mirror of
https://github.com/cookiengineer/audacity
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103 lines
4.8 KiB
Plaintext
103 lines
4.8 KiB
Plaintext
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Backward Compatibility Statement for Vamp Plugin SDK version 2.0
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================================================================
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Plugin binary compatibility
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---------------------------
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Version 2.0 of the Vamp plugin binary interface is backward compatible
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with version 1.0.
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A plugin that was compiled and (statically) linked using version 1.x
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of the SDK should load and run without modification in a host that was
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compiled and linked using version 2.0 of the SDK.
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A plugin that was compiled and (statically) linked using version 2.0
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of the SDK should load and run in a host that was compiled and linked
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using version 1.x of the SDK. However, the 1.x host will be unable to
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see any durations that the plugin specifies for its returned features,
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as there was no support for duration in version 1 of the Vamp plugin
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interface.
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Plugin/host version discrimination
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----------------------------------
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A Vamp plugin library receives the Vamp SDK version number for the
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host as the first argument to its vampGetPluginDescriptor function.
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It may use this information to provide different behaviour depending
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on the version of the host.
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For example, the plugin may structure its outputs differently in older
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hosts that do not support feature duration. Or, if the plugins rely
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on version 2.0 features, the library could make itself invisible to
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older hosts (returning no plugin descriptors).
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The version argument passed to vampGetPluginDescriptor will be 1 for
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Vamp 1.x hosts or 2 for Vamp 2.0 hosts. (Plugin libraries should
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behave as for version 2 if passed a version number greater than 2.)
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Plugin SDK library compatibility
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--------------------------------
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For plugin code, version 2.0 of the Vamp plugin SDK is source
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compatible but not library ABI compatible with version 1.x.
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Plugins written for version 1.x should compile and link without
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modification using version 2.0. Plugins dynamically linked against
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version 1.x SDK libraries will need to be rebuilt if they are to work
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with version 2.0 libraries. To avoid dynamic library resolution
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issues, it is generally preferable to link the SDK statically when
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distributing binary plugins.
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Host SDK library compatibility
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------------------------------
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For host code, version 2.0 of the Vamp plugin SDK is neither source
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nor binary compatible with version 1.x.
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The host SDK header include location has moved for version 2.0; hosts
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should now only include headers from the vamp-hostsdk/ include
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directory -- the vamp-sdk/ directory is reserved for inclusion in
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plugin code only. There is also no longer a separate subdirectory for
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hostext headers.
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Hosts written for version 1.x will therefore need to have their
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#include directives updated as follows:
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Old New
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<vamp-sdk/PluginBase.h> <vamp-hostsdk/PluginBase.h>
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<vamp-sdk/Plugin.h> <vamp-hostsdk/Plugin.h>
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<vamp-sdk/RealTime.h> <vamp-hostsdk/RealTime.h>
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<vamp-sdk/hostext/PluginLoader.h> <vamp-hostsdk/PluginLoader.h>
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<vamp-sdk/hostext/PluginBufferingAdapter.h> <vamp-hostsdk/PluginBufferingAdapter.h>
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<vamp-sdk/hostext/PluginChannelAdapter.h> <vamp-hostsdk/PluginChannelAdapter.h>
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<vamp-sdk/hostext/PluginInputDomainAdapter.h> <vamp-hostsdk/PluginInputDomainAdapter.h>
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<vamp-sdk/PluginHostAdapter.h> <vamp-hostsdk/PluginHostAdapter.h>
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For most hosts, these should be the only changes necessary; the actual
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code remains the same.
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Hosts that incorporate plugin code
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----------------------------------
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One of the changes in this version of the SDK is that separate
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top-level C++ namespaces are used for classes compiled into plugins
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(the _VampPlugin namespace) and hosts (the _VampHost namespace), to
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avoid any confusion between host and plugin namespaces in unusual
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linkage situations (as the host and plugin SDKs contain many of the
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same classes, there is a risk that the wrong class may be picked up by
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a stupid dynamic linker in cases where the host and plugin SDK
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versions do not match). This additional namespace is added and opened
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silently in a manner that is transparent in most circumstances, and
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neither plugin nor host authors will normally need to know about it.
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However, hosts that directly incorporate code from plugins, for
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example to provide functionality that is the same as those plugins
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without having to explicitly load them, will find that they cannot
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resolve plugin symbols at link time because of this namespace
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mismatch. To avoid this, you may define the preprocessor symbol
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_VAMP_PLUGIN_IN_HOST_NAMESPACE when compiling the plugin code in the
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context of the host, to ensure that both host and plugin code exist
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within the same namespace.
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(If your host does this, why not make it load the plugins dynamically
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instead using the normal Vamp plugin loader method? There are many
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advantages to that.)
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