If it looks good, I lower the bit rate 100 kbps. When I create a test compression, if the compressed movie looks bad, I raise the bit rate 100 kbps. NOTE: The general rule is that if you don’t see blocky artifacts when the video is enlarged 2x, then the artifacts aren’t there.Ĭompressor displays the total duration between the In and the Out in the lower right corner of the Preview window. The compression won’t take a long, and this provides a long enough playback that you can study it for artifacts. A good test is to compress 5 to 10 seconds of the video. Then, move the playhead to the end of the movement section. Position the playhead in the Preview window where a section of typical movement starts and either drag the In marker from the left edge of the mini-timeline, or type “ I“. To create a short test movie in Apple Compressor, import the file you want to compress into Compressor. NOTE: This process is the same for both Compressor 3 and Compressor 4. This article shows you how to do this yourself. The problem is that neither Apple Compressor nor Adobe Media Encoder has a: “Create Test Movie” button. (Still frames and locked-down landscape shots compress to virtually nothing and are not a good test for compression.) If you can compress movement without artifacts, you can successfully compress the entire movie. Use the part where your actors and/or camera are moving and you want to make sure all the detail in the image is retained. You may have a swish-pan for which detail is not important. To save time, before compressing an entire movie, select a short – 5 to 10 second – section of your movie that has the most movement for which you want to retain detail. But video compression can take hours only to discover that everything we compressed is wrong. If video compression was instantaneous – like saving a PDF of a word processing document – when we saw artifacts, we’d just tweak the bit rate and save it again. But, my video podcast “2 Reel Guys,” which has the same frame size and frame rate, but MUCH more movement, can’t be compressed much lower than about 2,000 kbps. Compression settings always need tweaking. For instance, I’m able to compress my online webinars to about 400 kbps. There is no single bit rate that consistently yields the smallest file size with the highest possible quality. We care because every movie is different. Now, all the artifacting has disappeared because the bit rate is high enough to support individual pixel detail. Here’s the same image, but compressed with a higher bit rate. These “superblocks,” as they are called, can be compressed to fit very small bit rates, but with a significant loss of detail. The reason these exist is that, as a fall-back, codecs compress pixels in blocks when the bandwidth is too low to support compressing individual pixels. See all the weird rectangles, ragged edges, and blurry detail? Those are artifacts. Here’s the same detail after compressing with a bit rate that was too low to support the frame size, frame rate, and, most importantly, the amount of movement between frames. This is taken directly from the video itself, fully uncompressed. Here’s a detail from a clip about a Chinese Dragon dance. When the compression bit rate is too low for the frame size, frame rate and/or motion in the video, you get artifacting.
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