[vorbis-dev] New Directshow filters preview...

[illiminable]

Comments inline...

----- Original Message ----- 
From: "Ralph Giles" <giles at xiph.org>
To: <vorbis-dev at xiph.org>
Sent: Tuesday, March 23, 2004 2:22 PM
Subject: Re: [vorbis-dev] New Directshow filters preview...

<p>> On Tue, Mar 23, 2004 at 01:48:02PM +0800, illiminable wrote:
>
> > The streaming is a slightly different issue... most directshow filters
are
> > implemented as transform filters and allow directshow to supply the
source
> > filter... there are several limitations to doing this, and this
> > implementation imlpemnts the demuxer as a source filter for various
reasons.
> > This does however mean that i have to write the network support myself
> > rather than leveraging the existing URL source filter. This was a
conscious
> > decision as a beleive the benefits of havin the demux as a source
outweigh
> > the small amount of work i will need to include network code.
>
> Does DirectShow not have support for a separate demux plugin between the
> source and decoders? (I don't know anything about it) Seems like taking
> advantage of the graph would make your plugins more flexible in the
> future.
>

Yes it does... but as i mentioned there were significant problems i found
with this approach because it means you have the link between the source and
the demux as being a  pull model and then all the downstream filters being a
push model. In particular when it comes to seeking in ogg, this turned out
to be a lot more difficult to implement using the "Demux as transform
filter" approach. Also... the source filters have forced alignments of 512
bytes, which causes you to have to included all kind of offset corrections
all through the code to account for.

Once i implemnt network code into the source/demux it will be just as
flexible as any other source filter. In my opinion it actually makes it more
flexible by giving you better control over the file/source data.

> I bring it up because a real problem we have with the vorbis quicktime
> plugin (qtcomponents.sf.net) is that it embeds the Ogg mux directly.
> So while it can read and write Ogg Vorbis, you can't include Vorbis
> audio in a .mov file. So we have a perverse situation where you can
> export a quicktime movie using the now-free VP3 codec (which could be
> losslessly transcoded to OggTheora) but you *have* to use one of Apple's
> proprietary audio codecs.

The decoders are definately separate from the demuxer, so this shouldn't be
a problem.

>
> FWIW,
>  -r
> --- >8 ----
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<p>--- >8 ----
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