It means the yuv values have full range, 0..255, as used in jpeg files. Most video uses so called studio swing, with Y 16..235, UV 16..240.
Using the wrong range when converting to RGB can cause the video to look faded, or artificially color boosted.
--
You received this message because you are subscribed to the Google Groups "Codec Developers" group.
To unsubscribe from this group and stop receiving emails from it, send an email to codec-devel...@webmproject.org.
To post to this group, send email to codec...@webmproject.org.
Visit this group at https://groups.google.com/a/webmproject.org/group/codec-devel/.
For more options, visit https://groups.google.com/a/webmproject.org/d/optout.
Does it make any sense of artificially reducing color space from 8-bits to around 7.7 or 7.8 bits? (in YUV420)
Not really, it is a legacy thing. Analog video signals sometimes used to code things in lines beyond the screen in super-white or super-black, like TeleText etc.
If so, maybe limit new formats like AV1 to use only "yuvj" ?
This will improve precion slightly.
i-mode:
Plus things like interlaced (i-mode) mode doesn't seem to make much sense, at least to me.
Does it?
Cutting old / legacy modes can make the codec simpler to implement, understand and reduce amount of bugs. (plus maybe improve quality slightly)
You don't want to convert input since conversion is not lossless.
Ronald
You have to keep in mind there is a lot of hardware out there like digital TVs that expects the values to adhere to these existing standards. You can't just change it at will. If you want more fidelity you can use 10 bit data, see the BT.2020 standard.
>You don't want to convert input since conversion is not lossless.
up or down value by one is visually lossless. And for a lossy codec that's acceptable tradeoff.
I thought that digital TVs use RGB888 color space, just like PC does, and yuvj fits better for the PC use case.
>Were you thinking of reducing the bitrate when you asked "Does it make any sense of artificially reducing color space from 8-bits to around 7.7 or 7.8 bits? (in YUV420)"?
Nope, I was thinking about increasing quality a bit, from 224 possible values (7.8 bits) up to 256 values per channel (8 bits).