Brian, I think your idea does work. I think the tricky bit to doing this really 
well is having a control loop that reacts quickly enough that we don’t have to 
be stuck with a giant buffer that adds undesirable latency, but then conversely 
a control loop that adapts at a slow enough rate and with small enough steps 
that we don’t introduce human perceptible audio artifacts. 

> On Mar 7, 2019, at 7:46 AM, Brian Padalino via USRP-users 
> <usrp-us...@lists.ettus.com> wrote:
> 
> On Wed, Mar 6, 2019 at 3:12 PM Marcus Müller <marcus.muel...@ettus.com 
> <mailto:marcus.muel...@ettus.com>> wrote:
> I've had rather longish discussions on how to solve this; essentially:
> for something that actually *solves* the issue (instead of postponing
> it), as Ian said, you'd need to have clock domain crossing ability.
> 
> Could message passing from the real-time blocks solve this issue in a 
> flexible way?
> 
> Imagine the following: blocks connected to actual hardware use the computer 
> wall clock to try to determine an average sample clock as it relates to the 
> CPU clock.  The USRP source block would be able to determine how many 
> samples/(sec of CPU clock) were coming in and Audio sink blocks would be able 
> to determine how many samples/(sec of CPU clock) were being consumed.  The 
> same idea for Audio sources and USRP sinks.  Since the blocking calls for 
> USRP or Audio blocks could be wrapped in a high precision timer, once any 
> initial buffering had been filled up, the rate should settle out.
> 
> The modified blocks could then send a message of actual sample rate to 
> whoever needed to listen, and the appropriate sample rate could be figured 
> out in the "resampling FIFO".
> 
> What am I missing?  Why won't this work?
> 
> Brian
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