codecs/color space for separate encode stages question

[spiritgumm]

basic question about color space and codecs when using avisynth and vdub.
Does choosing a compression codec dictate what colorspace the video will be? I know the video can remain YV12 when using Vdub Fast Recompress setting, but if I'm doing a dvd re-encode in separate lossless stages - Step 1 making it progressive in Avisynth (Fast Vdub), Step 2 using Vdub filtering(Full Vdub), Step 3 clean up in Avisynth (Fast Vdub), should I be using codecs which compliment the next step? Or are the codecs irrelevant and I use converttoRGB and converttoYV12 when appropriate in the scripts?

I was using UT Video 420, and Mediainfo wasnt reporting the colorspace correctly, so I got to thinking that if the codec could dictate the color space, maybe that would be less damaging than using a script conversion command. UT Video seems to have codecs that might be color space-specific.

[poisondeathray]

Does choosing a compression codec dictate what colorspace the video will be?

Yes it can, if that specific codec only supports a specific colorspace. For example UT has specific fourCC's for each colorspace

e.g. You use vdub filters (RGB), but export UT 420 => this will force conversion to YV12 using Rec601 in the export whether you wanted to or not

I know the video can remain YV12 when using Vdub Fast Recompress setting, but if I'm doing a dvd re-encode in separate lossless stages - Step 1 making it progressive in Avisynth (Fast Vdub), Step 2 using Vdub filtering(Full Vdub), Step 3 clean up in Avisynth (Fast Vdub), should I be using codecs which compliment the next step? Or are the codecs irrelevant and I use converttoRGB and converttoYV12 when appropriate in the scripts?

I was using UT Video 420, and Mediainfo wasnt reporting the colorspace correctly, so I got to thinking that if the codec could dictate the color space, maybe that would be less damaging than using a script conversion command. UT Video seems to have codecs that might be color space-specific.

If mediainfo is reporting incorrectly, you can add info() after the source filter in the script

If you can replace vdub filter with an equivalent avisynth filter, then you don't have to round trip into RGB land

[spiritgumm]

I doublechecked the 420 UT video by running it in AvsP with Info(), if that's what you mean.
I'm using Deshaker in Vdub (a project from awhile ago which you helped me), so RGB is necessary.
I noticed the UT file is alot larger than a Lagarith outputted file, but I imagine UT is faster.
Anyway, is it any less harmful to use a specific codec (UT RGB or 420) rather than command lines and Lagarith?

[poisondeathray]

Yes, UT is waaaay faster, and scales better with more cores, but less compressed

Lagarith is fine (supports 420,422,RGB), if you have it setup correctly - it will automatically use the same colorspace as input file. You can prove this yourself with info()

Anyway, is it any less harmful to use a specific codec (UT RGB or 420) rather than command lines and Lagarith?

If you're in the same colorspace, it's the same. Lossless = Lossless

[spiritgumm]

If you're in the same colorspace, it's the same. Lossless = Lossless

I had read that converting back and forth was "damaging." I dont suppose you're saying that using color space-specific codecs avoids this?

[poisondeathray]

If you're in the same colorspace, it's the same. Lossless = Lossless

I had read that converting back and forth was "damaging." I dont suppose you're saying that using color space-specific codecs avoids this?

Yes, RGB<=> YUV is "damaging" regardless of codec, colorspace specific codec's don't avoid this

Lossless RGB<=> Lossless RGB isn't damaging (same colorspace, and no compression losses)

Lossless YV12 <=> Lossless YV12 isn't damaging (same colorspace, and no compression losses)