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FS#12661 - Problems when playing m4a files

Attached to Project: Rockbox
Opened by Wolfgang Dilg (rasferret) - Thursday, 03 May 2012, 12:32 GMT
Last edited by MichaelGiacomelli (saratoga) - Thursday, 03 May 2012, 18:35 GMT
Task Type Bugs
Category Music playback
Status Closed
Assigned To No-one
Operating System Sansa AMSv2
Severity Low
Priority Normal
Reported Version Daily build (which?)
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 0
Private No

Details

I have prolems playing m4a files on my clip+.

1. all m4a files available at
http://metaebene.me/podcasts/
e.g.
http://meta.metaebene.me/media/mm/mm086-deutschland-wurde-heruntergeladen.m4a
won't work. They playback engine just skips the files.

2. playing files available at
http://www.apfelklatsch.de
e.g.
http://files.apfelklatsch.de/podcasts_m4a/apfelklatsch_ak_032.m4a
consume a enormous amount of cpu time when being played higher speed. normally I listen to them at 180%. with the dev build 5f0cb7 at this speed there apear clicks while playback.

This task depends upon

Closed by  MichaelGiacomelli (saratoga)
Thursday, 03 May 2012, 18:35 GMT
Reason for closing:  Not a Bug
Additional comments about closing:  See comments.
Comment by MichaelGiacomelli (saratoga) - Thursday, 03 May 2012, 18:27 GMT
For 1), the problem is that AAC-HE files use a lot of memory, and they use even more memory when they're several hours long. For that kind of file you're probably going to be limited to about 1.5-2 hours of length before the Clip+ runs out of RAM and skips the file.

For 2), the problem is that AAC-HE files use a lot of CPU power to decode, which is fine normally, but if you run them at 2x speed they also need 2x the CPU power. Factoring in the overhead for the pitch correction and such, you'll probably be limited to about 1.5x speed if you want realtime playback (that is, no skips).

Both of these problems might in principle be fixable with enough clever optimization and memory savings, but they may not be as well. Either way, they're not bugs, just limitations of what the rather limited hardware can do with such an excessively complicated format as AAC-HE.

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