Originally Posted by mahlerfan999
Thanks Bill for the clarification! I didn't realize that in practice the players still usually output to 601.
Yes, but it is so hard to be precise. At least in the three players I have tested, the RGB content from the DVD stays the same, as originally recorded using the SMPTE-C colors. But, after upscaling, the RGB was re-encoded into YCbCr with the Rec709 color encoding matrix. So, technically speaking, most would say it was re-output at Rec709.
For SD players, my test process for this was to measure the color points on the set, after sending the data in 480i or at 1080i. If the player moved the RGB values, one would see the measured red/green/blue primaries move at the set, and they don't. For the blu-ray player, I performed the same test using the GetGray SD calibration DVD, compared to the AVCHD blu-ray DVD. Again, the colors measured at the set did not move.
Of course, if the content actually carried the color-space flag saying which primaries were used when the material was recorded, the set itself could move its primaries based on the flag. So had the color points moved, there would still be a question whether it was the player remapping the colors, or the set adjusting its color gamut.
(Obviously I found this subject hugely interesting, especially as more than half my DVDs are foreign and PAL, with an even different color gamut.)