Shooting for Streaming, Part 4
The best deinterlacing tool I’ve ever used is in a product called AlgoSuite produced by Algolith (www.algolith.com). It’s expensive and slow, but could prove invaluable if you’ve got problematic interlaced source video to convert to streaming. Obviously, the better the deinterlacing tool, the less difference there will be between interlaced and progressive source video. If you’re using AlgoSuite or a similar tool already, expect fewer quality benefits from switching to a progressive-source camcorder, though not having to pre-process your video through AlgoSuite would save tons of time. For these tests, I deinterlaced in Adobe Premiere Pro.
When Interlacing Artifacts Are Noticeable in the Final Stream
The image of my golf swing shot at a shutter speed of 1/2000 is the original uncompressed video, straight from the Premiere Pro timeline. When will the artifacts be most notable in the compressed stream?
Well, obviously, if you distribute the video at 160x120, at 28.8Kbps, changing from an interlaced to progressive camcorder will make little (if any) difference. On the other hand, at the rough parameters that ESPN uses (440x330 at about 600Kbps), the difference is clearly visible.
The interlaced source clip is a bit fuzzier than the progressive image, in part because of deinterlacing and in part because I had to apply more zoom to make it equal to the size of the progressive image. That said, the jaggies on the club are all deinterlacing artifacts, and the club on the right is much clearer. Moreover, you also notice slight jaggies throughout the image, on the sweater, in the neckline, and on the arms.
Overall, it takes the confluence of factors to actually see the benefit of shooting in progressive mode as opposed to interlaced. That is, you need high-motion video with sharp detail shot at a very high shutter speed, along with video delivered at a resolution large enough and data rate high enough to show off and preserve the quality differences.
With this as background, let’s walk through my test scenarios and view the results. In the case of the high-motion videos, I’ll identify the shutter speed tipping point where interlaced mode produces similar results to progressive. In addition, the final test revealed a completely different set of circumstances where progressive video totally outshined interlaced.
Office Environment
The first test emulates the carefully crafted streaming environment with a dark background, flat lighting, and minimal detail. The shot is a medium close-up, chest and higher, with minimal room for arm waving. In this and all subsequent tests, I shot in interlaced mode with the Sony HDR-FX1, while shooting in progressive mode with the Canon XH A1. I shot all these tests in DV mode, some in 16:9 and some in 4:3, eschewing HDV because the XH A1 has higher-resolution CCDs than the FX1, and produces better high-def images. At DV resolutions, captured video quality was virtually identical, focusing the test on the format differences, rather than the qualitative differences between the cameras themselves.
For these indoor shots, I disabled gain, set shutter speed at 1/60, and adjusted aperture and/or lighting until exposure on the face was optimal, using the waveform monitor in Adobe's DV Rack (now called OnLocation) as a guide. I used single-key lighting with a backlight for this and the next shoot, and with 1,000 watts shining down from behind the camcorders, both were at or near the lowest available aperture. I perhaps could have boosted shutter speed to 1/100 without darkening the image, but no further.
As with all the videos I produced for this article, I output the two files, side by side, using multiple codecs, including Flash, Windows Media, and QuickTime, and multiple resolutions, including 640x480, 440x330, and 320x240. None of the videos in this test run showed any noticeable difference in quality between the progressive and interlaced source.
Analyzing the source video and shooting parameters, this isn’t really surprising. There’s very low motion due to the tight framing, no sharp detail like the shaft of a golf club, and the shutter speed was relatively slow, dulling the minimal detail in the shot. After viewing these results, I wondered whether shooting a medium shot with increased motion would make a difference—the John Madden/Dick Vitale scenario. Specifically, does the result change if you have a highly energetic speaker shot in a medium shot to make room for the motion?