HydrogenAudio

Lossy Audio Compression => AAC => AAC - Tech => Topic started by: Alexander Ostuni on 2015-03-05 16:39:19

Title: M4a fles from iTunes not gaples with gonemad music player
Post by: Alexander Ostuni on 2015-03-05 16:39:19
Hi,
my favourite Android Player is gonemad music player, as it does everything exactly the way I want it.
I only have one problem with it.
I have bought some allbums at the iTunes store. These are aac files with the ending m4a. These are not played gapless without glitches and cut the very beginning of the songs.
The dev of gonemad wrote me

"at some point itunes stopped properly writing the gapless tags to its  mp3 files (and i assumed they did the same to m4a).  i know exactly what  they are doing but GMMP's audioengine is coded to handle correct values  for the encoder delay and the zero padding at the end.  Apple decided  to add an additional number into their values before writing to the tags  making the encoder delay tag not just the encoder delay, but also  another delay which throws off gmmp's calculations and it will end up  cutting too much.  This is not going to be looked at until 2.1 with all  the other audioengine work that is planned

properly tagged m4a is gapless.. i dont know at what point itunes started doing this"


My question: can I somehow fix these files without transcoding them ?

Cheers
Alex
Title: M4a fles from iTunes not gaples with gonemad music player
Post by: kode54 on 2015-03-06 00:39:33
Somebody needs to read further into the iTunSMPB field and how it works. There is at least one topic on the subject of iTunSMPB (http://www.hydrogenaud.io/forums/index.php?showtopic=87847) on this forum, which may be useful. That applies to MP3 as well, as they use COMM frames with the description of "iTunSMPB" that contains similar fields.

Total samples in original stream, encoder delay, and padding which includes the decoder delay.
Title: M4a fles from iTunes not gaples with gonemad music player
Post by: nu774 on 2015-03-06 03:38:39
"at some point itunes stopped properly writing the gapless tags to its  mp3 files (and i assumed they did the same to m4a).  i know exactly what  they are doing but GMMP's audioengine is coded to handle correct values  for the encoder delay and the zero padding at the end.  Apple decided  to add an additional number into their values before writing to the tags  making the encoder delay tag not just the encoder delay, but also  another delay which throws off gmmp's calculations and it will end up  cutting too much.

I've never heard of it, but if it is true, then everything other than Apple's new products should not be able to play your files gaplessly.
If, for example, fb2k can play your files fine, then it is bullshit.
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