M4A files play and pause on ipod nano

[Rooy]

Hi all,
This is on ipod nano, cvs 20061208, no additional patch, WPS is cleardark.
I have some M4A files which are AAC SBR, 44,1kHz, 64KBps, encoded with iTunes v6.0.5, QuickTime 6.5.2 (i read these info from foobar2k). The files are from this torrent, [deleted.  Do not post links to downloads of copyrighted material here.] The author described how he/she created these files under the comment section:
 
``They came split; that is how the tracks were on the source CD. But I've used mpgtxwrap on the Mac to split very long mp3 tracks into smaller chunks. With very long tracks of the sort you get with audio books, I choose the number of chunks to split the long track into so that each chunk comes out at around 3 to 5 minutes. The cuts are not seamless but it's good enough for spoken word recordings.''

 In rockbox, this file (4:57 http://files.myopera.com/Rooy/files/01%20-%20Foreword%2C%20Chapter%201-1_%20A%20Brief%20History%20of%20Relativity.m4a ) shows as 2:28, 128KBps shorten CBR, and plays for 2 secs or so then pause, and continue for 2 secs, etc. Another file http://files.myopera.com/Rooy/files/3-10%20Chapter%205.%20Protecting%20the%20Past%20(continued).m4a doesn't play, and in the playlist has (ERR) in front of its name.

An encoding/transcoding program named Bonkenc ( http://www.bonkenc.org ) has similar problems reading these files.

Looking forwards to a fix soon!  

[michael.conner]

HE-AAC (AAC SBR) files don't play correctly in Rockbox.  From what I've read, they play back at half the sample rate (22050) in the original firmware.

Check out: http://www.hydrogenaudio.org/forums/lofiversion/index.php/t32153.html

[aitwith]

well thank goodness i did a search, as I was just going to post a bug report about this issue  

my HEAAC-SBR encoded m4a's (encoded with nero) also stop and start every few secs. (on ipod nano) I havent updated rockbox to the latest build recently (i think i'm still in november  ) so I'm not sure if this has been fixed at all....
the firmware plays at half the sample rate...do you mean it will actually play half, or it constantly plays at half of the usual sample rate (of 44.1?) would encoding with a sample rate of 22.05 temporarily solve this issue?
I'd love to have this format for my ipod, as its highly compressed, so i can squeeze as much music onto my player as i can, with all my files and stuff!

anyways, I'm here to help test with my files if you need some help   or more information!

thanks for all the excellent work on rockbox!

~ait

[Lear]

SBR decoding isn't optimized in Rockbox, and don't expect a fix soon. One option is to disable it, so that SBR files can be listened to, though without the extra SBR parts.

The "plain AAC" part of an SBR file is often (always?) encoded at a lower sample-rate (in this case, 22 kHz). The SBR decoder then upsamples it. Rockbox currently doesn't handle that fully. It shows the correct sample rate, but the calculation for play time is not correct (for SBR files).

[aitwith]

ah alright. well thanks for taking notice

when you start working on getting SBR to run properly, drop me a line and I'll help with any testing you may need! (unfortunatly, i can't write code for beans I'd like to learn though!)

-ait

[saratoga]

when you start working on getting SBR to run properly, drop me a line and I'll help with any testing you may need! (unfortunatly, i can't write code for beans I'd like to learn though!)

-ait

Not likely to happen.  The CPU on your Nano is almost certainly too slow for SBR, unless someone comes out with a massively faster (and GPL compatible) decoder then any of the current ones.