When there is no data and the buffer is mmapable, try to mmap it. Unmap
again when clearing the buffers.
Use the mmaped data pointer of the buffer when processing.
Keep the passthrough flag up to date when we unset a port format or when
it changes.
We should only fill in the buffer data/fd when the ALLOC flag is set.
We should only take the passthrough input buffer as output when we are
in passthrough mode.
Copy the header metadata.
To activate:
PIPEWIRE_PROPS='{ video.adapt.converter = video.convert.ffmpeg }' build/src/examples/video-play
This makes it possible to start firefox with mjpg capture and then
video-play and it will decode the mjpeg transparently. Works for other
incompatible video formats as well, as long as they can be mmapped.
Ideally this should use something GPU accelerated and this is what the
vulkan converter will do.
