[jip]

1. create an mp3 with id3 tag and correct length (file.mp3)
2. upload file.mp3 to ipod with ephpod/xplay/whatever
3. hexedit the ipod iTunesDB file (x:\iPod_Control\iTunes\iTunesDB): look near end of the file and find the bytes that specify the location of the mp3 you just uploaded. note the location of the file, and modify iTunesDB to point to file.mp4 instead of file.mp3
4. use aacenc_mpeg4 to encode file.wav to file.aac
5. use version 0.9.7.x of mp4tools (mpeg4ip server utils) to put file.aac into an mpeg4 container: file.mp4. it is important to use this version (edit: MP4UI based on this older version of mp4tools, also works)
6. copy file.mp4 file to the ipod, in the directory location you noted earlier (will be somewhere in x:\iPod_Control\Music), and delete file.mp3 that will be in the same directory.

the specification for ADTS headers in AAC has recently changed, but only for MPEG4-AAC (MPEG2-AAC remains the same). version 0.9.8 of mp4tools won't work with the MPEG4-AAC files created from aacenc_mpeg4, since the output has the old format MPEG4-AAC ADTS header, and is 'no longer compliant'. itunes/ipod needs the AAC to contain an MPEG4-AAC ADTS header, and are quite happy with the old ADTS header format. so if you're going to use aacenc_mpeg4, the psytel encoder, it's necessary to use an older version of mp4tools to create the mp4 container. you can use faac (with the "-m 4" option) instead of aacenc_mpeg4, and use mp4tools 0.9.8, but the encoding quality is not as good. a new version of mp4tools is expected to come out that will be able to take aacenc encoded AAC and convert the MPEG2-AAC ADTS headers into MPEG4-AAC for you (as it muxes into the container). itunes/ipod may work with raw (no header) AAC in an mp4 container, but i've not tested that yet. mp4tools seems to have a problem with raw AAC anyway. note that itunes/ipod requires the AAC to be inside an mp4 container.

a great information site on audio coding is http://audiocoding.com/wiki/. you can also find links to software downloads here.

note that aacenc_mpeg4 seems relatively hard to get hold of, let me know if you need it.

p.s. i did a quick comparison of LAME (highest quality VBR) and 320Kbps psytel on my ipod + ety 4s, and the AAC is remarkably better.

 

[blessingx]

Thanks for the info.

 

[austonia]

damn, that's a real pain in the ass. hopefully someone will code a utility to make that easier. ephpod support would be awesome.

 

[richard]

I use essentially the same technique, with psytel 2.15 and mp4ui. Works fine, other than that it's a pain.

ephpod and dbpoweramp should be coming out with versions that support aac (or mp4/m4a) sometime soon

a new version of mp4creator is also supposed to be out soon, so you can use the latest psytel encoder.

aacenc -normal appears to be at least as good as lame -aps, but I need more testing. 320 seems like overkill.

you also need to update ipod to 1.3 firmware. a PC hack is available.

www.hydrogenaudio.com is another good resource

 

[jaskin]

Yeah, I didn't understand alot of what jip said above. It seems quite complicated and I'm hoping Ephpod would support AAC soon

 

[paulj]

The dbPower Amp author says he has a beta plugin that will transfer any file to the iPod. His post is over on HydrogenAudio somewhere.

 

[williamgoody]

Quote:

Originally posted by paulj The dbPower Amp author says he has a beta plugin that will transfer any file to the iPod. His post is over on HydrogenAudio somewhere.

And it works, incredibly well. To my ears AAC at 192kbps is comparible to an MP3 at 320. Incredibly close.

 

[jaskin]

William do you have the link to the program at Hydrogen audio?

 

[blessingx]

Quote:

Originally posted by jaskin William do you have the link to the program at Hydrogen audio?

Try this.

 

[williamgoody]

Quote:

Originally posted by blessingx Try this.

Yep, that's the one.

 

[jaskin]

Thanks guys, I still have alot to learn about audio compression

 

[blessingx]

Quote:

Originally posted by jaskin Thanks guys, I still have alot to learn about audio compression

It doesn't get much worse than this (unsupported compression formats and proprietary hardware). This is all experimental. Just spend a couple hours browsing Hydrogen Audios general MP3 and AAC (and others if you're curious) forums for the more normal stuff.