<img src="/images/latency-chain.png" title="Latency chain" alt="Latency chain" />
<p>
- <em>Figure: Latency chain.</em>
- The numbers are an example for a typical PC. With professional gear and an
- optimized system the total roundtrip latency is usually lower. The important
+ <em>Figure: Latency chain.</em>
+ The numbers are an example for a typical PC. With professional gear and an
+ optimized system the total round-trip latency is usually lower. The important
point is that latency is always additive and a sum of many independent factors.
</p>
Processing latency is usually divided into <dfn>capture latency</dfn> (the time
it takes for the digitized audio to be available for digital processing, usually
one audio period), and <dfn>playback latency</dfn> (the time it takes for
- In practice, the combination of both matters. It is called <dfn>roundtrip
+ In practice, the combination of both matters. It is called <dfn>round-trip
latency</dfn>: the time necessary for a certain audio event to be captured,
processed and played back.
</p>
</p>
-<h2>Low Latency usecases</h2>
+<h2>Low Latency use cases</h2>
<p>
Low latency is <strong>not</strong> always a feature you want to have. It
comes with a couple of drawbacks: the most prominent is increased power
edge of the JACK graph (capture)?
</li>
<li>
- How long will it be until the data writen to port Ao or Bo arrives at the
+ How long will it be until the data written to port Ao or Bo arrives at the
edge of the JACK graph (playback)?
</li>
</ul>
<h2>Calibrating JACK Latency</h2>
<p>
Linux DSP guru Fons Adriaensen wrote a tool called <dfn>jack_delay</dfn>
- to accurately measure the roundtrip latency of a closed loop audio chain,
+ to accurately measure the round-trip latency of a closed loop audio chain,
with sub-sample accuracy. JACK itself includes a variant of this tool
called <dfn>jack_iodelay</dfn>.
</p>
</p>
<ol>
<li>Launch jackd with the configuration you want to test.</li>
- <li>Launch <kbd class="input">jack_delay</kbd> on the commandline.</li>
+ <li>Launch <kbd class="input">jack_delay</kbd> on the command line.</li>
<li>Make the appropriate connections between your jack ports so the loop is closed.</li>
<li>Adjust the playback and capture levels in your mixer.</li>
</ol>