annotate vamp-sdk/hostext/PluginChannelAdapter.h @ 59:fa79c4ec847d host-factory-stuff

* Put hostext stuff in the HostExt sub-namespace
* Tidy up system-specific stuff in PluginLoader
* Make PluginLoader return a deletion-notifying wrapper which permits the
  library to be unloaded when no longer in use
* Add PluginChannelAdapter
* Make vamp-simple-host use PluginChannelAdapter, and use the PluginLoader
  for plugin-running task.  Also some other enhancements to host

/* -*- 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 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.
 */

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