YPbPr in Color Space: 601 or 709?

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  • #27199
    cerolero
    Participant

    I have my Wii connected to the OSSC via Component, and while going through the settings I noticed this option. Changing it seems to change the colors a bit. On Junkerhq it says that Rec. 601 is used for SD content and Rec. 709 is for 720p and higher. I’m using 2x mode so the resolution is 960p, but using the “Auto” option for the color space makes it default to Rec. 601, despite being a higher resolution than 720p. So does the OSSC decide the color space based on the “passthru” resolution, so to speak?

    Also on Junkerhq under “TX Mode” it says “HDMI (YCbCr444): 24-bit YCbCr 4:4:4 (Rec. 601) output with audio and auxiliary Infoframe packets. Recommended for displays which do not support RGB in full-range.” So does this mean that I need to set either HDMI (YCbCr444) + Rec. 601, or HDMI (RGB) + Rec. 709 to get accurate colors?

    Thanks in advance!

    #27203
    nmalinoski
    Participant

    You will get accurate colors as long as you leave “YPbPr in Color Space” at auto.

    “YPbPr in Color Space” means “YPbPr input Color Space” (that’s how it appears in the manual), so it is only used for interpreting incoming YPbPr signals (I believe the OSSC uses RGB internally). Leaving it at auto will let the OSSC correctly use Rec. 601 for SD and ED content and Rec. 709 for HD content.

    As for TX Mode, you should leave it set to HDMI (RGB) unless you need some specific compatibility offered by the other two output modes, such as if your TV or downstream video processor cannot handle 4:4:4 RGB (Use YCbCr 4:4:4), or your AVR (like mine) won’t fall back to TOSLINK when the OSSC is in HDMI mode (use DVI).

    As for using Rec. 601 for output, marqs will probably have a better explanation, but, my [limited] understanding is that HDMI (ostensibly) allows for indicating the color model and color space, and Rec. 601 is a generic standard for encoding YCbCr/YPbPr (whereas 709 is specific to HDTV 720p/1080i/1080p modes); so, as long as the display understands that the color model is YCbCr and the color space is Rec. 601, it should be able to accurately decode the video.

    #27204
    paulb_nl
    Participant

    The Rec. 601/Rec.709 setting is for the input color space for converting the YPbPr signal to RGB. http://junkerhq.net/xrgb/index.php?title=OSSC#YPbPr_input_Color_Space

    The signal from the Wii that the OSSC receives at its input is 480p so it should be set to Auto or Rec 601.

    You should stick to TX mode RGB for best quality and accurate colors. If you select YCbCr444 then it will convert the output from RGB to YCbCr Limited Range (16-235) and the receiving device has to convert it from YCbCr to RGB again choosing Rec 601/709 so you’ll want to avoid that.

    EDIT: Too late 🙂

    #27209
    cerolero
    Participant

    Thank you both so much for making it all clear, I really appreciate it! Good to know from now on when I add more consoles that uses Component instead of RGB SCART.

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