This content has been marked as final. Show 10 replies
I also am curious if anyone else has discovered that QT (maybe) or AME lifts the Levels (including Blacks)
I have a workflow that includes export to QT via Media Encoder for Broadcast TV and have a suspicion that QT (or FCP) does something to my levels.
Currently doing tests on the issue.
There are known gamma level issues with QT between platforms.
> AME lifts the Levels (including Blacks)
> There are known gamma level issues with QT
I don't know what the issue is, but gamma should not affect black.
Not all blacks in an image are true black (shadows), and they will be affected by a gamma (midtones) shift.
Hey Jeff. Do you know where I can get more info on the issue.
Hey Craig --
I think I undersand what's going on: You say this happens with all formats (not just QT), right? This is because Premiere always maps RGB 0-255 <-> YUV 16-235.
Any exports via AME force an intermediary RGB conversion -- even if the output is YUV (MPEG2, H.264).
I'm not sure about QT but in Video for Windows (like .avi) the RGB->YUV transformation is handled by the codec, not the interface.
Many DV codecs for example (Matrox, Canopus, Cedocida) allow you to choose the way these range conversions are handled. It Matrox parlance, there is "Standard" (16-235) and "Expanded" (0-255).
The only way I've found to preserve the full range of YUV sources (including superwhites and superblacks) from Premiere is to export with DebugMode FrameServer in YUY2 mode. The caveat here is that sources that are RGB (or made to be RGB by applying filters) will always be scaled to 16-235 when output as YUV.
In some ways none of this matters: MPEG2 DVD, for example, should always be limited to this range. Furthermore most media players, etc. will convert YUV 16,235 <-> RGB 0,255 also, so it should appear correctly on playback in any case.
Does this make sense?
I will read and absorb what you have taken the time to explain.
Note: I was not aware of the issue when my workflow was all "avi" and just started to notice it now I export 720P QT as Apple Component YUV 24Bit
I guess what I'm trying to say is that, most of the time, this is what you want to happen. In cases where it's not... you're out of luck :)
My Matrox system, however, does have a "Post Production" editing mode in Premiere that uses the entire 0-255 range in both RGB and YUV. If I edit in this mode and export "Matrox AVI" I can preserve the entire range. I know that won't really help you, but I figured it was worth mentioning. For me, this is a very cool feature of the RT.X2, since I often deal with full range input/output in Premiere.
One way to slightly improve export quality - as I've found it - is to put your project files in a separate sequence and then apply LEVELS to it where black(rgb)=16 and white(rgb)= 235.
To my eyes at least this feels fetter.
Just a suggestion.
This is mostly directed towards Dan, but anybody else's experience is appreciated: how does AME scale the 256 range ? I did some tests and saw a huge shift of lumas in the ~240 range. However legal lumas at 160 did not seem to change much. This was all eyeballed so I might be wrong, but does AME do some kind of dynamic compression rather than linearly scaling 0-255 to 16-235 ?