Along with iTunes 4.9, which supports "podcasting" (I am beginning to hate the word), Apple released Podcast Chapter Tool (beta, OS X, command-line) to create "Enhanced Podcasts" (sigh…). Check the fragment of the readme in bold letters:



iTunes 4.9, thus, detects when a m4a file has chapters in it and will add a new button on the fly at the left of the display (see image below) to choose chapter inside a track.



QuickTime 7.0.1, surprisingly, is not be able to open m4a files with chapters. iPods just received a firmware update, which, I think, gives them support for chapters.

Anybody knows how "standard" to the mp4 container is this thingy? As in… do you think this will be supported by other players/encoders without resorting to dirty hacks? Does it relate somehow to how Nero Recode adds chapter support in mp4?

what does this have to do with chapters (as known from books, dvds and mp4 video files)?

i am absolutely sure that this is not part of the mpeg-4 standard

any sample files available?

As in the sense that you can fastforward to specific points in time through a drop down list (not the most comfortable interface, granted). Exactly the same meaning of chapters when applied to video, but for audio. Hence, you can have one whole album as a lone m4a audio file, but you are still able to choose which chapter (i.e. track) to play.

You've got a sample file if you download the Chapter Tool linked in the first message. It is a dmg disk image, so I do not know if you can access its contents with anything besides Mac OS X. If you tell me how, I can send it to you.

Why are you so fast to mention that it is not part of the mpeg-4 standard? Are chapters in mp4 video files part of the standard? The "chaptered" m4a could be exactly the same as one of those chaptered video files, minus the video. MP4 is just a container after all.

ok ic, i just wondered about these web links and pics connected to each chapter...


there is no official chapterstandard for .mp4

nero developed an own one and now apple seems to have done it too
it again prooves that everything not defined by an official independant specifying body leads to a mess

Or maybe it proves the MPEG is hopelessly slow answering to demands from users and industry, eh?

How long have we been waiting for MPEG4 Lossless already? Apple themselves gave up waiting and released their only lossless format.

Which pretty much means ALS will be stillborn, as Apple is pushing forward adoption of the MPEG4 audio standards nearly by itself, and now they have their own format to push forward instead.

indeed,
i would say both statements dont contradict each other

The chapter mark data in the M4A files is seemingly stuck in the AAC stream itself. Perhaps between frames or something.

You can get a file with several embedded tags by using iTunes 4.9 to subscribe to the "iTunes New Music Tuesday" podcast, and downloading that podcast. The file is an M4A file and using a hex editor you can see the chapter mark data all along the file, just before each piece of music there. Each entry has the artist name, the song name, a JPEG cover art, and some other stuff in there.

Foobar 0.83 seems to have no problem playing the file. Plays right over these bits, no clicking or anything.

Do you mean all along the track or in some sort of header? It is weird that iTunes only displays available chapters once you hit play, while it does display album artwork just upon select. If there is not some sort of table of contents, it would be a crap, IMHO, because that would mean having to load the whole file into memory before being able to display chapters. Imagine doing that with full albums m4a… Did anyone try to play a podcast stream that is know to have chapters. Were they selectable without a previous full download?

Well, I am a complete ignorant in in this techy things, so what do I know.

Anyhow it still seems sounds like crap, to me, because if it is stuck into the aac stream and not in some sort of mp4 header, I guess its use cannot extend to mp4 with audio+video, video-only or multiple audio tracks.

IMHO, since both m4a and mp4 are exactly the same, both should be able to specify chapters the same way.

If they are embedding the metadata into the data itself, what's the container there for? It's weird how Apple being behind Quicktime does not use the existing framework to add at all.

There may be some kind of index to the data in the header, but the data appears to be all along the track itself. I assume this is how it displays the list of tracks with album art: Some kind of index in the header pointing to the data, and when it encounters the data while playing the track it switches the display at that time.

when i look at the udta.meta atom (udta is the place where private stuff like chapters and what not belongs to) its fairly big, maybe thats where the info is stored?

The chapters also get copied to the iTunesDB file on iPod's, although I don't think the form is the same. I've documented some of the chapter stuff in the iTunesDB file on the iPodLinux wiki: http://ipodlinux.org/ITunesDB

In any case, the chapters, as far as the iPod cares, are in the iTunesDB file. It doesn't appear to use the stuff in the M4A file directly.

A closer look at Apple's ChapterTool:

Quick First Report on Chapter Tool Used on a Mac

Is there anything that provides this kind of functionality on a non-Mac platform?