| Transform elements |
| ------------------ |
| |
| Transform elements transform input buffers to output buffers based |
| on the sink and source caps. |
| |
| typical transform elements include: |
| |
| - audio convertors (audioconvert, ...) |
| - video convertors (colorspace, videoscale, audioconvert, ...) |
| - filters (capfilter, colorbalance, |
| |
| The implementation of the transform element has to take care of |
| the following things: |
| |
| - efficient negotiation both up and downstream |
| - efficient buffer alloc and other buffer management |
| |
| Some transform elements can operate in different modes: |
| |
| - passthrough (no changes to buffers) |
| - in-place (changes made to incomming buffer) |
| - metadata changes only |
| |
| Depending on the mode of operation the buffer allocation strategy might change. |
| |
| |
| Negotiation |
| ----------- |
| |
| The transform element is configured to perform a specific transform in these |
| two situations: |
| |
| - new caps are received on the sink pad. |
| - new caps are received on the source pad when allocating an output buffer and |
| we can transform to these caps with the current input buffer. |
| |
| |
