Macromedia's New Alternative to Sorenson Encoding
One of the most interesting part of the SWF specs has been the embedded video section. As you may know, starting with Flash 6.0, Macromedia added support for embedded video inside of SWF movies. The video compression codec was licensed from Sorenson and output to a slightly modified version of the H.263 video compression standard. Although it hasn't gotten any coverage yet that I have seen, in Flash 7.0 / MX 2004, Macromedia has added support for another video codec: ScreenVideo. ScreenVideo basically just divides your screen up into a grid and then encodes each of those grid squares as a lossless (or ZLIB compressed) chunk of data. If a grid square does not change, then the chunk's data is left out in subsequent frames, which means that this format is great for encoding video that has relatively static content (screen recording is a likely usage). Unfortunately, true to Macromedia's style, the docs on the video tags inside the SWF are incorrect (yes, the specs are a ton better, but still a few bloopers in there), and I had to spend all night decompiling SWFs and finally get in touch with Burak (the ASV guy) to confirm my findings. In any case, just to document this so people running into the same prob can find the answer, the ScreenVideo packet needs to be proceeded by UB[4] Frame Type, UB[4] Codec. This bears a striking resemblence to its format inside of an FLV file, which is noted in the specs as UB[4] Codec, UB[4] Frame Type. However, Burak mentioned that the FLV specs might be incorrect and that the reverse order is actually what you want. Oh, well. It works now.