Doom9's Forum - View Single Post - Do we still need to convert colorimetry of DVD source in vapoursynth?

TheFluff · 11th March 2019, 11:52

Rec.601 was typically used for standard definition broadcast content back in the day, that part is correct, and probably for DVD's originating with broadcast content, as well as older movie DVD's (before HDTV became common). It was never really consistent though, AFAIK. These days you shouldn't need to guess colorimetry if you have an actual DVD or broadcast source - there will almost certainly be metadata that specifies the colorimetry.

That being said, the main reason for converting to Rec601 wasn't that Avisynth didn't handle it (it doesn't matter as long as you're working in YUV, it's only relevant if you're converting to RGB), it was that pretty much all video players and renderers assumed Rec601 colorimetry, so colors would look kinda off when viewing if you kept Rec709 unchanged. These days though you should usually not need to convert colorimetry between SDR colorspaces - just make sure the metadata is kept intact and any decent player will do the right thing when converting to RGB for display.

Vapoursynth (or rather zimg) behaves similarly and will use colorimetry metadata when converting to RGB, if available. I believe zimg will actually throw an error if it can't figure out the colorimetry and you haven't specified it explicitly.

11th March 2019, 11:52	#2 \| Link
TheFluff Excessively jovial fellow Join Date: Jun 2004 Location: rude Posts: 1,100	Rec.601 was typically used for standard definition broadcast content back in the day, that part is correct, and probably for DVD's originating with broadcast content, as well as older movie DVD's (before HDTV became common). It was never really consistent though, AFAIK. These days you shouldn't need to guess colorimetry if you have an actual DVD or broadcast source - there will almost certainly be metadata that specifies the colorimetry. That being said, the main reason for converting to Rec601 wasn't that Avisynth didn't handle it (it doesn't matter as long as you're working in YUV, it's only relevant if you're converting to RGB), it was that pretty much all video players and renderers assumed Rec601 colorimetry, so colors would look kinda off when viewing if you kept Rec709 unchanged. These days though you should usually not need to convert colorimetry between SDR colorspaces - just make sure the metadata is kept intact and any decent player will do the right thing when converting to RGB for display. Vapoursynth (or rather zimg) behaves similarly and will use colorimetry metadata when converting to RGB, if available. I believe zimg will actually throw an error if it can't figure out the colorimetry and you haven't specified it explicitly. Last edited by TheFluff; 11th March 2019 at 11:56.