BBuffer

A BBuffer references a chunk of shared memory where media data can be passed between applications and nodes. The control header for these buffers is passed through the use of a safer IPC mechanism, but the actual data these headers represent typically require a high data rate, and for the sake of maximizing performance, shared memory is the method by which the buffers are managed.

BBuffers originate at some BBufferProducer, which has a BBufferGroup that acts as a source of BBuffers (see BBufferConsumer::SetOutputBuffersFor()). BBuffers are sent through all participating nodes, possibly being sent down a long chain—much like a bucket brigade—until finally the node arrives at a node that chooses not to pass along the BBuffer any further, at which the buffer’s Recycle() function is called to return the buffer to the BBufferGroup’s store, where it gets reused by another batch of data.

An application or custom node can set up BBuffers that reference a specific area of memory, such as a low-level driver buffer, a BBitmap, or a BDirectWindow’s area of a frame buffer. This ability can provide for great optimization by avoiding unnecessary copy operations.

The BSmallBuffer class, derived from BBuffer, is used for very small buffers; they don’t go in BBufferGroups, and get handled specially to optimize performance.

Warning

BBuffer should never be subclassed, since they’re mostly owned and managed by the Media Server. Even if you create your own BBuffer, once you’ve called BBufferConsumer::SetOutputBuffersFor(), the “same” buffer received back by your BBufferConsumer may actually be another instance of the BBuffer class.