X-Git-Url: https://git.sesse.net/?p=nageru-docs;a=blobdiff_plain;f=hdmisdi.rst;h=f6f032cf48a29df3c27cb9e6a4b8359a2242d6d2;hp=064fe85aef8c90cbc6ddf75ec846c31b6d1b14d6;hb=2eeb492b65ccbb2e2439d9f772ebdc64f70d40ea;hpb=faee0573b093e3e4d40c15ae50f1d882da4d8faa diff --git a/hdmisdi.rst b/hdmisdi.rst index 064fe85..f6f032c 100644 --- a/hdmisdi.rst +++ b/hdmisdi.rst @@ -164,6 +164,8 @@ Audio and video queue lengths do not need to match exactly; the two streams and for HDMI/SDI output. +.. _measuring-latency: + Measuring latency ................. @@ -194,13 +196,21 @@ lowest and highest will be printed. Do note that the measurement is still done over a single *output* frame; it is *not* a measurement over the last 100 output frames, even though the statistics are only printed every 100th. +For more precise measurements, you can use Prometheus metrics to get percentiles +for all of these points, which will measure over all frames (over a one-minute +window). This yields more precise information than sampling every 100 frames, +but setting up Prometheus and a graphic tool is a bit more work, and usually not +worth it for simple measurement. For more information, see :doc:`monitoring`. + Another trick that can be useful in some situations is *looping* your signal, ie., connecting your output back into your input. This allows you to measure delays that don't happen within Nageru itself, like any external converters, delays in the input driver, etc.. (It can also act as a sanity check to make sure your A/V chain passes the signal through without quality degradation, if you first set up a static picture as a signal and then switch to the loop -input to verify that the signal stays stable without color shifts e.g. [#]_) +input to verify that the signal stays stable without color e.g. shifts [#]_. +See the section on :doc:`the frame analyzer ` for other ways of +debugging signal integrity.) For this, the *timecode output* is useful; you can turn it on from the Video menu, or through the command-line flag *--timecode-stream*. (You can also