paul@frcs.UUCP (Paul Nash) (01/27/91)
I need as much information as I can lay my hands on about video and audio compression. I am involved in a project to compress TV-quality video and speech-quality audio for broadcast transmission on comparitively slow-speed (9600 - 19200 bps) digital links. Ideally, I would like to find a set of algorithms that I can implement in software, with the option of adding hardware compressor/decompressor boards to gain speed at those sites where speed is important. For those sites where the users are happy about a delay, the software should use a compatible algorithm. The head-end station would probably use hardware compression from the outset, if hardware and software are compatible. I realise that different techniques would be required for video and audio. Please feel free to respond about either or both, if you have any ideas (including tricks for audio modulation, perhaps). Unfortunately, our newsfeed is erratic at times, and I don't get all the groups that I have cross-posted to. Please reply by mail, and I will summarise to the above groups if there is much information and any interest. ---=---=---=---=---=---=---=---=---=---=---=---=---=---=---=---=---=--- Paul Nash Flagship Wide Area Networks (Pty) Ltd paul@frcs.UUCP ...!uunet!ddsw1!proxima!frcs!paul
doug@eris.berkeley.edu (Doug Merritt) (01/30/91)
In article <331@frcs.UUCP> paul@frcs.UUCP (Paul Nash) writes: > >I need as much information as I can lay my hands on about video >and audio compression. [...] >Unfortunately, our newsfeed is erratic at times [...] Well, mail didn't get through to you, either, so I'm posting my reply: The fairly new method of DCT (discrete cosine transform) video compression will probably interest you. There are apparently both lossless and lossy forms, and it is the basis for the new (or under-development?) and famous JPEG video compression standard. I know very little about it (although I intend to learn more), but some useful information: 1) There's a theoretical math book on the subject, titled "Discrete Cosine Transforms". Sorry, I haven't seen the contents, just spotted it in a university book store in the math section. 2) There's some free software that performs DCT's in various ways (JPEG and otherwise, "fast" and otherwise), available via anonymous ftp from think.com, in subdirectories of /jpeg. This is probably your best bet, since it seems to represent good work by members of some kind of mailing list or working group on the subject, and DCT & JPEG are apparently state-of-the-art. I just discovered this archive a few hours ago, so I haven't had a chance to try any of it out yet. I have reason to think that similar methods may be effective for audio, but since I haven't "done my homework" on the subject yet, I'm not positive. By all means, please summarize everything you learn about for the net. Thanks, Doug -- Doug Merritt doug@eris.berkeley.edu (ucbvax!eris!doug) or uunet.uu.net!crossck!dougm