X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=hdmisdi.rst;h=a04c62ba3d09336680d80acb5d6936a2f75e90a8;hb=HEAD;hp=064fe85aef8c90cbc6ddf75ec846c31b6d1b14d6;hpb=faee0573b093e3e4d40c15ae50f1d882da4d8faa;p=nageru-docs

diff --git a/hdmisdi.rst b/hdmisdi.rst
index 064fe85..a04c62b 100644
--- a/hdmisdi.rst
+++ b/hdmisdi.rst
@@ -8,14 +8,14 @@ the stream on another PC, but for many uses, the end-to-end latency is
 too high, and you might not want to involve a full extra PC just for this
 anyway.
 
-Thus, since 1.5.0, Nageru supports using a spare output card for HDMI/SDI
+Thus, Nageru supports using a spare output card for HDMI/SDI
 output, turning it into a simple, reasonably low-latency audio/video switcher.
 
 
 Setting up HDMI/SDI output
 --------------------------
 
-Turning on HDMI/SDI output is simple; just right-click on the live view and
+To turn on HDMI/SDI output, right-click on the live view and
 select the output card. (Equivalently, you can access the same functionality
 from the *Video* menu in the regular menu bar, or you can give the
 *--output-card=* parameter on the command line.) Currently, this is supported
@@ -26,11 +26,23 @@ keep running just as before.
 A video mode will automatically be picked for you, favoring 59.94 fps if possible,
 but you can change the mode on-the-fly to something else if you'd like,
 as long as the resolution matches with what you've set up at program start.
-Note that whenever HDMI/SDI output is active, the output card will be the
+
+
+Unsynchronized HDMI/SDI output
+------------------------------
+
+By default, whenever HDMI/SDI output is active, the output card will be the
 master clock; you cannot change it to any of the input cards. This also means
 that the frame rate you choose here will determine the frame rate for the
 stream.
 
+In Nageru 2.1.0 or newer, you can use the flag --output-card-unsynchronized
+to counteract this (there is currently no way to do it from the GUI).
+This is for if you want just a monitor output without synchronizing
+your entire stream chain to the output card (ie., you want to keep
+some other camera as the master). Sound support is untested, and is
+probably going to crackle a fair bit.
+
 
 A note on latency
 -----------------
@@ -164,12 +176,14 @@ Audio and video queue lengths do not need to match exactly; the two streams
 and for HDMI/SDI output.
 
 
+.. _measuring-latency:
+
 Measuring latency
 .................
 
 In order to optimize latency, it can be useful to measure it, but for most
 people, it's hard to measure delays precisely enough to distinguish reliably
-between e.g. 70 and 80 milliseconds by eye alone. Nageru gives you some simple
+between e.g. 70 and 80 milliseconds by eye alone. Nageru gives you some
 tools that will help.
 
 The most direct is the flag *--print-video-latency*. This samples, for every
@@ -194,13 +208,21 @@ 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 <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