Ogg files with two streams fail.

[hiptobecubic]

Some of my ogg files won't play in rockbox, despite working everywhere else i've tried. I created them with ffmpeg2theora. VLC, mplayer, and mpd all play the file fine, although VLC fails to find the Vorbis comment header, "TagLib: Vorbis::File::read() - Could not find the Vorbis comment header."

According to /bin/file, the files that won't play are of type
"Wontplay_inrockbox.oga: Ogg data, Skeleton v4.0", whereas the working ogg looks like
"Willplay_inrockbox.ogg: Ogg data, Vorbis audio, stereo, 44100 Hz, ~96000 bps".

/usr/bin/ogginfo says that the file that won't play has two streams, a skeleton stream and a vorbis stream, whereas the working file only has a vorbis stream. I'm sure that's somehow the issue, but can anyone say what's really going on here? Is it a case of rockbox and VLC not working hard enough to support the various ways that vorbis can be put into an ogg container, or this way just illegal?

Code: [Select]

john@eleanor:/dev/shm$ ogginfo Wontplay_inrockbox.oga 
Processing file "Wontplay_inrockbox.oga"...

New logical stream (#1, serial: 0e483fe6): type skeleton
New logical stream (#2, serial: 0e483fe4): type vorbis
Vorbis headers parsed for stream 2, information follows...
Version: 0
Vendor: Xiph.Org libVorbis I 20101101 (Schaufenugget)
Channels: 2
Rate: 44100

Nominal bitrate: 80.000000 kb/s
Upper bitrate not set
Lower bitrate not set
User comments section follows...
	ARTIST=Artisan
	TITLE=Speed
	ALBUM ARTIST=Artisan
	ALBUM=Rocking at the End of Time
	TRACKNUMBER=6
	GENRE=Folk Harmony
Logical stream 1 ended
Vorbis stream 2:
	Total data length: 1033092 bytes
	Playback length: 1m:56.089s
	Average bitrate: 71.192725 kb/s
Logical stream 2 ended

john@eleanor:/dev/shm$ ogginfo Willplay_inrockbox.ogg
Processing file "Willplay_inrockbox.ogg"...

New logical stream (#1, serial: 30517eee): type vorbis
Vorbis headers parsed for stream 1, information follows...
Version: 0
Vendor: AO; aoTuV b4b [20051117] (based on Xiph.Org's libVorbis)
Channels: 2
Rate: 44100

Nominal bitrate: 96.000000 kb/s
Upper bitrate not set
Lower bitrate not set
User comments section follows...
	ARTIST=Artisan
	TITLE=Speed
	ALBUM ARTIST=Artisan
	ALBUM=Rocking at the End of Time
	TRACKNUMBER=6
	GENRE=Folk Harmony
Vorbis stream 1:
	Total data length: 1359654 bytes
	Playback length: 1m:56.075s
	Average bitrate: 93.708572 kb/s
Logical stream 1 ended

[saratoga]

Theres a description of Ogg Skeleton here:

http://wiki.xiph.org/Ogg_Skeleton_4

I've actually never heard of it before, but I think its pretty safe to say that we don't support it.

[hiptobecubic]

Ok I see. Well reading the Xiph page:

Ogg Skeleton is a logical bitstream within an Ogg stream that contains information about the other encapsulated logical bitstreams. For each logical bitstream it provides information such as its media type, and explains the way the granulepos field in Ogg pages is mapped to time.


So the skeleton stream simply identifies the Vorbis stream that rockbox was expecting to find in the first place. I don't have any experience hacking on media libraries, but since this isn't a new codec or anything, is it a reasonable feature request? I can see problems arising if perhaps there are multiple media streams in the file, but a sensible default like "ignore all but the first vorbis stream" is better than the current behavior of dying without any errors. Thoughts?

[Llorean]

We never like "dies without any errors" but typically speaking something like this (especially since you're the first person in years to have even experienced this problem) gets fixed if someone with a specific interest in it actually goes and submits a patch that includes a fix.

[hiptobecubic]

Is this the direction that ogg is moving towards in the future? Their description of the ambiguity problem that it solves would suggest so. If so, would this end up on the list of "things which are necessary" instead of "patches welcome"? I'd like to fix this myself, but I'm starting from absolute zero: No knowledge of how rockbox works, no knowledge of how codecs work, etc.

[saratoga]

Is this the direction that ogg is moving towards in the future?

You'd have to ask Xiph.

[hiptobecubic]

So I talked to some people in #xiph and learned the following.

"*.ogg" implies a single stream ogg container with a vorbis stream in it.
"*.oga" implies that a skeleton stream is present which indicates any other streams that might be present, of which more than one may be vorbis, speex, theora, etc.

The latest spec will demand that skeletons be present in ogg files. "Vorbis" files are grandfathered in with their degenerate ogg container format, freely admitted by them to be an error caused by rushing the standard out the door originally.

The "right" thing to do is to add support for Ogg containers with a skeleton as that is what the spec calls for, while keeping support for the original Vorbis-only format that rockbox currently has.

The full conversation is here: http://pastebin.com/D0LjMfvS,  and is also attached.

[torne]

Thanks for the information. However, we don't actually have a list of "things which are necessary" - everything is "patches welcome"

[hiptobecubic]

Wish I could be a little more helpful here. I'd like to learn more about how this kind of thing works. Where does one begin? My knowledge of C is pretty decent, but as I mentioned before, I have never dug into the Rockbox codebase or done any parsing of codecs or anything before.  Would be nice to add my name to the list of contributors though