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MillimeterMPEG-2 Encoders, Part 2
Aug 17, 2010 12:00 PM, By Jan Ozer
Figure 5. MediaInfo telling me that this file produced by BitVice had the correct 24p flag.
24p clips
With the 24p sequence, I was testing both quality and the ability for the encoding tool to produce 24p files that loaded properly into DVD Studio Pro. To explain the latter, if you're shooting in 24p, you want to author your DVDs in 24p—not only to retain the filmic look, but because there are 20 percent fewer frames than there are in a 29.97fps file. This means that you can produce 20 percent better quality at the same data rate as the 29.97fps file, or at a 20 percent lower data rate at the same quality as the 29.97fps file.
Encoded and authored correctly, 24p files play at that rate on devices that can support 24p playback, such as most modern DVD players connected to most modern HDTVs. On the other hand, when these 24p DVDs play on older gear that can't handle 24p playback, the files contain a flag that tells the DVD player to convert the 24p footage to 29.97fps for NTSC-compatible playback.
I could tell when 24p files were encoded correctly when I analyzed them in the ever-useful (and always free) MediaInfo analysis tool and saw the 2:3 Pulldown in the Scan order on the third line from the bottom in Figure 5.
Figure 6. DVD Studio Pro telling me that it didn't like 24p files produced by Squeeze and Episode.
DVD Studio Pro had an equally determinative but somewhat less informative test: If it didn't like the file, it just opened the error message shown in Figure 6.
The only two encoders that produced compliant 24p files were Compressor and BitVice; neither Squeeze or Episode would produce 24p files that DVD Studio Pro would load. (Note that I did get this far with the Cinema Craft files, and they loaded fine in DVD Studio Pro.) Quality-wise, BitVice and Compressor were about even on this test clip.
Where does that leave us? If you have Compressor, and it's working well for you, I wouldn't spend a lot of time trying to boost quality with a third-party program. If you don't have Compressor, or you don't like the program, BitVice would be my first choice for a third-party tool. I should mention that if you've got noisy source footage, BitVice has a highly regarded noise filter that's also worth a try.
Though I'm guessing few producers buy Squeeze for MPEG-2 encoding, it output the lowest quality in my trials—though again, at a data rate of 7.5Mbps, you probably wouldn't notice the difference unless you're working with exceptionally high-motion video. I don't hesitate recommending Squeeze for streaming encoding, but I wouldn't use it to produce my DVDs—particularly those shot at 24p.
As mentioned in the first installment, the next version of Episode will have a new MPEG-2 encoder, and should also produce files with a 24p flag. I might give that a try down the road, but if you're using any version prior to version 6, which will be the new version, you won't be able to produce compliant 24p files, and you should be able to get better quality with Compressor.
Continue the discussion on “Crosstalk” the Millimeter Forum.