Keeping accurate color between source, avisynth/virtualdub and re-encode

[mrwhitethc]

So I'm trying to make sure my simple workflow keeps the correct color information when re-encoding my interlaced blu-ray extras after processing them. Does it really matter? Maybe?

From what I gather HD video from Blu-ray is BT.709.

Mediainfo says the MT2S files are YUV

Frame rate                               : 29.970 (30000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : MBAFF
Scan type, store method                  : Interleaved fields
Scan order                               : Top Field First

I load my files into avisynth with a simple

LWLibavVideoSource("video.m2ts")
QTGMC (Preset=Slow)

Open that in virtualdub and save them in the lagarith codec with the fast recompress option in virtualdub.

This is where I'm confused as lagarith offers YV12, YUY2 and RGB for Modes, so which one to pick?

Once that's done I would like to load the finished AVI back into Handbrake to encode using my x265 1080p preset. There's an option for color space that I normally set to BT.709 if it's Blu-ray or BT.601 SMPTE if I'm doing a DVD.


My questions are what is the correct Mode to use in lagarith?

Do I need to add anything to the avisynth script besides the 2 lines for color conversion?

And should I keep the colorspace as BT.709 in Handbrake? (I believe I've read the decoder / playback device usually defaults to BT.709 if it detects anything above 480)

Thanks for any help!

[poisondeathray]

This is where I'm confused as lagarith offers YV12, YUY2 and RGB for Modes, so which one to pick?

My questions are what is the correct Mode to use in lagarith?

Lagarith is one of the few codecs that does not change the colorspace when the default ( "RGB default") is selected and vdub "fast recompress" is selected. But you can choose YV12 if you want to be certain

Do I need to add anything to the avisynth script besides the 2 lines for color conversion?

The field order before QTGMC, such as AssumeTFF() or AssumeBFF() . HD is usually TFF, 99.9% of the time. If you get the wrong field order, the result will be jerky (but QTGMC can sometimes smooth it over)

(Newer versions of avs+ can convey the field order if it's signalled by LSmash, but it doesn't hurt to specify the actual field order)

Optional: add multithreading such as Prefetch(some number)

And should I keep the colorspace as BT.709 in Handbrake? (I believe I've read the decoder / playback device usually defaults to BT.709 if it detects anything above 480)

Yes

[jagabo]

You can check the color format in VirtualDub2 using File -> File Information. Or add Info() to the end of your AviSynth script. It's most likely YV12 (YUV 4:2:0). Use that in Lagarith. In the final x265 encoding specify BT.709 for Blu-ray sources, BT.601 for DVD sources.

[mrwhitethc]

Lagarith is one of the few codecs that does not change the colorspace when the default ( "RGB default") is selected and vdub "fast recompress" is selected. But you can choose YV12 if you want to be certain

You can check the color format in VirtualDub2 using File -> File Information. Or add Info() to the end of your AviSynth script. It's most likely YV12 (YUV 4:2:0). Use that in Lagarith. In the final x265 encoding specify BT.709 for Blu-ray sources, BT.601 for DVD sources.

Thank you both!!