Reply To: OSSC HDMI output range, SDTV color correction

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March 3, 2025 at 6:35 PM #65226
marqs
Participant

    Marqs, is there any technical reason for HDMI YCbCr output to be Rec. 601? I mean, for unprocessed output I think it is normal but if we want to scale and apply shaders, the TVs will expect Rec. 709 for 720p-1080p resolutions. Rec. 601 is for for 480i/p only, I think.

    The decision to flag YCbCr output as Rec. 601 (more specifically SMPTE 170M) was made early in development when typical output modes were not HD. However, as long as displays read the flag and treat the signal accordingly, it does not really matter even if HD signals get converted to YCbCr601.

    On Pro YCbCr output does not seem to be explicitly flagged which causes displays to treat SD and HD signals differently. However, the conversion matrix is currently fixed (to 709) so either that or the flag should be updated.