Whilst I am still not sure where this is going, I have done some follow up experiments.
It seems quite clear, from reading around the subject that it is not uncommon for video encoding to lead to colour changes. The ability of the user of any encoder to influence this process may also be limited or non-existent.
To illustrate the variables :-
Use a red colour board 247,32,48 in track 1, above a green colour board 60,125,52 in track 2.
Confirm the RGB values using colorpic or similar - on my timeline they are exactly the same.
Analyse the RGB values in the preview window with the same tool.
Using VMR7
red 255,75,68
green 78,137,68
Using VMR9
red 247,31,48
green 60,126,52
Immediately (on my system but maybe not on others??) it is both visually obvious, and analytically obvious, that using VMR7 as the preview renderer gives significantly different colour to the timeline, whereas using VMR9 as the preview renderer giving virtually the same RGB values as the originals.
Therefore, from a visual perspective, the choice of renderer may be crucial to the displayed preview colour of the edited video content - easy to spot with block colours, but not so easy with normal content.
Which colour does PD export? One would expect the timeline RGB values, irrespective of the preview values. But, and here is the key issue, once exported how can we tell?
Presumably, unless we can analyse the file metadata, we have to play the produced video.
I exported the two colour board timeline in two resolutions for both .mp4 and .m2ts formats. If the produced file is played in different media players, there is a marked visual and analytical difference in RGB values, depending on the player.
The attached file "mp4 comparison" visually illustrates the difference, with the produced video @640 on the left and @1080 on the right.
The players are, from left to right, MPCHC, VLC, WMP and QT.
The screen shot should not be used for analysis as it is different to the original display but VLC is the only player that is virtually correct to the original timeline RGB values.
Similarly the file "m2ts comparison" produced @720x480 and @1080 also shows marked differences. The format and layouts are the same but this time QT is not available to be used. Again VLC is the closest player to the original.
Perhaps other players will display different results again?
So do we have a reliable and consistent methodology that allows us to analyse the colour encoding performance of PD - perhaps yes if we keep all the variables consistent on our own systems, probably no for any other system with differing variables.
If we cannot control the viewing platform, it seems unlikely that we can rely on the colour presentation being as we produce it on our own system, irrespective of PDs performance or file format or preview renderer or raw content or video card etc etc.
I suspect the best we can do is make the best shot at it for our particular purposes, however that is achieved??
Cheers
Adrian
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Life is really simple, but we insist on making it complicated. (see below)
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