[Charles Caillouet]

Fred wrote:
>I have a 720p/60 sequence that I’d like to put on a simple standard-def DVD using DVD Studio Pro.
>To avoid the gamma and saturation problems I’ve been reading about in this forum,
>I’d like to do a good downconvert from HD to SD and then encode to mpeg-2.
>I’d rather not use Compressor, for all the reasons I’ve been reading about here.
>I do have a Kona 3 card, and I thought I might somehow
>use the Kona to get an SD version of the sequence on my timeline and then
>export a reference movie and encode to mpeg-2 within DVD Studio Pro.
A. What do you think of this path?
B. Exactly how would I downconvert using the Kona?
C. How do I handle the audio?

Fred,

You are addressing several issues and you need to separate them out to get good results.
First, there is a difference among down-converters and they change with each new revision.
I have found in the past that the scaling in FCP, at least for interlace originals (you have progressive), is not that great. I have found that Motion is better. I haven’t found all the switches in Motion, but so far, Affter Effects offers the most options in dealing with interlace and changing frame rates, if you have to go there. There are other apps that i haven’t tried that apparently do even better.

Second, the color encoding equations for NTSC and HD are different. You may find that the luma reproduction is fine but the luma component of saturated colors is different for the two. If you want to see this, take 100% bars from each and look at the difference in the luma steps from white through yellow, on down to blue and then black. If the software doesn’t properly convert between the two, you will get dissapointing results.

Third, these problems also can exist between apps in the same format. There seems to be a disagreement between some apps on what format Quicktime movies arrive in. I don’t know if it because of incorrect tags or inadequate data. I have problems moving edited clips from FCP to Sorenson Squeeze and even some minor ones when i go to the Main Concepts encoder. These can be slight gamma changes to level changes large enough to cause clipping. I have custom filters in FCP to pull levels down and corresponding ones in Sorenson to pull them back up. This can’t be good for signal to noise.

I have several test signals (stairsteps and color bars) that i run through my process and check at the end to see what is working and what is not. Then i compare the actual material in a short test to see if the levels are the same. On top of that, you have to be careful where you monitor because different apps, again, interpret decoded results differently. Obviously, the best approach is to use the same decoder that will be used at the destination, and that is a problem if it won’t be decoded until a consumer gets it.

I don’t know about using the Kona for file-based conversion. Gary Adcock should be able to address that. He is usually on this list.

Audio is another headache. I mux my MPEG2 streams with the Windows app “TransMux” from Pixeltools so that i can include Dolby Digital (AC3) streams from Compressor (was APack). The Sorenson Mux does not deal with AC3 and some of the other options are pretty messy. MainConcepts for the Mac is also not helpful for AC3. If you try to encode AC3 with an older version using APack, be sure to turn off one of your dual processors or it will likely crash.

My solution has been to try different apps and settle on the workflow that gives me the least grief with the best results for each project. The last one that i did used FCP for prep, Motion for down conversion, mcoder for encoding, Compressor for AC3 and TransMux for multiplexing. If you need to go to a standard DVD, then going through DVD Studio Pro should work, but i would compare the FCP and Motion conversion before you decide. The new version of FCP may be better.

hope this helps…

crc