[Adam Goral]

I have a few more questions for you folks if you’ll be so kind as to entertain me…

After noticing that the contrast much significantly lowered when using MPEG Streamclip to transcode from XDCam EX to DNxHD rec709, I looked at both under a waveform monitor. The black levels on the original XDCam EX clip are right around zero, but one the DNxHD clip they are raised to around 13 or so.

I tried transcoded the original again but using DNxHD and RGB colorspace and the result was much closer to the original under the waveform, but the blacks were a bit darker and generally a bit more contrasty. I also tried keeping the 709 colorspace but increasing the contrast from within MPEG streamclip to about %117 and it matches the originals waveform almost exactly, but there is an unacceptable amount of noise introduced.

I really want to provide my editors with the best quality material possible and while I am sure we could grade the DNxHD 709 footage with raised blacks back to normal, I do not want to have to spent my precious color grading time on that when there are more important scenes to deal with.

So here is the breakdown of what I’ve notice:

Original XDCam EX: blacks 0 IRE
DNxHD rec709: blacks %13 IRE
DNxHD rec709: blacks %0 IRE with %117 contrast adjustment during transcode
DNxHD RGB: blacks %-2 IRE

[Adam Goral]

Thanks Craig,

What I have do so far, which seems to be working well, is I installed Avid’s codecs on my Macbook Pro and used MPEG Streamclip to transcode straight to QT wrapped DNxHD. I then imported the clips into our Avid project and they seems to be working fine. I do not detected a noticeable loss in quality, but the image is definitely brighter. A simple contrast adjustment proved that I could pull it back down to match the original file with minimal effort, but even still I wondered why this happens? A friend said that Avid likes to “brighten things up a bit”, but that’s not much help…

Any thoughts?

-=adam=-