[Flac-dev] Re: multiple core support

[Harry Sack]

2007/9/8, Brian Willoughby <brianw at sounds.wa.com>:
>
> Ralph,
>
> The problem is that there is no clear advantage, at least in terms of
> multiple cores, to the approach you're asking about.  In order to
> allow each stage of the codec to overlap, you need smart buffering
> between each stage.  That adds code and complexity which isn't there
> currently.  So you end up making the system do more work in the hopes
> that there will be some overlap.  Basically, later stages get blocked
> waiting for their input buffer to fill, which means that you're not
> really getting very much overlap at all, but plenty of multi-
> threading overhead.  At least that's the predicted result - I admit
> that nobody has tried this, to my knowledge.



this is because of the limitations/design problem of FLAC API in particular.
When the developers had made a smart decision and based everything on file
based I/O you would get a HUGE performance boos when using multiple threads
divided between multiple cores, because they only thing to do was to split
the file output in different threads.
But it's not clear to me why everything was based on streams...

Harry

Brian Willoughby
> Sound Consulting
>
>
> On Sep 7, 2007, at 18:25, Ralph Giles wrote:
>
> On Fri, Sep 07, 2007 at 04:59:50PM -0700, Josh Coalson wrote:
>
> > it actually is complicated.  the libFLAC api is not suited to a
> > multithreaded design because the i/o is stream-based, not file-
> > based.  flac(.exe) is the file-based wrapper around libFLAC that
> > allows it to work on files.  the way libFLAC buffers data is also
> > impossible to parallelize without significantly changing the api.
>
> It seems like buffering (especially compressed) blocks and writing them
> to the stream in sequence wouldn't be a problem. Is there something in
> the way the blocking decisions are made that makes it hard to divide the
> input audio this way?
>
>   -r
>
> _______________________________________________
> Flac-dev mailing list
> Flac-dev at xiph.org
> http://lists.xiph.org/mailman/listinfo/flac-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.xiph.org/pipermail/flac-dev/attachments/20070908/72e8c009/attachment.htm