YV12 in AviSynth 2.51 unable to be used in TMPGenc or CCE
 

From Doom9.org:

"Is YV12 & AVISynth 2.5 just for Xvid/DivX or can it be used for conversions to MPEG1 or MPEG2 (DVD to (S)VCD) via TMPGenc or CCE? Or do these 2 encoders not support YV12?

Neither CCE nor TMPGEnc can use YV12 input since Windows has no internal YV12 compressor. This only means that the last line of AviSynth must be a ConvertToYUY2 (for CCE, or ConvertToRGB24 for TMPGEnc) call, and that you will not be able to take full advantage of YV12 colorspace. Still there are two advantages:

1) All internal filtering in AviSynth will be faster though (less data to filter, better structure to filter, and a very fast conversion from YV12 to YUY2), and you will definitely be able to tell the difference between v2.06 and v2.5.

2) If you are making a progressive clip there is another advantage. Putting off the YV12->YUY2 conversion until the end of the script allows you to first IVTC or Deinterlace to create progressive frames. But the YV12 to YUY2 conversion for progressive frames maintains more chroma detail than it does for interlaced or field based frames.

The color conversions:

CCE: YV12 -> YUY2 -> YV12
TMPGEnc: YV12 -> RGB24 -> YV12

If you have DivX5 or XviD installed, it will do the necessary conversion automatically. I use AVS2.5 all the time without any problems, and no need to add ConverttoRBG24() or ConverttoYUY2() in the AVS script.