Rockbox Technical Forums

Support and General Use => Audio Playback, Database and Playlists => Topic started by: michael.conner on December 01, 2006, 06:58:44 PM

Title: "enhanced" aac podcasts
Post by: michael.conner on December 01, 2006, 06:58:44 PM
Is there any way to get these to work under Rockbox (other than transcoding to another format)? foobar2k treats them as normal aac files, but Rockbox goes to the WPS and then immediately returns to the file browser window.  
Title: Re: "enhanced" aac podcasts
Post by: Llorean on December 01, 2006, 07:46:05 PM
What exactly do you mean by enhanced? The word enhanced in quotation marks doesn't mean much on its own.
Title: Re: "enhanced" aac podcasts
Post by: michael.conner on December 01, 2006, 08:02:04 PM
What exactly do you mean by enhanced? The word enhanced in quotation marks doesn't mean much on its own.

Good point.  Enhanced podcasts are ones that have embedded pictures, chapter markers (so you can skip forward within the track), etc., within the M4A file.
Title: Re: "enhanced" aac podcasts
Post by: bk on December 01, 2006, 08:25:42 PM
See this thread: http://forums.rockbox.org/index.php?topic=7288.0

The 'enhanced' podcasts I've tried show similar metadata errors with mp4dump.
Title: Re: "enhanced" aac podcasts
Post by: bk on December 03, 2006, 12:31:59 PM
Thanks to the recent commit ("3 Dec 13:51: Magnus Holmgren: Remove some unneeded code that caused problems for enhanced AAC files.") my enhanced podcasts now load and display metadata normally. Unfortunately they bomb out with a codec failure before the audio starts playing.
Title: Re: "enhanced" aac podcasts
Post by: Lear on December 04, 2006, 04:16:37 AM
You sure you tested a build with the fix? Before that fix, it would load and display metadata properly, but "bomb out" with a codec failure...
Title: Re: "enhanced" aac podcasts
Post by: bk on December 04, 2006, 08:13:27 AM
No, before that fix it wouldn't load at all. It would be skipped completely and the next track would be played.
Title: Re: "enhanced" aac podcasts
Post by: Lear on December 04, 2006, 08:22:53 AM
Hm... Do you have a link to a podcast that shows the problem? The change I did was for the codec only, so it must be that the fix only solved part of the problem. It worked fine for the podcast I tested with though.
Title: Re: "enhanced" aac podcasts
Post by: bk on December 04, 2006, 09:04:02 AM
Sure. http://75minutes.dreamhosters.com/audio/75minutes_69.m4a

Thanks for working on this.
Title: Re: "enhanced" aac podcasts
Post by: Lear on December 04, 2006, 10:21:20 AM
Ah, that podcast fails for an entirely different reason - it's too long. :)

That's a known limitation in Rockbox. A table that is used during decode - and to calculate seek positions - is too large. I think it is possible to reduce the size of that table, but I haven't looked closer at it yet.
Title: Re: "enhanced" aac podcasts
Post by: michael.conner on December 04, 2006, 01:53:33 PM
Here's another one:

http://media.scifi.com/battlestar/downloads/podcast/m4a/308/bsg_episode_308_commentary_enhanced.m4a
Title: Re: "enhanced" aac podcasts
Post by: Lear on December 05, 2006, 04:03:58 AM
Here's another one:

http://media.scifi.com/battlestar/downloads/podcast/m4a/308/bsg_episode_308_commentary_enhanced.m4a

"The page you requested was not found."

However, if it is long (a bit over one hour), it is likely to fail for the same reason.
Title: Re: "enhanced" aac podcasts
Post by: michael.conner on December 05, 2006, 10:05:59 AM
That's really weird about the link to that podcast I posted not working.  I clicked on it a few times just now, and 1 out of every 3 or 4 times, it would work -- the other times I'd get the "page not found error."

If it'd be useful, I can post what mp4dump says about the file.   The podcast is only 45 minutes or so.
Title: Re: "enhanced" aac podcasts
Post by: Lear on December 06, 2006, 11:17:03 AM
Indeed, after several tries, I finally got it. This one fails because of an "unexpected" file structure. The metadata parser seems to handle it well, but the one in the codec isn't quite as flexible. Shouldn't be that hard to fix, I think, but I need to examine the file in more detail first.
Title: Re: "enhanced" aac podcasts
Post by: michael.conner on December 06, 2006, 04:59:47 PM
The latest CVS fixed it.   Thanks!
Title: Re: "enhanced" aac podcasts
Post by: NicolasP on December 06, 2006, 08:01:14 PM
I still have a podcast that doesn't work. It's pretty heavily enhanced with pictures and chapters. Even "mp4creator -optimise" (from mpeg4ip) doesn't make it work, so I have to extract the audio track, create a new MP4 file from it, tag it and then optimise it in order to be able to listen to these files on my H320. I've made a script for it but it would be really nice if i could just copy the original files over to my DAP :)
You can download the latest episode here (http://get.podemus.com/gumprod/medias.joachimgarraud.com/sound/zemixx/Zemixx96.m4b).
It's M4B, but just rename it to M4A ;)
Title: Re: "enhanced" aac podcasts
Post by: Lear on December 07, 2006, 01:28:31 AM
You can download the latest episode here (http://get.podemus.com/gumprod/medias.joachimgarraud.com/sound/zemixx/Zemixx96.m4b).

"Server not found"...
Title: Re: "enhanced" aac podcasts
Post by: NicolasP on December 07, 2006, 01:52:09 AM
You can download the latest episode here (http://get.podemus.com/gumprod/medias.joachimgarraud.com/sound/zemixx/Zemixx96.m4b).
"Server not found"...
That's strange, it works fine for me...
I've uploaded it to one of my web spaces : link (http://nicolas.pennequin.free.fr/Zemixx96.m4b).
Thanks for having a look :)
Title: Re: "enhanced" aac podcasts
Post by: Lear on December 07, 2006, 04:36:33 AM
I tried again (from another computer) and then it worked... Anyway, that file should play now.
Title: Re: "enhanced" aac podcasts
Post by: NicolasP on December 07, 2006, 06:55:42 AM
Sweet ! Thanks a lot :)
Most of the episodes work fine now, but i still have some problems.
There are a few which load fine but produce a horrible noise. You can get one of these here (http://nicolas.pennequin.free.fr/Zemixx84.m4b).
Also there is one that doesn't load at all : link (http://nicolas.pennequin.free.fr/Zemixx94.m4b).

And there's one last thing I'd like to mention, it's that your commit said "accept M4B files". Maybe it's not what you meant but I thought I would actually be able to play files with an M4B extension... Maybe as most of them are now playable you could add support for that extension in the browser ?
Title: Re: "enhanced" aac podcasts
Post by: Lear on December 07, 2006, 08:11:29 AM
Sweet ! Thanks a lot :)
Most of the episodes work fine now, but i still have some problems.
There are a few which load fine but produce a horrible noise. You can get one of these here (http://nicolas.pennequin.free.fr/Zemixx84.m4b).
Also there is one that doesn't load at all : link (http://nicolas.pennequin.free.fr/Zemixx94.m4b).

The hiss is a side effect of the decoder running out of memory... :) The other one is a file parsing problem; don't know what just yet.

Quote
And there's one last thing I'd like to mention, it's that your commit said "accept M4B files". Maybe it's not what you meant but I thought I would actually be able to play files with an M4B extension... Maybe as most of them are now playable you could add support for that extension in the browser ?

No, that M4B thing I referred to is something that can be found inside the file. Adding support for the extension could be a good idea.
Title: Re: "enhanced" aac podcasts
Post by: NicolasP on December 07, 2006, 08:24:24 AM
How come the decoder runs out of memory on some files and not others ? This is even more surprising as these episodes used to play fine after being modified by my script...
Title: Re: "enhanced" aac podcasts
Post by: Lear on December 07, 2006, 08:45:47 AM
How come the decoder runs out of memory on some files and not others ? This is even more surprising as these episodes used to play fine after being modified by my script...

The size of various tables used for seeking (and playback). Your script can change the file layout, and also make some tables more compact. This can reduce the size of the tables, making it possible to load the file.

Btw, the file that didn't load fails because the file isn't streaming friendly (which Rockbox currently requires); the metadata comes after the audio data.
Title: Re: "enhanced" aac podcasts
Post by: NicolasP on December 07, 2006, 09:41:39 AM
Thanks for the explanation :) Is there any chance these files will work in the future, or should I just run them through my script ?
Also about the one that wasn't streaming friendly, foobar corrected it perfectly so now it works fine.

Now there is something else I noticed, about replay gain : the value is taken into account (there is a distinct volume jump when I enable/disable replay gain), but in the ID3 info screen, the value shown under "track gain" is the track title ;D I haven't tried album gain...

Finally, would you have any idea on how to read the bookmark time tags stored in these M4B files ? It would be a very nice feature to add and maybe I'd try doing so.
Title: Re: "enhanced" aac podcasts
Post by: Yotto on December 07, 2006, 10:04:30 AM
Do the producers of the show not produce a non-enhanced version of their show?  As a podcaster (though as one who does not produce an enhanced version) I can't imagine producing ONLY an enhanced podcast, and not also provide a good old fashioned mp3 file as well.
Title: Re: "enhanced" aac podcasts
Post by: NicolasP on December 07, 2006, 10:18:24 AM
No, sadly they don't. They seem to think everyone listening to their podcasts has an iPod and iTunes >:(
It goes as far as making it almost mandatory to use iTunes to even subscribe to the podcasts...
Title: Re: "enhanced" aac podcasts
Post by: Lear on December 07, 2006, 11:19:06 AM
Thanks for the explanation :) Is there any chance these files will work in the future, or should I just run them through my script ?

Possibly. I have some ideas on how it could be fixed, at the expense of some seek accuracy on long files (a 1 hour file can have about 120.000 seek points, which is a little excessive, IMHO). Not sure if it will work though, and getting it right could be a little tricky... :)

Quote
Now there is something else I noticed, about replay gain : the value is taken into account (there is a distinct volume jump when I enable/disable replay gain), but in the ID3 info screen, the value shown under "track gain" is the track title ;D I haven't tried album gain...

Interesting bug. I did know that piece of code hadn't been tested, but I thought it should work. It almost did... Fix committed.

Quote
Finally, would you have any idea on how to read the bookmark time tags stored in these M4B files ? It would be a very nice feature to add and maybe I'd try doing so.

Nope, I don't know anything about those parts. I haven't tried to find out what kind of data it is, or how it can be used.
Title: Re: "enhanced" aac podcasts
Post by: Yotto on December 07, 2006, 12:38:08 PM
No, sadly they don't. They seem to think everyone listening to their podcasts has an iPod and iTunes >:(
It goes as far as making it almost mandatory to use iTunes to even subscribe to the podcasts...

Then I would email them, asking for an alternative, and if they would not provide one, I'd seriously consider unsubscribing.

There are tens of thousands of podcasts out there.  I bet there are dozens that do what this show does, and don't lock you into iTunes.
Title: Re: "enhanced" aac podcasts
Post by: NicolasP on December 08, 2006, 03:06:12 PM
Lear, thanks for your last two commits, now it's much easier to listen to podcasts :)

Yotto, I've started a discussion on the forum related to this podcast about providing an alternative in the form of an MP3 version, but I'm not very optimistic about the chances of getting it. The thing is this podcast is simply the most important when it comes to french electronic music so I don't really want to consider the option of unsubscribing ;)
Thankfully, the compatibility is now almost perfect, so it's not really a problem anymore, but I'll still try to push to get an MP3 version :)