[FFmpeg-devel] [PATCH]lavc/pgssubdec: Fix palette colourspace

Jan Ekstrom jeebjp at gmail.com
Sun Apr 17 20:41:32 CEST 2016

On Sun, Apr 17, 2016 at 9:21 PM, Reimar Döffinger
<Reimar.Doeffinger at gmx.de> wrote:
> In particular, I have an uncomfortable suspicion that
> PGS might be designed to match the movie's colour space,
> in which case neither variant would give correct results
> but instead it would have to depend on what format the
> corresponding video track uses (and it probably would
> be more than just the 255/224 factor that would differ).

Yes, the YCbCr values in palettes are matched accordingly against the
video stream. As per the specification:
"Y, Cr and Cb shall have the same color matrix as the associated HDMV
Video stream: 525-60/625-50 (Rec.601); 1080i, 720p (ITU-709)"

Otherwise the specification notes that valid values in palettes are:
-Y: 16-235
-Cr: 16-240
-Cb: 16-240
-Transparency: 0-255, where a value of ‘255’ indicates full opacity
and ‘0’ indicates full transparency.
(Each Palette entry shall have a default transparency value of 0; the
default values of Y, Cr and Cb are undefined.)

Best regards,
Jan Ekström

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