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Aliasing trouble with AVCHD / DVDSP workflow

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John Baldino
Aliasing trouble with AVCHD / DVDSP workflow
on Apr 14, 2010 at 7:40:31 am

Hi guys,

I know this has been covered somewhat already but rather than spend three hours piecing together various threads I thought I'd consolidate my issue into one new post.

I am just now testing out HMC-150 to DVDSP workflow as I had a small gig for a client today and have to deliver DVDs tomorrow. My issue is that I am getting very noticeable and undesirable aliasing/general suckiness during playback of the DVDs on a standard DVD player hooked up to a rear-projection HDTV using component cables. The audio is fine, but the video quality just isn't what it should be.

The footage is extremely simple...just choirs singing and standing in once place. No editing, in-camera fades, and simple menu. The workflow I'v been using is this:

-Acquire AVCHD in 720/30p over SDHC
-Log and Transfer (transcode) AVCHD files w/ FCP
-Import newly created .mov files to DVDSP
-Assing assets to menu, encode with 1-pass CBR @ 6 mb/s

I should add that I've experimented with using both 1 and 2 pass VBR as well as different settings for "motion estimation". Same results.

I know the obvious thing to do next is to go through compressor, but it seems as though I shouldn't have to. Also, because I am on an extremely tight deadline, I don't have time to let the footage encode all night. If I had the luxury of time I probably would have experimented with going to compressor first and using the 'best' quality DVD settings, but aside from the fact that it would probably take longer to encode (time that I dont' have with this project), something tells me that there is another problem I need to address.

Here are two still frame exports to show what I'm talking about...the first is from the 720/30p ProRes 422 file, the 2nd is the same frame on the DVD:

Original Frame

Same frame on the DVD

Anyone have any thoughts/ideas?

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John Baldino
Re: Aliasing trouble with AVCHD / DVDSP workflow
on Apr 14, 2010 at 9:46:12 am

I partially answered my own question. I went through compressor this time and then imported the m2v file and ac3 into dvdsp and i had no issues with quality this time.

After doing further research I found out that the original problem I had with encoding in DVDSP might have had something to do with not setting the correct field order (upper vs lower). I am reading on some threads that AVCHD uses upper whereas DVDSP defaults to lower? Anyone else know about this?

If this is true about the field order being responsible for why I was getting such a lousy transcode from DVDSP, I'm still a little curious about why compressor didn't give me any issues...both settings for both encoders was set to "auto" for field both DVDSP and compressor. My thinking at this point is that maybe compressor is better at analyzing the source file and correctly chose upper field whereas DVDSP did not?

oh the complexities...

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