[vlc-devel] Re: OGG, AC3 encoder and maximum bitrate for video encoding

Håvar Illøkken Nielsen havar at illokken.net
Mon Dec 12 12:31:35 CET 2005

Måns Rullgård wrote:

>Derk-Jan Hartman <hartman at videolan.org> writes:
>>On 11-dec-2005, at 14:46, Håvar Nielsen wrote:
>>>The player does not seem to recognize comments in ogg streams.
>>I believe all comments in ogg files are added to the Information
>>dialog. The problem however is that OGG comments are not
>>standardised, and therefore an artist/title pair match cannot always
>>be made.
>In a fit of lunacy, the creators of the Ogg format and Vorbis codec
>decided to place the comments in Vorbis stream, and not at the Ogg
>container level.  Hence, talking about Ogg comments is meaningless.
>That said, the Vorbis comments are free-form, but there is a
>recommended set which should be supported.
>See http://xiph.org/vorbis/doc/v-comment.html

The act of placing comments at stream level was in my opinion an act of 
genious and far from lunacy. In a file with several audio-streams and 
subtitle streams, there would be a need for commenting something like:
comment[1]="TITLE=Movie sound 5.1 OGG"
comment[1]="TITLE=Director's comments"

And there are room for containerlevel commenting:
comment[0]="TITLE=The Matrix"

This kind of commenting is supported in other players, for instance 
Gabest Media Player Classic for Windows. And this is really what makes 
the OGG container unique and in my opinion the best container around. I 
think at least the LANGUAGE tag of the audio and subtitle streams should 
make it into the menus, the way they do with DVDs.

>>>And it doesn't handle 5.1 OGG sound very well.
>>I'm not sure if this is implemented at all in VLC. I am sure that
>>it's not much tested at the very least :D
>Not even oggenc/oggdec handle this very well.  It's not terribly
>difficult to do it though, assuming VLC already knows how to deal with
>5.1 audio in general.
ffmpeg, or at least the windows version of ffmpeg, ffdshow handles this fairly well. It can decode and reecode both OGG5.1 and AAC5.1 into an AC3 stream and send it over the SPDIF outlet. I haven't gotten around to installing Linux on my new AMD64 nf4 box yet, so I don't really know if the linux version of ffmpeg does handle it. VLC 0.8.4 and the daily build from Des 7. did play OGG5.1, but only the front channels as PCM.

Also, xbox media center, based on the linux mplayer does reencode OGG5.1 into AC3, the way I'm talking about. This player is also handling the OGG stream commenting in a sufficient way.


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