[Ffmpeg-devel] swscaler integration

Rich Felker dalias
Thu Mar 16 17:34:19 CET 2006

On Thu, Mar 16, 2006 at 12:58:14PM +0100, Erik Slagter wrote:
> On Thu, 2006-03-16 at 00:06 -0500, Dave Dodge wrote:
> > > So, decoupling crop/scale/pad may not be the best solution after
> > > all. But maybe that would have to be *another* filter?
> > 
> > The real difficulty is if you have to _seek_ in the data.  The pipes
> > destroy that capability unless you implement buffering or require some
> > other way of doing I/O.
> Not to mention:
>  - multiple streams (either audio/video) in one container
>  - timestamps
>  - other metadata carried in the input container or stream (if decoding)
> And indeed, running all of this over standard 4k pipes is ehm...
> non-optimal. Using a socketpair of 64 kb might help somewhat, but that
> would be as complex as using shared memory which of course beats the
> hell out of every other mechanism. Either way, you won't have the nice
> pipeline syntax.
> I never understood why no unix version has a ioctl to set the pipe
> buffer size.

I guess then the kernel implementation would be a lot more complex
(not just using a single page) and there would have to be a mechanism
to prevent unbounded memory usage by pipe buffers. As it stands, a
sane open file limit provides a decent (altho somewhat large) pipe
buffer limit. But maybe this is already handled some other way


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