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h264 color shift: time to solve
So h264 seems to shift colors and desaturate things in weird ways. At least through compressor or QT components. Haven’t done a shoot out with my matrox h264 card yet.
I assumed for a long time that quicktime was double-overlaying or ignoring my monitor’s colorprofile, and that a quicktime bug was responsible. As most users don’t create monitor profiles, I assumed I was fine.
However I suspect that the conversion is simply innaccurate.
I’m guessing that it should be fairly straightforward to generate a LUT to solve this. (assuming REC709 to compressor H264). I would do it myself if I had the time and resources, but likely won’t get to this for a few months.
If anyone has the time to make this, I’d be willing to pay for it. And I’d bet that I’m not alone.
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4 Replies
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The solution is fairly simple: use a differed encoder than QuickTime or Comprssor. Even x264 for QuickTime (open source project) will produce vastly superior files than QT it self. Other options include a third party encoder like Episdoe or Squeeze.
A problem I’ve found is different formats in will also very much affect your output, hence you might be required to adjusts outpu based on this. Large downscales will also affect the sharpness of an image, hence you have to compensate for that. And so forth.
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Erik Lindahl
Freecloud Post Production Services
http://www.freecloud.se -
Erik,
I assumed that x264 was a different (open source) codec to h264. In that the end user must have the x264 codec installed on their machine. So while it may be a superior codec, its not a universal one.
Am i wrong in that regard?
Have you found that Sorenson gets you something accurate? Tested across Non-CL, CL and PC quicktime platforms?
I’m pretty sure ther problem with compressor h264 is a metadata problem where CoreVideo hardware accelleration results in a different image than the actual codec itself. For example I believe the same h264 will correctly map on a PC or older mac. If squeeze is getting better results, I wonder if its on the metadata level.
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x264 is as far as I understand it an open source project based on the h264-standard. In theory you could create files there that aren’t playable on h264 devices. However, the same goes for almost any h264 encoder. Different playback environments differ in how much of the h264-stanard they support.
I use x264 through Episode (yes, it kicks the s-it out of the encounter in the application in both speed and quality) daily and it works great. Files playback on Macs and PCs via QuickTime Player or VLC as well as iPhones and iPads
Keeping sustained color accuracy between different playback environments is however very hard if not impossible as the decoder, OS and esp. the screen will differ a lot. This is just something we’ll have to live with until some kind of unified standard comes (which I have a hard time seeing happening).
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Erik Lindahl
Freecloud Post Production Services
http://www.freecloud.se -
We use the matrix encoder, and we’ve had outstanding results. They recently released updates to address iPad h264s at 24p.
They also have options for colour space conversion, hardware scaling, and hw noise reduction.
Cheers
David
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