[LV2] Buf size extension

[David Robillard]

Hi all,

I have committed a new extension to svn, which describes a feature that
allows the host to describe block length and buffer size information to
the plugin, as well as several features which allow the plugin to
express restrictions.

The restriction features are currently limited to what I know is
actually useful.  I feel this is better than trying to over-define the
thing, since others can easily be added in the future.  KISS and all
that.

Definition attached, also available in the SVN repository at
lv2/lv2plug.in/ns/ext/buf-size

Cheers,

-dr
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@prefix bufsz: <http://lv2plug.in/ns/ext/buf-size#> .
@prefix dcs:   <http://ontologi.es/doap-changeset#> .
@prefix doap:  <http://usefulinc.com/ns/doap#> .
@prefix foaf:  <http://xmlns.com/foaf/0.1/> .
@prefix lv2:   <http://lv2plug.in/ns/lv2core#> .
@prefix owl:   <http://www.w3.org/2002/07/owl#> .
@prefix rdf:   <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs:  <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xsd:   <http://www.w3.org/2001/XMLSchema#> .

<http://lv2plug.in/ns/ext/buf-size>
	a lv2:Specification ,
		lv2:Feature ;
	rdfs:seeAlso <buf-size.h> ,
		<../../meta/meta.ttl> ;
	doap:name "LV2 Buf Size Extension" ;
	doap:shortdesc "Access to, and restrictions on, buffer sizes." ;
	doap:created "2012-05-25" ;
	doap:developer <http://drobilla.net/drobilla#me> ;
	doap:release [
		doap:revision "1.0" ;
		doap:created "2012-04-17" ;
		doap:file-release <http://lv2plug.in/spec/lv2-1.0.0.tar.bz2> ;
		dcs:blame <http://drobilla.net/drobilla#me> ;
		dcs:changeset [
			dcs:item [
				rdfs:label "Initial release."
			]
		]
	] ;
	lv2:documentation """
<p>This extension defines a facility for plugins to get information about the
block length (the sample_count parameter of LV2_Descriptor::run) and
port buffer sizes, as well as several features which can be used to restrict
the block length.</p>

<p>Access to the relevant information is provided by the bufsz:access feature,
which may be used alone.  To express restrictions on the block length,
additional data-only features are defined: bufsz:boundedBlockLength,
bufsz:powerOf2BlockLength, and bufsz:fixedBlockLength.  There is currently no
facility for requiring specific values for the block length, this may be added
in the future if need arises.</p>
""" .

bufsz:access
	a lv2:Feature ;
	lv2:documentation """
<p>The feature that provides access to buffer size information.  This feature
is the only one in this extension which carries data: to implement it the host
passes a feature with URI LV2_BUF_SIZE__access and an LV2_Buf_Size_Feature
for data, which provides functions the plugin can call to investigate the
buffer size.</p>
""" .

bufsz:boundedBlockLength
	a lv2:Feature ;
	lv2:documentation """
<p>A feature that indicates the host will provide a minimum and maximum block
length via LV2_Buf_Size_Feature::get_sample_count().  Plugins that copy data
from audio inputs can require this feature to ensure they know how much space
is required for auxilliary buffers.  Note the minimum may be zero, this feature
is mainly useful to ensure a maximum is available.</p>

<p>All hosts SHOULD support this feature, since it is simple to support and
necessary for several relatively straightforward use cases.</p>
""" .

bufsz:fixedBlockLength
	a lv2:Feature ;
	lv2:documentation """
<p>A feature that indicates the host will always call LV2_Descriptor::run()
with the same value for sample_count.  If available,
LV2_Buf_Size_Feature::get_sample_count() must report this value for both min
and max.</p>

<p>Note that requiring this feature may severely limit the number of hosts
capable of running the plugin.</p>
""" .

bufsz:powerOf2BlockLength
	a lv2:Feature ;
	lv2:documentation """
<p>A feature that indicates the host will always call LV2_Descriptor::run()
with a power of two sample_count.  If available,
LV2_Buf_Size_Feature::get_sample_count() must report this value for both min
and max.  Note this feature does not guarantee the value is the same each call,
to ensure that the plugin must require both this feature and
bufsz:fixedBlockLength.</p>

<p>Note that requiring this feature may severely limit the number of hosts
capable of running the plugin.</p>
""" .