bpa wrote: > Good. > > > This is long explanation and my understanding but it may have > inaccuracies > > MEPG-4 is a flexible but complex transport format so there are many ways > of laying out data in a file - an MPEG4 file is made up of data "atoms". > If a file is played by an application which has access to the file > (e.g. a PMP) then the application can jump anywhere in the file (e.g. > beginning , middle or end) without a problem. A streaming player can > only play a file from beginning to end - it cannot jump to end of file > as file is streamed from first byte to last. > > AAC audio is organised in frames. The start of each frame has to be > identified. In ADTS format (mainly used by HTTP AAC streams) this is > done by a special byte sequence at start of each frame. In MPEG4 > format, there is an index table with byte offset pointers for each > frame. When ffmpeg is converting a file to create an MPEG-4 AAC file, > it builds the index table internally but outputs the audio data as it is > processed in the "mdat" atom. When all the input file is process, ffmpeg > then write the index table (and other data) at the end of the file in a > "moov" atom. A file based player can play this file because it can > easily jump to end of file to the index, fetch the index and then jump > back to start of file and find the audio frames to be played. A > streaming player gets the audio first, doesn't know where the frames > begin and so halts. > > The "-movflags faststart" option make ffmpeg do a second pass on > converted file and move the audio data to end of the file so that a > streaming player gets and reads the index table first and then when > audio data arrives next, the streaming player knows where the frames > begin. > > Other data such as embedded cover art could also be positioned at the > end and this may cause problems to a streaming player.
Thank you for all of your assistance and knowledge! I'm happily listening to my m4a files on this new build :cool: ------------------------------------------------------------------------ Eric0321's Profile: http://forums.slimdevices.com/member.php?userid=68013 View this thread: http://forums.slimdevices.com/showthread.php?t=108852 _______________________________________________ unix mailing list unix@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/unix
