Henrik Austad wrote:
[...] As to moving samples from the buffer onto the network, one approach would be to wrap a set of samples and place it into a ready frame with headers and bits set and leave it in a buffer for the network layer to pick up.
The exact method here is not clear to me yet, I need to experiment, and probably send something off to the networking guys. But before I do that, I'd like to have a reasonable sane idea of how ALSA should handle this.
ALSA expects that the sound card hardware fetches samples whenever it needs them.
For USB and FireWire, there is a short queue of packets; the driver appends new packets whenever a bunch of older packets has been completed (as reported by an interrupt).
(This queue is separate from the ALSA ring buffer, which is then never accessed directly by hardware.)
The process of evening out the rate of samples is what traffic shaping and stream reservation will help you do (or enforce, ymmv), to some extent at least. The credit based shaper algorithm is designed to force bursty traffic into a steady stream.
In the case of USB and FireWire, the hardware already knows to send isochronous packets at a rate of 8 kHz.
A 'normal' NIC wouldn't be able to do this. Are there NICs that have a separate queue for isochronous packets? Or how else can this be handled?
Regards, Clemens