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Issue 818112 link

Starred by 1 user
Status: Verified
Owner:
louiscollard@chromium.org
Closed: Apr 2018
EstimatedDays: ----
NextAction: ----
OS: ----
Pri: 3
Type: Feature



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Provide external signal for audio latency measurement

Project Member Reported by louiscollard@chromium.org, Mar 2 2018 
We would like to measure audio latency using a technique similar to the 'LED and oscilloscope test' described here:
https://source.android.com/devices/audio/latency_measure

This will enable us to measure output latency independent of input latency (and then infer input latency using existing loopback latency).

To implement this in a board-agnostic way, we will use a USB UART device, the latency of which we assume to be negligible.
Project Member

Comment 1 by bugdroid1@chromium.org, Mar 6 2018 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/audiotest/+/921fb15545204add8e741a9e352d8066a002d28c

commit 921fb15545204add8e741a9e352d8066a002d28c
Author: Louis Collard <louiscollard@chromium.org>
Date: Tue Mar 06 17:59:21 2018

[audiotest] Add option to loopback_latency to write zeros to a device when audio playback starts.

Additionally, prints reported output and input latencies individually.

This is intended to be used with a USB UART device, so that end-to-end
output latency can be measured using an oscilloscope.

This follows the technique described here (but using UART instead of an LED):
https://source.android.com/devices/audio/latency_measure

When audio output is measured from a loopback dongle, the full loopback
latency can be measured alongside the end-to-end output latency,
allowing any fixed latencies introduced by eg the DSP to be estimated.

BUG= chromium:818112 

Change-Id: I85a37d3a2b8665392ff2ccc897219e785af1be5b
Reviewed-on: https://chromium-review.googlesource.com/908255
Commit-Ready: Louis Collard <louiscollard@chromium.org>
Tested-by: Louis Collard <louiscollard@chromium.org>
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>

[modify] https://crrev.com/921fb15545204add8e741a9e352d8066a002d28c/src/loopback_latency.c

Comment 2 by louiscollard@chromium.org, Apr 11 2018

Status: Verified (was: Untriaged)
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