[Flac-dev] Re: multiple core support

[Josh Coalson]

--- Harry Sack <tranzedude at gmail.com> wrote:
> 2007/9/8, Josh Coalson <xflac at yahoo.com>:
> >
> > 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.
> 
> why was this approach used?

because the tradeoffs I described required for arbitrarily parallel
encoding significantly complicate the api and implementation.
libFLAC was not design for multicode file encoding on PCs, it is a
reference design that is also being used in embedded devices running
<100MHz, low memory, all kinds of different OSes, etc.

> The API design seems to me not very smart
> because it's not flexible and you're stuck in the future (like now
> for multiple core support)
>
> I don't see any reason why you wouldn't make it all based on files
> and not on streams :s It's just a major disavantage in my opinion

an api cannot be all things to everyone.  you keep making this
assertion but if you actually tried to implement it (and I hope
you will) the problems we are all bringing up will quickly become
obvious.

your own lame-mt example is not an incremental improvement but a
significant rewrite of lame (and also does not have nearly the
performance advantage of process-level parallelism, see
http://www.hydrogenaudio.org/forums/index.php?showtopic=50862)

> > it would take a specialty file-based encoder using an independent
> > frame encoder to do and even that is not trivial.
> 
> so we can assume that those API changes will never come and the flac
> encoder will never have multiple core support?

you can assume libFLAC will probably not have it.  if you can modify
libFLAC to make a multithreaded encoder like flac-mt that would be
neat and probably useful to some people.  until that time there is
not much point repeating the same assertions which are just going to
aggravate people.

Josh



       
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