convoLV2 is a LV2 plugin to convolve audio signals with zero latency.

It is a very basic plugin: Currently the only parameter is the Impulse-Response file and hence it is robust and efficient convolver.

The plugin comes in three variants:

• Mono: 1 channel in, 1 channel out. Mono IR file
• Mono To Stereo: 1 channel in, 2 channel out. Stereo IR file. (L, R)
• True Stereo: 2 in, 2 out. 4 channel IR file (L -> L, R -> R, L -> R, R -> L)

Excess channels in an IR file are ignored. If an IR file has insufficient channels for the required configuration, channel-assignment wraps around (modulo file channel count).

convoLV2's main use-case is cabinet-emulation and generic signal processing where latency matters.

For fancy reverb applications, see also IR.lv2

libzita-convolver is used to perform the convolution, libsndfile to read the impulse-response and libsamplerate to resample the IR if necessary.

convoLV2 was written to demonstrate new features of LV2 1.2.0 (back in 2012):

• http://lv2plug.in/ns/ext/buf-size/#powerOf2BlockLength - the plugin requires a blocksize that is a power of two.
• http://lv2plug.in/ns/ext/buf-size/#maxBlockLength - the plugin only works with blocksizes between 64 and 8192 samples per period.
• http://lv2plug.in/ns/ext/patch/ - allow a host to pass filenames to a plugin.
• http://lv2plug.in/ns/ext/worker/ - on/offline instances. Re-loading an IR file is performed in the background, making the plugin realtime safe.

It since serves as example code for those LV2 extensions.

While the convolution engine supports pre-delay, channel-mapping and per-channel gain settings, these parameters are currently not exposed in the LV2 interface (hack tip: they are supported in the LV2 DSP and saved as text in the plugin-state which can be directly edited).