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Apple DVD Studio Pro 4DVD authoring moves to HD! Format conversions with advanced image analysis
Beyond the simple capability to encode HD in H.264 or MPEG-2, Compressor 2 adds numerous enhancements to produce great results. These include outstanding scaling features with three algorithm choices: nearest pixel (fast), linear filter (better) and statistical prediction (best and slowest). And it offers four levels of rate conversion quality, allowing you to change the frame rates of your source footage using "nearest frame," "frame blending," "motion compensation" and "high-quality motion compensation." Both of these features allow for things like upscaling SD to HD; downconverting HD to SD; and even converting between NTSC and PAL standards in numerous formats, such as 10- and 8-bit uncompressed, DV, DV50 and DVCPRO HD, among others. (This is obviously welcome news for the numerous DVD authors who work in both standards and need to produce titles in both NTSC and PAL from a single source.) How well does it work? Well, obviously it depends on what you're working with and where you're taking it. These new "optical flow" features (scaling and retiming) are designed primarily for common format/standards conversions, like going from 24 frames per second to 30 frames per second or translating PAL to NTSC (or the other way around). They're not designed to produce miracles (like converting a 2 FPS, thumbnail-sized GIF animation to 1080i/60). Nevertheless, they can produce results that are nearly miraculous.
For example, let's say I have a 720 x 480 sequence running at 24 frames per second, and I want to up the frame rate of this footage to 29.97 FPS. Obviously this means that some extra frames are going to have to be inserted to accomplish this. Now, what will normally happen is that certain frames are simply duplicated to bring the timing up to the desired rate--say, for example, when doing a format conversion out of QuickTime Pro. This doesn't change anything in the sequence of images; it simply adds duplicate frames to achieve the desired rate.
But in Compressor 2, you can actually apply settings that will analyze the existing frames in order to insert new, unique frames where needed. And I don't mean a simple fade between one frame and another. I mean an interpolated frame akin to something you might achieve when tweening frames in a vector-based animation. Except you're not working with vectors here, so Compressor is actually calculating these complex "inbetween" frames to create data where no data existed before. The sequence below, for example, originally consisted on two frames. In order to bring the timing up, an additional frame needed to be inserted. And what you'll see is that this frame has been created as a unique intermediate between the surrounding frames. (Use the slider below the movie to scroll back and forth to compare the original frames with the generated frame. The first and third frames are from the original footage; the second frame is interpolated by Compressor. Note that this footage has been resized and recompressed for the Web, so there's been some loss of quality from the original.)
The results are obviously fantastic (discounting the low quality of the images themselves, which, again, have been recompressed for the Web). But don't expect results that amazing on every single interpolated frame. Though the scene in the example above was complex, most of the moving elements changed very little from frame to frame, so the interpolation came out great. But in scenes where there's fast action, Compressor will sometimes produce more of a "ghosted" inbetween frame, which is to say a frame the looks like the preceding frame overlaid on top of the succeeding frame. It's not a bad thing; it's just not as amazing as the first example. Here's a sample of this second kind of interpolation you might experience. In the example below, frames 2 and 4 are interpolated; frames 1, 3 and 5 are original. Use the slider to compare the frames.)
Note that since there's little change between frames 1 and 3, you see a pretty solid interpolation; between frames 3 and 5, there's more movement, so you see the ghosting effect. And, again, your results will vary based on your source footage and the final output format, and so will the time it takes to perform the interpolation. (We'll get to performance later on.)
New audio capabilities
So those are some of the new features on the visual side. What about audio? There are four significant changes in DVD Studio Pro 4 and Compressor 2 in the area of audio. The first is support for audio files with high bit depth and sample rates--import and export of up to 64-bit (float)/32-bit (integer) 192 kHz linear PCM. The second enhancement is support for importing DTS audio at up to 24-bit, 96 kHz quality, plus DTS ES with up to 6.1 channels. (Note that DTS audio imported into DVD Studio Pro 4 still must use the .cpt file extension. DVD Studio Pro does not include a DTS encoder.) Third, is the addition of the Dolby Digital Professional encoder, which is integrated into Compressor. (Previously Dolby Digital encoding was handled in a separate application called A.Pack.)
And, fourth, DVD Studio Pro's Simulator can now play encoded Dolby Digital and DTS files straight through a G5's built-in digital audio port. In previous versions, Dolby Digital files would be mixed down to stereo for previewing, and DTS files couldn't be previewed at all. So this is a very welcome change. Of course, you must connect your system to a decoder capable of handling DTS or Dolby Digital, but practically every home theater receiver on the market can handle both formats these days, so your options are virtually limitless.
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