comparison vamp-sdk/hostext/PluginChannelAdapter.h @ 64:9d3272c7db60

* Merge from host-factory-stuff branch: this adds several helper classes in
  the hostext directory that should make a host's life much easier.  This
  will become version 1.1 of the SDK, eventually.

+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    Vamp
+
+    An API for audio analysis and feature extraction plugins.
+
+    Centre for Digital Music, Queen Mary, University of London.
+    Copyright 2006 Chris Cannam.
+  
+    Permission is hereby granted, free of charge, to any person
+    obtaining a copy of this software and associated documentation
+    files (the "Software"), to deal in the Software without
+    restriction, including without limitation the rights to use, copy,
+    modify, merge, publish, distribute, sublicense, and/or sell copies
+    of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be
+    included in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+    NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
+    ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
+    CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+    WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+    Except as contained in this notice, the names of the Centre for
+    Digital Music; Queen Mary, University of London; and Chris Cannam
+    shall not be used in advertising or otherwise to promote the sale,
+    use or other dealings in this Software without prior written
+    authorization.
+*/
+
+#ifndef _VAMP_PLUGIN_CHANNEL_ADAPTER_H_
+#define _VAMP_PLUGIN_CHANNEL_ADAPTER_H_
+
+#include "PluginWrapper.h"
+
+namespace Vamp {
+
+namespace HostExt {
+
+/**
+ * PluginChannelAdapter is a Vamp plugin adapter that implements a
+ * policy for management of plugins that expect a different number of
+ * input channels from the number actually available in the source
+ * audio data.
+ *
+ * A host using PluginChannelAdapter may ignore the getMinChannelCount
+ * and getMaxChannelCount reported by the plugin, and still expect the
+ * plugin to run.
+ *
+ * PluginChannelAdapter implements the following policy:
+ *
+ * -- If the plugin supports the provided number of channels directly,
+ * PluginChannelAdapter will just run the plugin as normal.
+ *
+ * -- If the plugin only supports exactly one channel but more than
+ * one channel is provided, PluginChannelAdapter will use the mean of
+ * the channels.  This ensures that the resulting values remain within
+ * the same magnitude range as expected for mono data.
+ *
+ * -- If the plugin requires more than one channel but exactly one is
+ * provided, the provided channel will be duplicated across all the
+ * plugin input channels.
+ *
+ * If none of the above apply:
+ * 
+ * -- If the plugin requires more channels than are provided, the
+ * minimum acceptable number of channels will be produced by adding
+ * empty (zero valued) channels to those provided.
+ *
+ * -- If the plugin requires fewer channels than are provided, the
+ * maximum acceptable number of channels will be produced by
+ * discarding the excess channels.
+ *
+ * Hosts requiring a different channel policy from the above will need
+ * to implement it themselves, instead of using PluginChannelAdapter.
+ *
+ * Note that PluginChannelAdapter does not override the minimum and
+ * maximum channel counts returned by the wrapped plugin.  The host
+ * will need to be aware that it is using a PluginChannelAdapter, and
+ * be prepared to ignore these counts as necessary.  (This contrasts
+ * with the approach used in PluginInputDomainAdapter, which aims to
+ * make the host completely unaware of which underlying input domain
+ * is in fact in use.)
+ * 
+ * (The rationale for this is that a host may wish to use the
+ * PluginChannelAdapter but still discriminate in some way on the
+ * basis of the number of channels actually supported.  For example, a
+ * simple stereo audio host may prefer to reject plugins that require
+ * more than two channels on the grounds that doesn't actually
+ * understand what they are for, rather than allow the channel adapter
+ * to make a potentially meaningless channel conversion for them.)
+ *
+ * In every respect other than its management of channels, the
+ * PluginChannelAdapter behaves identically to the plugin that it
+ * wraps.  The wrapped plugin will be deleted when the wrapper is
+ * deleted.
+ */
+
+class PluginChannelAdapter : public PluginWrapper
+{
+public:
+    PluginChannelAdapter(Plugin *plugin); // I take ownership of plugin
+    virtual ~PluginChannelAdapter();
+
+    bool initialise(size_t channels, size_t stepSize, size_t blockSize);
+
+    FeatureSet process(const float *const *inputBuffers, RealTime timestamp);
+
+protected:
+    size_t m_blockSize;
+    size_t m_inputChannels;
+    size_t m_pluginChannels;
+    float **m_buffer;
+    const float **m_forwardPtrs;
+};
+
+}
+
+}
+
+#endif