Mp4 isn't gapless too?
Reply #7 – 2003-03-03 10:17:14
Take a look at this thread : http://www.hydrogenaudio.org/forums/index....91&hl=minkowski Or at this one: http://www.audiocoding.com/phorum/read.php...f=1&i=744&t=743 So this question is at least more than one year old, and Menno did not follow that idea he mentioned there yet. Maybe because this feature wasn't questioned by other users or perhaps because he found difficulties with that "hacker" approach afterwards.* As I mentioned in the other thread, the proper "gaplessness" of any content in the MPEG-4 standard is probably handled by the Scene Description (BIFS) which is a binary stream itself within the MP4 container besides other elementary streams like audio or video content. As long as an AAC encoder does not provide these Scene Descriptions in a MP4 container, there's of course no chance for a MP4 decoder to use them (the field "BIFS" can already be seen in a MP4 header though). I don't know what QuickTime 6 Pro does when you encode a MP4 "movie" with it, but maybe there are already solutions for this problem, because Apple/QuickTime is also exploring the MPEG-4 possibilities for streaming live content over the internet, and there you'll certainly need an answer to this "gapless" question. The MPEG4IP project does the same, so maybe a MPEG-4 compatible solution could also come from them. *Edit: OK, here's the reason why MPEG-2 AAC can't be gapless in the normal sense of the term (only full blocks of 1024 samples are possible during encoding):http://www.hydrogenaudio.org/forums/index....=ST&f=13&t=2285 This also explains why sometimes you get better results (when a file length comes close to this limit) and sometimes you don't with usual players and/or additional "gapless" plugins. This is also due to the ADTS or ADIF headers that have to precede every frame or at least the beginning of a new file in a MPEG-2 AAC bitstream. In the MP4 container those headers are gone (= raw AAC bitstream), and the additional side information (like "subtracks" of a long file without gaps) is supposed to be handled by the Scene Description.