[vorbis-dev] Multi-stream vorbis...

[illiminable]

----- Original Message ----- 
From: "Ralph Giles" <giles at xiph.org>
To: <vorbis-dev at xiph.org>
Sent: Monday, May 31, 2004 12:22 AM
Subject: Re: [vorbis-dev] Multi-stream vorbis...

<p>> Yes. I mean, they'd need a mixer and a way to maintain sync which are
> significant extra features. Vorbis is a lossy distribution format
> so generally you care more about bitrate than being about to turn
> portions of the audio on an off. We've always viewed that as a
> specialized application that needn't be universally supported.
>

OK... fair enough... i guess i take it for granted all that stuff is
automagically done for me :)

> (This is in contrast to *alternate* audio tracks, which we do support in
> theora.)
>

OK... that's good.

> No good one. Vorbisfile didn't support muxed streams at all, and one one
> fixed it by the the 1.0 release. Unfortunately, Monty broke the spec to
> match the lib instead. Playing (at least) the first occurring vorbis
> stream is what players *should* do.
>
> The convention is that the first occurring header packet determines the
> 'primary' media type of the stream. This lets you do file magic
> identification of vorbis vs speex vs theora, etc. Of course theora files
> can also contain vorbis, but you shouldn't expect players to play the
> video if it doesn't occur in the first page.
>

Which gets back to my other point of the file extension again (in case you
haven't noticed, i really think something needs to be done about this !). I
think it will be a mistake to keep a single extension after theora becomes
beta. Windows relies very heavily on file extensions to determine what
applications can play something and what kind of content it contains.

The way i see it, if you have a single .ogg extension and ogg is supposed to
be a generic format, you should be able to handle any combination of known
codecs. And that aside there are other end-user issues.

There's two kinds of platforms wrt to file extensions...
1) Those that don't care
2) Those that do.

Those that don't care don't matter what you use and those that do will have
significant end-user irritation with a single extension. I don't see what
advantage the single extension offers. It's no accident that just about
every other major media format have different extensions, wmv and wma, mpg
and mp3, rm and ra etc. or where they aren't paired formats, you can always
distinguish audio from video.

My personal opinion is that there should be 3 (or more) extensions to
distinguish between vanilla audio, vanilla video(theora+vorbis) and anything
goes ogg. Because no player can actaully handle ogg as a generic format...
only a collection of subsets of it, to me it makes no sense to lump all
these together under one extension. Why have a generic format with a single
extension when the players only support certain set combinations.

What you lose by having a single extension is....
a) The ability to determine a file type at a glance... i've already started
double extensioning all my test files, because it annoyed me i had to keep
looking at the headers in a hex editor to see what type of file i was
testing. People like to know in advance if they are about to open a video or
an audio file.

b) In a networked situation, people may be willing to stream audio, but not
have the bandwidth for video... the url alone won't let them make that
decision without just trying and see what happens

c) You lose the ability to have seperate players be the default player for
different types of files... for example i have iTunes attached to all audio
files, and WMP attahed to all video files. If there is a single extension
for ogg, i will have the problem that i will attach .ogg to iTunes... and
then have to manually open theora files with wmp. It also means iTunes or
other audio only player will also accidentally attempt to bring ogg theora
files, or ogg files with other things in them into it's library, and theres
no easy way for the end user to realise whether it didn't work because the
file is damaged or because it is just the wrong type for the player.

d) The ability to have distinct icons for different types. ie iTunes shows a
different icon for mp3 and aac by overlaying mp3 or aac over the itunes
icon.

e) Abililty for file type filters in applications to show directory subsets
of video or audio files.

And as i see it you don't gain anything by having a single type except some
kind of branding.

Cheers,

Zen.

<p>--- >8 ----
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