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Re: [Discuss-gnuradio] question about overruns with simple flowgraph

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] question about overruns with simple flowgraph
Date: Thu, 08 Aug 2013 13:04:59 -0400
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On 08/08/2013 12:03 PM, Vanush Vaswani wrote:
Has there been any effort in using PTP to solve the two-clock problem (like Audinate's Dante)?

The two-clock problem exists due to the fact that the two *hardware* clocks involved here -- the audio subsystem, and the USRP aren't locked to each other, and aren't at exactly, precisely, the rate you think they are (the nature of oscillators).

Clock-skew (between source and sink) tends to get "absorbed" in buffering, but since buffering is a finite resource, occasionally leading to the audio subsystem saying "guys, I can't accept any more samples at the moment, my buffers are full". The way to "solve" this problem is to have a control-loop that allows you to fine-tune the rate that samples are delivered to the sink -- you need a "speed up a bit/slow down a bit" control message that occurs
  before things are about to get ugly.

Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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