Compressor MPEG2s look blocky

Here's a weird problem I have experienced since I've been using Compressor:

When I output a project to MPEG2 using Compressor, it looks a little "blocky" on my 32 inch HDTV monitor when played on a standard DVD player. The way I have been making DVDs for the past several years has been to lay my edited project back to HDV tape, and then play that out of my Sony Z1U downconverting to standard def. and recording on a Panasonic DVD recorder, stripping the MPEG2 and the AC3 off the disc using MPEG Streamclip and make my authored disc with menus in DVDSP.

There are 2 things I notice between the different processes: The volume on the audio going through Compressor is significantly lower than the audio recorded on my DVD recorder...maybe because there's an AGC on the DVD recorder. But secondly, the footage going through Compressor looks a little jaggy, blocky, or whatever you want to call it. In my opinion, it looks like a slight Mosaic filter has been applied, when compared to the DVD recorder.

I'm not sure what the cause of this is...and it's a bit frustrating, because I would like to take advantage of Compressor more, but this quality problem is obvious, not the kind of thing where 9 out of 10 people wouldn't see it, but probably 2 out of 10 wouldn't see it.

I've been hanging out on a recent ProRes thread, and I'm wondering if the fact that I haven't been using it is what's contributing to this problem.

Any thoughts?

Thanks!!!

>In my opinion, it looks like a slight Mosaic filter has been applied, when compared to the
>DVD recorder.

That may be caused by the downscaling. Downscaling usually results in aliasing. Graeme Nattress will probably give you much better insight on this.

To downconvert frame size properly in Compressor, you need to turn on Frame Controls and set the resizing filter to either "better" or "best", but you will be sacrificing time for quality. The result will probably beat sending out your footage to a set top recorder (from which you will lose an analog generation and worse if you are sending out a composite signal).



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So the default settings for "Best Quality 120 min DVD" need to be changed? I'll check that out.

Also, the footage coming out of my Z1U is coming out firewire into the DVD recorder.

>So the default settings for "Best Quality 120 min DVD" need to be changed?

Not exactly. "best quality" for DVD usually assumes that your source has the same frame size as what you are encoding to. In those cases, "frame controls" has no noticeable benefit, since it's algorithms neither resize, deinterlace nor estimate motion between frames.

2nd or 3rd tab for frame controls. Turn that on, set the resize filter to "best". Do a short test and compare. Great if you have graphics with diagonal sharp jaggy edges, or a perfect curve with a hard edge. Aliasing is almost always an issue with down conversion.

Depending on your set up, your rendering time will definitely double or quadruple or worse (on a dual G5, with both cores on, it takes me maybe slightly over an hour to get 10+ minutes out to H.264, it estimated 13 hours for the same amount of video). So it's a massive trade off for quality.



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Hi Casey,

Here is another way to do this.

[www.kenstone.net]

--ken

Thanks Ken,

Actually, I've seen that already and tried it, and I'm still seeing the same quality issues.

One time I was trying to make a motion DVD menu using FCP, and I made it in HDV, exported to ProRes, did Compressor with the highest quality DVD settings, and it did the same thing as if I had come directly off the timeline into Compressor.

I tried making it into a 2 minute loop and was going to put it down to tape and do my usual DVD Recorder trick. I did 2 minutes so it would be very unlikely to see the seam, since I wasn't going to be able to get frame accurate. It looked better, but for some reason, I kept getting a white frame every time I went to the menu. I'd be playing the video, hit the menu button, the screen would flash white and go to my motion menu. This was unacceptable, so I had to use the Compressor version. I had a HD Jumpback background with a logo over it. The logo was a little small oval centered on top of the screen.

I used this same background and logo in the full length video I produced, and I can see the difference between the two, but it was the best I could get.

The acid test for any form of codecs, is always a differential matte. It will be hard to judge as mpeg2 is a very lossy codec, so you will see a lot of white spots on the same frame when you compare it with the original off the timeline, but do this...

Drop a few short clips, keep it under 30 seconds (graphics with hard edges, extremely quick movement, flashes, blur dissolves, steep luma/chroma gradients, fairly saturated colors, etc... and one or two shots from the usual HDV codec that you use) on a ProResHQ timeline, set your render to 32 bit float (apple 0 for sequence settings, high precision YUV). Export a self contained QT. Drop that in Compressor, with your usual settings, turn on frame controls, resize filter to best.

Then pump out those clips onto a DVD on your set top recorder. Demux that with Mpeg Streamclip.

You could also run a 3rd test and run that through Compressor with Frame Controls off.

Then open both up in Quicktime, export tga stills of selected shots at around the same frame, and examine them closely. Similar shots should be fairly easy to find if you kept your video short.

Quick transitions and blur dissolves are hard to encode to GOP formats, so you may see pixelation. Aliens should show up with extremely hard, contrasty lines. Gradients result in banding. Colors may mush and bleed after generational loss.



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