AVR Freaks

Maybe Alexa is listening to the music and thinks she

hears her name, causing enough activity to interrupt

the music?

--Mike

Perhaps the Echo plays your instrumental music at 44.1kHz exactly, but the DAC in your audio dongle plays at 44.101kHz because they used a crappy crystal. Thus it will gradually empty any buffer down to zero bytes and that's when the dropouts occur.

Breaking & remaking the connection refills buffers again.

Anyone know how the Bluetooth A2DP stack works ?

My "2 clocks drifting apart" theory still applies in that condition.

Does the fault begin only after several hours of gapless playback; or just "being connected" without necessarily playing audio ?

If the audio stream stops & starts that may allow the stack to reinitialise and that would disprove my theory.

The slave should resynchronise it's local clock relative to the master's clock each time it receives a packet from the master.

In general, the procedure to allow for clock drift is something along the lines of

1) specify an upper limit for the crystal error

2) specify that the master must send some kind of packet to the slave at least once every so often

3)  the combination of 1) and 2) sets an upper limit on how far out the 2 clocks can be

4) the receiving device will widen its receive window by the amount in 3)

5) slave resynchronises each time it receives a packet

I think we're talking about different things here.

I was referring to 'resynchronise' as the slave updates its estimate of the offset betwen its clock and the master's clock, such that it knows (close enough) when to start listening for a packet from the master and so won't start missing packets due to clock drift. Not talking about 'resynchronise' in the sense of the audio stream.

BT is all time driven, based on timing slots, with the timing on the link based on the master's clock.

When slave recieves a packet, it can use the difference between when it thought the packet should arrive and when it actually arrived to update its estimate of this offset.

So I'm just saying, the fact that the link has been up for several hours should not be a reason in itself to start missing packets.

I don't know what the problem is.

Could be interference, but it's strange if it only ever happens several hours after connecting, but that could just be coincidence.

Could be a bug at one end.

Does the Alexa thing also use 2.4G wifi? Maybe it starts to do something over 2.4G wifi which takes priority over BT? Who knows.

Ideally, I guess it would be useful if  you could replace the device at each end in turn with a different device, and see if it makes any difference.