2015-01-27, 04:17 PM
To use luma from a source, and chroma for another, the two sources should be spatially aligned; but it's an almost impossible situation - no problems with eventual temporal difference, it is still possible to repeat/delete eventual frames.
Of course, it's still possible to upscale one source to have the same resolution of the other, but it's very difficult that all the frames will align perfectly with just one upscale setting...
In the eventual case you have two perfect spatially aligned sources - let's say, one with "wrong" color grading, the other with too much edge enhancement, it's possible to take the luma from the first, the chroma from the second and align them - really simple to do with avisynth; but there is a really remote probability to have those...
Usually, what really happens is to use the luma of a good quality source - like BD for example - that has a "wrong" color grading, and use the chroma of another source - like DVD - as COLOR REFERENCE; what does it mean?
For example, for my "Halloween" project, I took the luma from the 35th Anniversay BD, and the 1999 THX DVD was used as color reference; an avisynth script "extracted" somehow the color informations from the DVD, and applied them to the BD; this does not always a perfect job (at least, using my script), but with this movie, it made a wonderful job, leaving just few shots not perfectly rendered and I just fixed them manually.
Another way is to adjust the chroma of a source to look alike another source; this is a painful job, because it's almost impossible to find a single setting for the whole movie; at the contrary, any scene (and sometimes any shot) should be fixed using different settings... with this method, a very well optimized monitor and a LOT of time and patience, it is possible to get a final product with a perfectly matched color grading!
Of course, it's still possible to upscale one source to have the same resolution of the other, but it's very difficult that all the frames will align perfectly with just one upscale setting...
In the eventual case you have two perfect spatially aligned sources - let's say, one with "wrong" color grading, the other with too much edge enhancement, it's possible to take the luma from the first, the chroma from the second and align them - really simple to do with avisynth; but there is a really remote probability to have those...
Usually, what really happens is to use the luma of a good quality source - like BD for example - that has a "wrong" color grading, and use the chroma of another source - like DVD - as COLOR REFERENCE; what does it mean?
For example, for my "Halloween" project, I took the luma from the 35th Anniversay BD, and the 1999 THX DVD was used as color reference; an avisynth script "extracted" somehow the color informations from the DVD, and applied them to the BD; this does not always a perfect job (at least, using my script), but with this movie, it made a wonderful job, leaving just few shots not perfectly rendered and I just fixed them manually.
Another way is to adjust the chroma of a source to look alike another source; this is a painful job, because it's almost impossible to find a single setting for the whole movie; at the contrary, any scene (and sometimes any shot) should be fixed using different settings... with this method, a very well optimized monitor and a LOT of time and patience, it is possible to get a final product with a perfectly matched color grading!