Can I transcode between DV and motion-JPEG, MPEG-2, or DV50?
You can. Depending on the amount of compression used, you might not even see a difference. It seems to be generally accepted that M-JPEG compression at 3:1 is roughly equivalent in quality to DV’s 5:1 compression. It’s also worth remembering that DV and JPEG are both DCT (Discrete Cosine Transform) codecs; they tend to have similar artifacts and effects on pictures. (DV gets its additional compressive efficiency through block-level optimization of quantizing tables, whereas JPEG uses a fixed quantizing table for an entire image). Thus, one might venture to guess that whether one is compressing via 5:1 DV or 3:1 JPEG, similar amounts of damage are done to the image, and that transcoding between these two compression schemes might cause less degradation than the initial compression caused. Indeed, at NAB ’96 Panasonic had hidden away in a corner a most interesting demonstration. A D-5 (uncompressed ITU-R-601) signal was fed to a component digital switcher on input #1. It was also taken,
