High performance is obtained by:
extremely light-weight links between plugins. Data can travel the pipeline with minimal overhead. Data passing between plugins only involves a pointer dereference in a typical pipeline.
providing a mechanism to directly work on the target memory. A plugin can for example directly write to the X server's shared memory space. Buffers can also point to arbitrary memory, such as a sound card's internal hardware buffer.
refcounting and copy on write minimize usage of memcpy. Sub-buffers efficiently split buffers into manageable pieces.
dedicated streaming threads, with scheduling handled by the kernel.
allowing hardware acceleration by using specialized plugins.
using a plugin registry with the specifications of the plugins so that the plugin loading can be delayed until the plugin is actually used.