Update tracing.md: Add examples of reported and per-element latencies

markdown/design/tracing.md

@@ -240,9 +240,9 @@ Frontends can:
 
 ## latency
 
-- register to buffer and event flow
+- register to buffer, event and query flow
 - send custom event on buffer flow at source elements
-- catch events on event transfer at sink elements
+- catch events on event transfer at sink pads
 
 ## meminfo (not yet implemented)
 
@@ -446,6 +446,31 @@ audiotestsrc num-buffers=10 ! audioconvert ! volume volume=0.7 ! \
 autoaudiosink
 ```
 
+### print processing latencies for each element
+
+```
+GST_DEBUG="GST_TRACER:7" GST_TRACERS=latency(flags=element) gst-launch-1.0 \
+audiotestsrc num-buffers=10 ! audioconvert ! volume volume=0.7 ! \
+autoaudiosink
+```
+
+### print reported latencies for each element
+
+```
+GST_DEBUG="GST_TRACER:7" GST_TRACERS=latency(flags=reported) gst-launch-1.0 \
+audiotestsrc num-buffers=10 ! audioconvert ! volume volume=0.7 ! \
+autoaudiosink
+```
+
+### print all type of latencies for a pipeline
+
+```
+GST_DEBUG="GST_TRACER:7" \
+GST_TRACERS=latency(flags=pipeline+element+reported) gst-launch-1.0 \
+alsasrc num-buffers=20 ! flacenc ! identity ! \
+fakesink
+```
+
 ### Raise a warning if a leak is detected
 
 ```