[Vorbis-dev] Enhanced Podcasts with Ogg Vorbis (Chapter Marks)

Georg Holzmann grh at mur.at
Fri Jan 6 02:25:06 PST 2012

Hello list!

Since it is more and more common these days to create enhanced podcasts 
(= audio files with additional chapter markers [1]), I am searching for 
an alternative to the currently used MP4 format.
ID3 also puplished an official standard for chapters [2], but nobody 
seems to use and support it.

Now I am trying to get something similar with vorbis audio (and maybe an 
additional container).
So far I am aware of the following possibilities:

1) Matroska Audio with Chapter Marks

Using the matroska container, it is possible to generate a matroska 
audio file (mka) with included chapters (see [3] for the exact command).

- many media players and some hardware players support matroska, see [4]
- with e.g. VLC (or foobar) you see chapters and are able to seek in the 
audio file - very nice!
- android 4 should support matroska natively [5] (but I don't think that 
it's possible to see the chapters ?)

- many hardward players, which support ogg vorbis, are not able to play 
mka files
- I found no app on android so far which can play mka files

2) OGM Container with Chapter Marks

Using the same chapter.txt file, I created an OGM container with ogg 
vorbis audio:
$ ogmmerge -o output.ogm audio_track.ogg chapters.txt

This seems to work, at least ogmmerge says so on the command line:
   +-> Using Vorbis audio output module for stream 1.
   Using chapter information reader for chapters.txt. working... -

- I could not find any player which is able to show the chapters
- many players don't support ogm (winamp, foobar, ... - maybe with plugins)
- hardward players don't support ogm, also android has no ogm support AFAIK

So maybe I did something wrong here? Or does anyone know a player where 
OGM chapters work?

3) Concatenating ogg files

This method was described here: [6]. Each chapter must be one ogg vorbis 
file and then they are concatenated in one big file:
$ cat chapter1.ogg chapter2.ogg chapter3.ogg > all_chapters.ogg

- this method is fully ogg vorbis compatible, cheap hardware players 
also play these files
- foobar lists the individual files and it's able to seek

- I found no other player so far which is able to display these "chapters"
- IMHO it's a hack and no real solution

At the moment I think that matroska is the cleanest solution, however, 
maybe there are still some other possibilities?
For instance:

- Using Vorbis Comments:

Wouldn't it be easier to just use vorbis comments for chapter information ?
E.g. add to the vorbis comments:
   CHAPTER01NAME=Chapter 01
   CHAPTER02NAME=Chapter 02

If some agree on this or a some similar recommendation, is it realistic 
that players will support it?
The big advantage would be, that all cheap hardware ogg vorbis players 
would still be able to play at least the audio ...

- WebM Container:

Is it possible to use WebM instead of Matroska as a container?
AFAIK there is unfortunately no chapter support in WebM (although they 
build on Matroska) ...

- Using OGG:

According to wikipedia, OGG is able to add chapters (see the comparison 
table in [7]).
Am I missing something here? Because this would be really nice!

OK, sorry for the long mail :)
Any hints on how to create enhanced podcasts with the widest range of 
support (software players, hardware players, android, ...) would be 
highly appreciated.
I really like the way it is possible in MP4 and something similar as an 
additional (and open source) format would be very useful!

Thanks for any hints!

PS: please let me know if vorbis-dev is not the correct mailing list for 
this question!

[1]: http://en.wikipedia.org/wiki/Enhanced_podcast
[2]: http://www.id3.org/id3v2-chapters-1.0
[3]: http://savvyadmin.com/adding-chapters-to-videos-using-mkv-containers/
[4]: http://en.wikipedia.org/wiki/Matroska#Software_support
[5]: http://developer.android.com/guide/appendix/media-formats.html
[6]: http://lists.xiph.org/pipermail/vorbis/2005-September/025969.html

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