Using CLIP frame in TMPGEnc,what's going on?

[RWANDREWS]

I do not understand various aspects of the clip frame function in TMPGEnc. Can someone please explain them to me?

1) I use the CLIP frame to eliminate the noise on my VHS captures when encoding to MPEG-2. Is there a formula to keep the aspect ratio correct, top to bottom, left to right ? I always clip in multiples of 4. If I clip in odd proportions, does my final product look distorted?

2) Can clipping off ALL of the black bars in a LBX version save bit rate? I don't wish to change to full screen, just conserve bits for video.

3) What does the MASK function do exactly? Does using this increase or decrease bit rate required?

Thanking you in advance

[txpharoah]

Be sure the correct ARRANGE METHOD is selected.

[RWANDREWS]

TXPharoah,

Thanks for the tip, but I have yet another question. Aethetically speaking, which is best to use, full screen + keep aspect ratio, or center+keep aspect ? (Assuming a 4:3 vid)

[txpharoah]

Depends on the situation...

If you just want to cut off the noise on bottom (outside the viewing range of the tv), the center/aspect is best.

If the problem bleeds into the viewable area, then full/aspect. The only drawback here is you are now stretching the picture, and depending on the source quality, it may not be able to retain good quality after the encode. This is great for covering up tracking errors or funny colors at the top of the screen. Full/aspect clip is actually a hybrid clip/crop. It clips as best it can, but crops in order to main 4:3.

[C53248]

3) What does the MASK function do exactly? Does using this increase or decrease bit rate required?

MASK replaces the clipped area with a color, black by default. Without it, your image gets smaller, e.g. if you clip the bottom 12 lines from a 480-line video, it will be 468 lines tall instead of 480. If your output size were still set to 480, then those 468 lines would be redistributed over the 480. You should use MASK in this case. Those black lines won't show up on a normal TV, and they will keep you aspect ratio correct. Since pure clean black will compress better than anything, it won't take any real bitrate.

2) Can clipping off ALL of the black bars in a LBX version save bit rate? I don't wish to change to full screen, just conserve bits for video.

Yes. If your source has black bars above and below the image, and you mask them off with pure black, that should eliminate a lot of noise (slight variations of black in the source) that would otherwise consume bitrate.

To check your arrange method, do this: In the Video tab temporarily set the size to 640x480, which shows 4:3 video properly on the computer screen. Then in the clip frame filter settings, check "Resized image is used to display preview". Then you can set your arrange method there and your clipping and masking while seeing what it will really look like. If different arrange settings look the same in your preview, then they just have the same effect under your circumstances. Remember to set your output size back to what it was supposed to be instead of 640x480 when your done.

[RWANDREWS]

C53248;

Thanks for a very informative answer. I'm sure others can profit from your explanation.