dropping every other vertical line. If I am masking the top and bottom of the screen, I always replace the cropped video with black bars to keep the aspect ratio correct at 352 x 576 (or 288 if its a VCD). The trick is to remember that both measurements should be multiples of 16.