Color Conversion

[SameSelf]

This is probably an esoteric question, so hats off to anyone who can confidently answer one way or another!

Here is my problem. I am frameserving out of PPro using Debugmode Framserver which gives me the option of outputting the video stream as either RGB24, RGB32, or YUY2. I select YUY2. From here I process the signpost.avi in AVIsynth and encode using x264. Here is my uber simple AVS script that works flawlessly from what I can tell:

AVISource("E:\signpost.avi", audio=false).AssumeFPS(30000,1001)
ConvertToYV12()

However, I have noticed that I can leave the ConvertToYV12 line out, and x264 proceeds but with the following "warnings"

resize [warning]: converting from yuyv422 to yuv422p
resize [warning]: converting from yuv422p to yuv420p

So, my question is whether it is preferable to let AVIsynth do the color conversion? or let x264? or does it not matter?

[poisondeathray]

If it's progressive YUY2, you will get identical results and it won't matter. x264 will use bicubic kernal with swscale, ConvertToYV12() with default settings will use bicubic kernal. Letting x264 do it might be very slightly slower, because it might be re-arranging the 422 plane arrangement before converting to 420

You would want to use avisynth when you need more control over something. For example if you needed Rec709 matrix when converting from RGB, or interlaced conversion, or maybe you wanted to use other chroma sampling algorithms or placements

[SameSelf]

Wow, that really nailed the question on the head, pdr. Thanks. It is indeed progressive YUY2 in this example. But it may not always be. So it sounds like stick to AVIsynth.