Is AAC gapless playback working (r3.9.1) ?

[grums]

Sorry if the answer is too obvious, I'm unable to find it:

Just saw release notes of r3.9.1 claiming to fix AAC gapless playback, I installed and tried it: it doesn't seem to work on my Clip+.
Vorbis-encoded files from the same source play gapless OK.

Do I have to prepare the files for neroAAC 1.5.4.0 encoder in any special way, or is there a special/secret tag being used for the encoding?

The files were ripped using EAC instructed to delete leading/trailing silent blocks, but I'm not aware if that actually means silent samples...

[saratoga]

You don't have to do anything to use gapless.  The encoder simply writes the gapless tags, and the decoder uses them to decode the file without adding extra samples.

[grums]

OK - does that mean that the encoder merely instructs the decoder to use gapless playback (if possible)?
Still, in my example: where does the difference in Vorbis and AAC playback come from, when they're encoded from same FLAC file, and supposedly both capable of gapless playback?

[Llorean]

Gapless playback is only used if the encoder knows how to make a gapless file. AAC isn't natively gapless, so it's possible to create AAC files without the proper data to be played back without gaps, while Vorbis is natively gapless so any (non-buggy) encoder will create Vorbis files that will be played gaplessly by Rockbox if they come from gapless source files.

[saratoga]

OK - does that mean that the encoder merely instructs the decoder to use gapless playback (if possible)?

Correct. 

[grums]

Thanks, both - I noticed that NeroAAC encoder is specifically mentioned in the release notes (FS#12185) as being able to produce correct files to be played by r3.9.1 - I would be very grateful if a knowledgeable person would reveal the magic instructions for the 1.5.4.0 encoder version?

(I've tried: --help for the encoder, quickly browsing hydrogenauido and Nero sites).

PS: Why AAC when Vorbis playback works fine? Because my Zen will not play Vorbis; I suspect it might not be able to play gapless AAC, but then at least I only have to encode once for 2 players...

[saratoga]

Thanks, both - I noticed that NeroAAC encoder is specifically mentioned in the release notes (FS#12185) as being able to produce correct files to be played by r3.9.1 - I would be very grateful if a knowledgeable person would reveal the magic instructions for the 1.5.4.0 encoder version?

I doubt theres any difference between those versions, but you can check with Ahead if you're unsure.

[Lear]

Thanks, both - I noticed that NeroAAC encoder is specifically mentioned in the release notes (FS#12185) as being able to produce correct files to be played by r3.9.1 - I would be very grateful if a knowledgeable person would reveal the magic instructions for the 1.5.4.0 encoder version?

No magic needed. The encoder includes the gapless information automatically (I just tested on a small file). It is there in two formats, actually. At least the 1.5.4.0 version supports the iTunes tag format, which worked fine before 3.9.1. The fix was for the case when the iTunes tag was not present.

If you're still having problem with gapless playback, I'd start looking if something happens with the files after encoding but before playback by Rockbox.

[grums]

You're right: last night I found out that mp3tag wipes out 'unknown MP4 tags' in the version I used. I'll test untouched encoded files tonight.

Results of investigation: The MP3TAG program removes the (iTunes-) ITUNSMPB tag, which Nero AAC writes, and which presumably contains timing info concerning the end of the track vs. end of file.
Without this tag gapless playback is out of the question.
The website for MP3TAG claims that theses tags will be untouched, so maybe my settings are incorrect - I'll return when I have a conclusion.
Until then I'll use TAGSCAN - hopefully without side-effects...

Playback is much better now, BUT: I hear a small pop when switching tracks, it's not a delay between the tracks, and it's not there when I play FLAC or Vorbis - any ideas?

[Lear]

The MP3TAG program removes the (iTunes-) ITUNSMPB tag, which Nero AAC writes, and which presumably contains timing info concerning the end of the track vs. end of file.

Do you mean the program at http://www.mp3tag.de? That one doesn't remove the ITUNSMPB tag when I use it. And yes, that tag contains gapless information.

Without this tag gapless playback is out of the question.

Actually, not by itself. Nero writes gapless in another format too, that Rockbox also supports. A program could remove that other format too, though.

Playback is much better now, BUT: I hear a small pop when switching tracks, it's not a delay between the tracks, and it's not there when I play FLAC or Vorbis - any ideas?

Not really. But what do you mean by "switching"? Pressing next?

[grums]

Do you mean the program at http://www.mp3tag.de? That one doesn't remove the ITUNSMPB tag when I use it. And yes, that tag contains gapless information.

OK, thanks - but it does for me; I'll look into the settings.
BTW, I copy tags from the FLAC-files and paste them into the AAC-files.

Not really. But what do you mean by "switching"? Pressing next?

By switching I mean when player stops playing at the end of one track and starts playing at the beginning of the next - I'm not interfering.

[Llorean]

If it's just a small discontinuity, "gapless" for lossy files (like AAC) is almost never perfect. The samples at the end of one track won't match up perfectly with those at the beginning of the next, so there may be a noticeable difference. This may be what you're hearing.

[grums]

If it's just a small discontinuity, "gapless" for lossy files (like AAC) is almost never perfect. The samples at the end of one track won't match up perfectly with those at the beginning of the next, so there may be a noticeable difference. This may be what you're hearing.

Right - to sum up:

• It's very difficult to produce AAC files allowing a perfect gapless playback
• Rockbox (from r3.9.1) will do a perfect gapless playback of AAC files allowing such a playback (confirmed by others)
• Vorbis files will always allow a perfect gapless playback (because Vorbis is designed to facilitate this)
• The mp3tag program will destroy all existing tags when pasting (current discussion on their forum)

Thanks all