View source for Ethersound latency

This page describes the latency of the Ethersound firmware used with different devices.

== Latency ==
The end-to-end latency of an Ethersound encoder and a Barix ES100spkr decoder heavily depends on the codec used.

=== VLSI based devices ===
On '''Exstreamer 1xx, Exstreamer 2xx and all Annuncicom devices in DHW: 2.xx ''' the end-to-end latency is approximately '''57ms'''. This is caused by large internal buffers in the VLSI codec.

=== Micronas based devices ===
The internal buffers of the Micronas codec are much smaller which also positively affects the latency.
The end-to-end-latency of the '''Exstreamer 1000, Annuncicom 100 (DHW: 1.xx), Annuncicom 200 (DHW: 1.xx) and Annuncicom 1000 (DHW: 1.xx)''' is only about '''6ms'''.

== Latency measurements ==

Both latencies were measured in the below described test. 

=== Test environment ===

The latency was measured with the following equipment:
* Digigiram ES220 as an input device
* another ES220 as a reference output device
* Exstreamer 100 as an output device (VLSI based device)
* Annuncicom 100 as an output device (Micronas based device)
* HP procurve 1700-8 switch where all devices were connected to

Both Barix devices were loaded with the version 00.03 of the Ethersound decoder module.

The input of the ES220 was fed with a 500Hz tone from a signal generator. The input, both output Barix devices as well as the reference ES220 device were monitored with an oscilloscope.

A trigger was set to capture the waveform after switching on the signal generator.

=== Test results ===
The below three diagrams show the results of the measurement. The top line (channel 4, green) is the clock source. Channels 1 (yellow), 2 (blue) and 3 (violet) are: the VLSI device (Exstreamer 100), the Micronas device (Annuncicom 100) and the reference ES220.

'''On the first diagram the 57.2ms latency of the VLSI decoder (Exstreamer 100) can be seen.'''

[[Image:vlsi_latency.png]]

'''The second screen shot shows the end-to-end latency using a Micronas based device Annuncicom 100. The latency is significantly lower - only 6ms.'''

[[Image:micronas_latency.png]]

'''The last picture shows the end-to-end delay using the reference ES220 device. The latency is 1.44ms.'''

[[Image:es220_latency.png]]