CompuServe Messages

Vincent: Thanks for the correction on the P-frames. I was trying to keep it too simply. I have a question for you or anyone else. MPEG and M-JPEG are both based on the JPEG spec. I know it is simplistic to say the M-JPEG captures 30 JPEG frames per second and MPEG captures JPEG frames on I-frames. But can anyone tell me in more technical terms what the difference is between a M-JPEG stream and an I-frame only MPEG stream? and why, if they are both based on JPEG, can't any of the professional editing systems (AVID, DT, etc.) compress to I-frame only MPEG rather than M-JPEG for recompression later to an MPEG file? That does mean writing a new compression algorithm, which is the business reason why no one has done it. But is there a technical reason? It would seem to me someone would do well to create such an "I-MPEG" stream, edit with that, than recompress to lower the data rate by adding the B- & P-frames. Wouldn't such a stream have the advantage of not making MPEG artifacts on top of M-JPEG artifacts? Vincent, BTW, I did much of the testing for the New Media article you mentioned. Jeff Sauer Desktop Video Group