Video is Splotchy

[Peter Moore]

Ok here you go:

http://www.mooreusa.net/cfhd%2Dtests/

clip.m2t is a 6 MB splice. Now, Vegas cannot read it directly though HDLink can and with HDLink I created cineform-from-hdlink.avi which is very good.

I found the corresponding frames in the original M2T file and with Vegas made some comparisons. For instance I tried huff-yuv which produced pretty good results though the file is huge. I also tried Cineform directly from a Vegas render, and this is by far the worst of the bunch.

To see the worst of the problem, look to the left of center, near the bottom, at the wall. The noise there is excessive. Granted, it's in the original, but MUCH more subtle.

Hope this helps.

[David Newman]

For some reason clip.m2t will not download -- everything else will. Could you check the filename.

[Peter Moore]

Sorry, I don't know what that's about. I renamed it to .MPG and it works. Just name it back to M2T after downloading.

[Peter Moore]

So, any ideas now that you've seen the footage?

[David Newman]

Seems to only happen in Vegas with dark noisy source elements from the Vegas MPEG decoder -- which we don't recommend you use (as you have found, Connect HD using HDLink does a much better job.) It also doesn't occurs as much less in VirtualDub, or in subsequent CineForm renders out of Vegas, neither of which use the Vegas MPEG decoder. That rules out a DirectShow vs VFW issue -- it also rules out medium vs high quality encoding (as both modes produce excellent results outside of Vegas.) I think we are chasing ghosts here (the noisy MPEG variety.) The noisy 8-bit nature of the video is the primary problem. The region you are having issues with are very dark with Luma level ranging between 20 and 30, with about noise level between 1 and 3, so noise is a huge factor for these very dark regions. Enhancing the source shows clear MPEG macro blocking in the regions affected. The reason Vegas has a slightly harder time is its RGB nature (Aspect HD and Premiere export using YUV as much as possible), so the noise + the low signal + YUV to RGB conversions are most of what you see. Lossy compression is a factor, yet my testing (particularly which change the compression quality) shows that it isn't a significant element. Using uncompressed or HUFFYUV eliminates the color conversion for accurate noise reproduction, so you do have that option of your final masters.

Note: the preview window with Vegas shows the video at the wrong levels, broadcast black (IRE 7.5, Y 16, cgRGB 0,0,0) is displayed at RGB level 16,16,16. This is give you an artificial amplification of shadow noise, that will be far less visible on standard outputs.

[Peter Moore]

I very much appreciate you taking the time to look at this.

So what you're saying is, Vegas' M2T decoder does the poor job? If I keep the source files as Cineform, and then subsequently re-render them using Vegas or other software, there won't be a problem? I'm gonna try that right now, and if so, you have solved my problem.

[David Newman]

Yes that is basically it. The "splotchy" was mostly noisy reproduction of an MPEG artifact, yet this is greatly suppressed in HDLink to produce nice images. So if you don't go back to you MPEG source, and stick with CineForm Intermediate you will get better results.

[Peter Moore]

Yeah I am definitely getting better results now, although the 2nd generation Cineform encoding from Vegas still has a noticeable difference from the 1st gen. Is it supposed to be re-encoding from Vegas even with no modifications? Just cuts?

[David Newman]

Unfortunately not. Vegas doesn't support the 2 frame GOP structure of the CineForm Intermediate codec for direct copy, so it will re-render to a 1 frame GOP when you export. The third generation (if you were to do that) would be direct copy, as 1 frame GOP are support by Vegas. I think the idea for Vegas users might be an option to select a 1 frame GOP length within HDLink, that cuts only renders are lossless and fast, however this has the downside of creating bigger files and a little slower playback.

[Peter Moore]

That would be nice.

I'm sorry but the pass out of Vegas is just still too splotchy. It's a shame, because the pass out of HDLink is excellent. After my 24p processing in VirtualDub, it's still excellent. But as soon as I output one more CFHD round through Vegas, the splotches are still very bad. Vegas just does not handle this codec correctly.

I tried to make subclips to avoid multiple generations, but Vegas won't even let you use subclips between projects. I guess the only option is to switch to Premier. Down the road, though - have to finish this project first with what I've got. Again, thanks for the help though.

[Pierre Barberis]

All the urls point to a surprising blue page with a dart target board absolutely unrelated to MiniSplit.

Would any one either suggest a working link or post the file somewhere ?

Thanks

[David Newman]

That is odd as the link still works for me. You could just google "MiniSplit" if you browser can't show the page I found.