On Mon, Jun 13, 2016 at 01:47:13PM +0200, Richard Cochran wrote: > 3. ALSA support for tunable AD/DA clocks. The rate of the Listener's > DA clock must match that of the Talker and the other Listeners. > Either you adjust it in HW using a VCO or similar, or you do > adaptive sample rate conversion in the application. (And that is > another reason for *not* having a shared kernel buffer.) For the > Talker, either you adjust the AD clock to match the PTP time, or > you measure the frequency offset. Actually, we already have support for tunable clock-like HW elements, namely the dynamic posix clock API. It is trivial to write a driver for VCO or the like. I am just not too familiar with the latest high end audio devices. I have seen audio PLL/multiplier chips that will take, for example, a 10 kHz input and produce your 48 kHz media clock. With the right HW design, you can tell your PTP Hardware Clock to produce a 10000 PPS, and you will have a synchronized AVB endpoint. The software is all there already. Somebody should tell the ALSA guys about it. I don't know if ALSA has anything for sample rate conversion or not, but haven't seen anything that addresses distributed synchronized audio applications. Thanks, Richard -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
