ALAC codec incorrect

[jheffernan]

I had a problem with some files I was converting over FLAC to ALAC, (don't ask why ). Most of the files played fine over my Sonos system but some gave me errors. I happen to work at Sonos, so I handed the files over to my developer and he gave me this response:
-------------------------------------------------------------------------

The problem is with the 'stsc' atom.



According to the quicktime file format, the structure should be as follows:

http://tuvix.apple.com/documentation/QuickTime/QTFF/QTFFChap2/chapter_3_section_5.html#//apple_ref/doc/uid/TP40000939-CH204-33068

As you can see, each entry in the sample-to-chunk table is 12 bytes long. The problem with the file is that the size of this atom is 32 bytes, which allows for 2 entries in the sample-to-chunk table, but according to the 'Number of entries' field there is only one entry. Thus, there is an extra bogus entry in the table.



-----------------------------------------------------------------------

Any thoughts on this? I can send the files to anyone that wants them.

Thanks,
Jason

[jheffernan]

Re: ALAC codec incorrect

Please just tell me this makes sense to someone, (Spoon)?

Thanks,
Jason

[Spoon]

Re: ALAC codec incorrect

I will ask my man, who might know...

[jheffernan]

Re: ALAC codec incorrect

Thanks Spoon.

I'm sorry I'm the middle man here, but if need be I can get my developer involved.

Thanks again!

-Jason

[Spoon]

Re: ALAC codec incorrect

Jason please send me an email:

http://www.dbpoweramp.com/email.htm

[jheffernan]

Re: ALAC codec incorrect

Email sent with the forum title as the subject. I apologize for the late reply.

Thanks,
Jason

[spasiba]

Re: ALAC codec incorrect

Hi There,
I just spend hours converting several thousand FLAC files to Apple Lossless so i could play these on my sonos, i ran into the problem that the sonos sees some of the files encoded by dbpoweramp to ALAC as corupt as the above user indicates.

Could you please fix the bug in the code so i can listen to my apple lossless files on my sonos? it would be an easy fix which would save me and many other sonos users alot of headaches.
Please fix this so that the encoded files comply with the quicktime file format.
Thanks!

[spasiba]

Re: ALAC codec incorrect

m4a optimize utility fixed this issue
thank you!

[Spoon]

Re: ALAC codec incorrect

We will endever to fix this issue asap.

[Spoon]

Re: ALAC codec incorrect

Can someone please send one such file which does not play (as small as possible please):

http://www.dbpoweramp.com/email.htm

[charlesw]

Re: ALAC codec incorrect

Spoon,

The Sonos has the problem with _any_ ALAC file produced by the dBpoweramp ALAC encoder.

The fix is to simply run the M4A Optimize codec through the ALAC files (the hint track stuff wasn't enabled). So I guess all that happens from the optimizing is that the tags are moved from the end to the beginning of the file (that was what I could surmise by looking at the files before/after with a hex editor).

I suppose since Sonos is all about streaming, having the tags at the start of the file is important.

[LtData]

Re: ALAC codec incorrect

There is a checkbox to enable the hint track on the r12 version of the encoder.

[Spoon]

Re: ALAC codec incorrect

I still need a file that is wrong, so I can convert it with a new version which might fix the issue, then someone can try on a sonos.

[charlesw]

Re: ALAC codec incorrect

Spoon,

Perhaps I am being unclear.

You can generate a problem file yourself by taking any FLAC file (for example) and converting it to ALAC with the current posted M4A Codec.

Then you can do the same conversion with your updated M4A Codec and compare the output.

I'm not sure I understand why you insist on a ~25mb file being sent to you when you can generate your own with the currently posted codec. Maybe I'm missing something...

LtData, no the hint track checkbox was not checked. I haven't experimented to see if that solves the problem from the start. I don't quite understand what the "hint track" stuff is all about. Perhaps you could please explain its purpose?

Thanks!

[LtData]

Re: ALAC codec incorrect

See here for what a hint track is: http://developer.apple.com/documenta...ection_36.html