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- Categorized in: Choosing a camcorder
As before, I used presets in Carbon Coder to produce the four files in the three formats, then loaded them into Premiere Pro for snapshots. After testing about four different clips, the nickel dropped, and I reached the rather obvious conclusion that all three formats at the format specific data rates were very artifact-resistant; otherwise, the vendors wouldn’t have used them.
Figure 3. Comparing the formats in interlaced mode. Click here for a larger image
To put this quality in a bit of perspective, at 24Mbps and 1920x1080 resolution, AVCHD devotes about .385 bits of data per pixel. By comparison, a 720p streaming file encoded with the same H.264 codec might have a data rate of 2Mbps, which is .0723 bits per pixel. This is a long way of saying that not only are the compression technologies used in these formats very advanced, the data rates are very generous compared to other common uses. That’s why these cameras produce such stunning (and affordable) HD quality.
The clip that showed the most obvious quality difference was an underwater clip shot by Kenneth Corben. Here, after zooming each clip to 300 percent and comparing them side-by-side, HDV showed the most macro-blocks and mosquitoes surrounding the moving objects, but these really wasn’t obvious at full frame playback. DVCPRO HD was the most block-resistant of the three formats, showing the least artifacts.
Along the way, I also noted that the depth-of-field performance of the Red One should make it a dream for shooting for streaming. For example, Figure 4 shows the milk girls clip that I downloaded from the Red website. Even at 5Mbps, about 20 percent the data rate of AVCHD, the clip was virtually artifact free because so little of the image was in focus. Now that I know that the workflow isn’t horrendous, it might be time to start begging for a Red camera for testing for this purpose.
Anyway, back to our format comparison. By this point, I had reached the conclusion that DVCPRO HD offered slightly higher quality than AVCHD and HDV, though at four times the data rate, it obviously comes with its own set of storage related issues. Still, this conclusion helped shift the focus to a two-horse race between full resolution AVCHD and HDV.
With DVCPRO HD out of the picture, I could start encoding my files progressively and start dialing down the data rate to make the MPEG-2 that fuels HDV and the H.264 behind AVCHD start feeling some pain. My rational was that I could keep downloading and encoding files from the Internet all day and still not see a significant difference at each format's full encoding parameters. However, by reducing the data rate, I could simulate the performance of the respective formats when shooting particularly challenging footage, as well as clear up an internal debate as to the superiority of H.264 over MPEG-2.
Figure 5. At the same data rate, HDV shows macro-block artifacts while AVCHD is smooth and clear. Click here for a larger image
Accordingly, I produced two videos at 5Mbps using MPEG-2 at 1440x1080x24fps and H.264 at 1920x1080x24fps: Michael Hastings’ great shot of the space shuttle launch (see Figure 5) and the second the Corben clip shown in Figures 3 and 6. In the first clip, HDV shows significant blockiness as the camera tilts upward following the space shuttle, while AVCHD remains clear.
In the second clip, HDV again shows severe blockiness. AVCHD looks a bit smudged, while remaining clearly preferable to its MPEG-2 based competitor. This is particularly interesting because although I produced the AVCHD clip at full resolution (1920x1080) and the HDV clip at 1440x1080, the per-pixel bit rate of the HDV clip was 25 percent higher.
The bottom line is that a full-resolution AVCHD camera should produce better video than an HDV camera because the underlying compression format is superior. Every camera is different, of course, and optics play an obviously major role, but if all other factors are equal, AVCHD should do better.
One final shout-out. As late as I was on this project, I would still be working right now if not for the stunning performance of the eight-core HP xw8400 workstation I use as my primary workstation. At one point, I had RedCine converting 4K footage to QuickTime and Carbon Coder batch-encoding multiple HD clips, and I expected to see smoke coming from the machine. But like the proverbial Energizer bunny, it kept going and going. If you’re working with HD footage—affordable or not—you’re going to need an eight-core system.
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