IYUV vs Raw AVI?

[jcdenton]

I notice captured video in IYUV format is roughly half the file size of raw AVI. Since IYUV is supposed to be a lossless codec, is there any reason to use raw AVI vs IYUV?

Thanks.

[Sulik]

Uncompressed AVI can support many different frame formats:

RGB is 4:4:4 RGB (24bpp)
YUY2/UYVY are 4:2:2 YUV (16bpp)
YV12/IYUV are 4:2:0 YUV (12bpp)

Your source from analog capture really is 4:2:2 YUV (full luma resolution, half horizontal chroma resolution), and is the only truly lossless format.
Capturing to uncompressed RGB is a waste of CPU and disk space.

The problem with YV12 and IYUV is that you're not only losing half the chroma resolution, but the decimation will ignore weither the frame is progressive or interlaced (AVI tends to assume everything is progressive), so it might create even more artifacts.

Bottom line: if you want to capture uncompressed AVI, ALWAYS stick to YUY2 or UYVY.

Note: If you're capturing at a low resolution of 352x288 or less (single field), then you can use YV12 or IYUV.

[jcdenton]

Thanks! In VirtualDub, the only one I have available is IYUV. Is there a way to utilize the other codecs in VirtualDub?

Also, the files I am working with are VHS captures which have already gone through a compression into 1500 kbps DivX. I am converting them to a lossless codec so I can edit them without having to worry about keyframes. So, with that being said, do you think I should worry about using IYUV since the files are already of less than perfect quality?

[Sulik]

If the files are already compressed (DivX or MPEG), then by all means keep it as IYUV or YV12 (you're not losing anything as it's the format of your source - DivX & MPEG use 4:2:0 YUV, a.ka. YV12 or IYUV ).

[jcdenton]

Great, thanks.

[dwiesel]

Sulik…how does YUV2 fit in the compression equation/rules? This is what I capture in..is it comparable and as good as YUY2? Also, if these are lossless, I can't understand why my I get a smaller YUY2 file when I render it from YUV2?

Many thanks.