[gmpi] Re: Topic 7: Audio packaging
- From: Tim Hockin <thockin@xxxxxxxxxx>
- To: gmpi@xxxxxxxxxxxxx
- Date: Wed, 21 May 2003 11:29:14 -0700 (PDT)
> (8: Are data blocks passed along down the stream and reused where
> possible, or effectively owned by a single i/o connection pair? Is it
> legal to expect a plug to use the same buffer for input and output and
> pass it on?)
Buffers should be re-usable (allocated by the host) except in a few cases
(see below).
Plugins should be able to identify whether they can use the same input and
output buffers, or whether they need different buffers. Default to assuming
that all buffers are distinct, and let plugins specify "I'm in-place safe!"
or vice versa. I don't know that the default matters. Saying "I'm in-place
safe!" is a good PR point for plug makers, but being forced to say "I'm
in-place broken" is also pretty strong.
It was mentioned that plugins may want to allocate their own buffers (device
memory or whatnot). Should this be allowed, or should we make this the
responsibility of the proxy to copy the data in/out of device memory?
Also, wrt buffers - something we talked about in XAP: optimizing plugs
during silence. Buffers originate at instruments. If the instrument
doesn't produce any data, the buffer is effectively silent. Some plugins
might be able to skip some work if their input is silence. So what we
talked about was this (totally optional for host and plugins):
1) Flag all buffers as SILENT.
2) Whenever a plug writes to a buffer, remove the SILENT flag.
3) Any downstream plug can see the SILENT flag and do whatever it wants with
it.
Hosts can just never set the SILENT flag, and it will never bother anyone.
But if they want, they can set the SILENT flag and avoid some work (no need
to zero the buffer if we know it is silent, maybe?). Plugins that respect
the SILENT flag might avoid some work, and plugins that don't would do their
thing. The only thing required is that plugins need to identify whether
they can accept SILENT buffers.
Tim
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