Full or Fast Recompress?

[jimhaddon]

I was wondering, if using Fast processing would give you slightly less quality or not, when encoding with xvid? Im using Virtualdub, with 2 pass encoding. thanx

[UncasMS]

VirtualDub runs in RGB when you use Normal Recompress or Full Processing Mode (in the Video dropdown menu). All of VirtualDub's internal functions and filters run in RGB colorspace only. However, Fast Recompress doesn't decode the video to RGB, and instead just shunts whatever your source is into the compressor you've selected - thus if your source is YUV it shunts the video data as YUV into the video compressor.

This is important because almost all distribution video codecs run in YUV colorspace. This includes DivX, XviD, MPEG1, MPEG2, MPEG-4, DV, etc. HuffYUV (guess where the name comes from) runs YUV colormode natively but you can indeed compress RGB video data with it (but it will be bigger). There's an option in the codec controls to automatically convert incoming RGB video data to YUV in order to save space if you want to.

Thus using Fast Recompress in VirtualDub (or by the same token, NanDub) is not only the fastest way to transcode video but also the least costly in terms of colorspace conversions.

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