On Sat, 2003-03-15 at 04:29, Matthias Riese wrote: > Florin Andrei <[EMAIL PROTECTED]> writes: > > > > Proof: rip any DVD you like, and look at the total size of the VOBs. Is > > that smaller than 4.7GB? Then it'll fit into a recordable DVD. Is it not > > smaller? Then it needs re-encoding. > > Quite often you'll still have to re-encode it to a lower video bitrate > > to make it fit. And that's _very_ slow. > > Not necessarily. For example > "9to5 DVD-Ripper" from Buhl Data > DVD2One from Erwin van den Berg > InstantCopy from Pinnacle > (all commercial and for Windows only AFAIK) can reduce the size of a > DVD very quickly. According to a friend of mine they do so by > repeating only the steps of the MPEG encoding necessary to achieve > lower bitrates while re-encoding. He said this optimization would be > very obvious and easy to implement (well, he has specialized in video
Ah, yes, that's doable as long as you don't necessarily want to go through uncompressed RGB/YUV as an intermediate step (like transcode and some other tools do). If you keep the stream in MPEG2 all along, and just tweak some bits and pieces, it should be fast indeed. There may be an added advantage to that: the quality loss would be a lot smaller. Going MPEG --> YUV --> MPEG is certain to add some nasty artifacts (well, ok, if you end up with the same format with which you started from, the generation loss is signifficantly smaller than when going from one format to another, like MPEG2 --> YUV --> DivX), especially if you use the exact same codec all the time, but there still is some generation loss nevertheless. That reminds me of a tool i've seen some while ago (was it on Freshmeat?) that claimed to perform "lossless" JPEG transformations, such as rescale, etc. The documentation said that the tool didn't convert back and forth to/from uncompressed bitmap, but kept everything all along in JPEG, hence the losses, if any, were reduced to the theoretical minimum. But now i see, thanks to your comment, that another advantage might be speed improvement. I guess it's up to the MPEG codecs to perform the magic, and if there is indeed such a capability, the tools relying on them should support that (i.e.: don't break down the stream into YUV, just pass it to the codec, let it do the tweaks, and get it back again in MPEG). Well, i'm not an expert in MPEG codecs, so i could be wrong, of course. -- Florin Andrei http://florin.myip.org/ ------------------------------------------------------- This SF.net email is sponsored by:Crypto Challenge is now open! Get cracking and register here for some mind boggling fun and the chance of winning an Apple iPod: http://ads.sourceforge.net/cgi-bin/redirect.pl?thaw0031en _______________________________________________ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
