Compression quality issues
by Walter Miale
on
Jul 1, 2009 at 5:31:36 pm
We are working with graphically rich material of abstract images from footage shot on dv and heavily filtered. When this is put through Compressor (90 minute, two pass, best quality), the result is unacceptable. It lacks clarity and transparency, and shows what I take to be noise. Please suggest solutions, if any.
Is it possible to make a DVD which will play on computers (if not home players) and which has functional menus--and which uses uncompressed dv sequences?
Would a cine look filter help? If so, where can we find one? We don't see one in FCP.
Would it help to cut a Blue Ray disk? Can Blue Ray disks be played on most computers?
Re: Compression quality issues by Michael Sacci on Jul 1, 2009 at 6:30:41 pm
[Walter Miale]" It lacks clarity and transparency" What in the world does lacks transparency mean?
[Walter Miale]"uncompressed dv" There is no such beast to begin with, DV is very compressed for an editing codec 5:1, as well as low color space 4:1:1
but the answer is if you are authoring a DVD it will have to be m2v video which is even more compressed then DV.
To get the best results of graphics you need to do one of two things, Not place them within a DV timeline or codec. Uncompressed 10-Bit or ProRes is much better.
If you have to place them in a DV timeline because of your workflow, do NOT render the timeline. Export the timeline Using Compressor. IF you can use a high bit rate (6-7 Mbps) use CBR method. This will give you the best results. Note, FCP and Compressor will be tied up while doing the encode but the CBR will be much faster. Make sure you encode the audio as ac3 to give the video more bitrate and will playback better. There are post on how to encode ac3.
[Walter Miale]"Would it help to cut a Blue Ray disk?" Not if you are starting out with SD DV footage, a waste of time and expense and...
[Walter Miale]"Can Blue Ray disks be played on most computers? " NOPE, computer has to have a bluray drive and they are only on a small percentage of system.
Re: Compression quality issues by Walter Miale on Jul 2, 2009 at 1:35:08 am
Thanks very much for the info.
The sequences look better with one-pass cbr. I tried a couple at 7.2 average mbps. 7.0 would be safer?
Sorry for the stoopid Q, but when I dumped some render files in the trash, the project file didn't notice. The timeline didn't show anything needing rendering. How should I "unrender" the sequence? (I'm using FCP 6.03 in Leopard, but my mind is still back in FCP 3.)
Complete unrendering looks problematic because in a number of cases, clips in sequences are themselves render files, no doubt as a result of our twisted workflow.
Re: Compression quality issues by Michael Sacci on Jul 2, 2009 at 2:18:48 am
if you disable a clip it should go unrendered when you enable it. May want to test a short section before you go unrendering a lot.
there is also a Render Manager under Tools in FCP.
Personally I think you get like gain over 7.0 so I use that as my max (with ac3 audio) but I know people go as high as 7.5, remember even with CBR rates can spike but not as much as with VBR. Also if you are going to full replication (vs DVD-Rs) you can push the bitrate up without any worries, The 7 ceiling is more for DVD-Rs, but since I want the client to see the end result and have it plan back smoothly I keep the 7 ceiling for replication disc also.
Re: Compression quality issues by Walter Miale on Jul 2, 2009 at 6:46:42 am
You wrote: "To get the best results of graphics you need to do one of two things, Not place them within a DV timeline or codec. Uncompressed 10-Bit or ProRes is much better."
When I try to place the raw captured clip in a sequence set to Uncompressed 10-bit, I get a window telling me. "For best performance, your sequence and external video should be set to the format of the clips you are editing." I'm confused. The clip was shot in dv and I presume captured with dv NTSC 48 kHz. I would try to recapture it, but the Log and Capture window (FCP 6.03) does not offer the options you recommend.
Re: Compression quality issues by Michael Sacci on Jul 2, 2009 at 1:25:51 pm
that is why there are 2 options. If you are editing in DV because that is what your footage is, that is fine BUT don't render the graphic or do a export to self contained movie. When you render down graphics you are introducing a lot of compression and lowering the color space of the graphic, which is why you loss quality.
SO you leave the graphic unrendered, and use the Export>Using Compressor from the FCP timeline, make your m2v and that should give you the highest quality for you graphics. I suggest trying a short section to test the results.
Re: Compression quality issues by Walter Miale on Jul 2, 2009 at 3:15:52 pm
Thanks again.
I understand the principle, and that one should export unprocessed timeline to Compressor. I did a couple of tests and it works. But Just to be clear: when one captures dv footage into FCP, one should edit in (not uncompressed but in) dv - NTSC? There is nothing to gain in terms of color space etc by editing in uncompressed mode?
And what about workflow? So that one can see what one is doing, do you recommend rendering as one goes and then trashing the renders from the desktop, or what? It gets complicated when one copies clips and sequences from file to file. Always de-render before copying I guess, yes?
Re: Compression quality issues by Michael Sacci on Jul 2, 2009 at 6:56:39 pm
With DV, if you capture as 10-Bit Uncompressed or ProRes which are both 10-bit and 4:2:2 you have bigger files with no quality gain but everything you do in your post process will retain higher quality especially added graphics and give you more room to color correct. So if your project has a lot of graphic it maybe worth the extra steps. The fastest way to get your footage out of DV is to have a deck with SDI (they are not the cheap DV decks) so instead of capturing via DV you capture ProRes or Uncompressed.
