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MillimeterShooting for Streaming, Part 2
Aug 25, 2008 12:00 PM, By Jan Ozer
Other Encoding Tools
Before finalizing my conclusion about whether it was better to shoot in HD or SD for sub-SD resolution streaming, I wanted to encode the DV and HDV footage in a third-party encoder and compare the results. Because Sorenson Media Squeeze is a relatively inexpensive cross-platform solution, it seemed like the best alternative.
However, I had edited both source videos in Premiere Pro, trimming, brightening a bit and (sigh) color-correcting the source. So now I needed to export an intermediate file from Premiere Pro to import into Squeeze. In general, when producing an intermediate file from an editor, you have two high-level choices.
First, you can render a file at the resolution of the original acquisition format, which forces the third-party encoder to scale and often de-interlace the video to its final resolution when producing the streaming file. Alternatively, you can render the intermediate file at your target resolution, letting the NLE scale and de-interlace, and simply encode in the third-party encoder. Normally, I use the latter alternative, but because scaling quality seemed to be the crux of my comparison, I used the former method to force Squeeze to scale and output both files. Within Premiere, I kept the files at their original native resolutions (using the DV preset for this operation for the SD video, rather than the 640x360 preset).
With either alternative, you have to choose a format for storing the video. One alternative is to simply store the file in its original acquisition format (HDV if HDV, DV if DV)—which is simple, but not best practice because the NLE will have to re-compress the video if you’ve made any global change such as the brightening and color correction that I had performed. Better to use a lossless or less lossy format.
When choosing an intermediate format, you have several considerations. First is the length of the video file itself, which can impose some practical limitations. If you’re working with a full-length movie, using a lossless format such as Apple’s PNG codec or the Lagarith YUV12 codec may not be workable; you may need a lossy format such as Apple’s ProRes 422.
Assuming your video is relatively short, like this one, you can use a codec such as the QuickTime PNG codec, which is great for cross-platform encoding (which I do a lot). Or for Windows-only work, the Lagarith codec is a great choice.
I used to use the Apple Animation codec to produce files for cross-platform encoding until Microsoft’s Ben Waggoner pointed out that this codec was RGB-based, while most origination formats and streaming codecs are based in YUV color space. He (and several other sources that I’ve since read) recommend against this codec because the additional YUV-to-RGB conversion can cause distortion, although I’ve never seen this in practice. Still, at Ben’s suggestion, I’ve starting using the QuickTime PNG codec to produce files compatible on both platforms, and it’s about 50 percent more efficient than the Animation codec with equal quality.
