player: add a --dump-stats option

This collects statistics and other things. The option dumps raw data
into a file. A script to visualize this data is included too.

Litter some of the player code with calls that generate these
statistics.

In general, this will be helpful to debug timing dependent issues, such
as A/V sync problems. Normally, one could argue that this is the task of
a real profiler, but then we'd have a hard time to include extra
information like audio/video PTS differences. We could also just
hardcode all statistics collection and processing in the player code,
but then we'd end up with something like mplayer's status line, which
was cluttered and required a centralized approach (i.e. getting the data
to the status line; so it was all in mplayer.c). Some players can
visualize such statistics on OSD, but that sounds even more complicated.
So the approach added with this commit sounds sensible.

The stats-conv.py script is rather primitive at the moment and its
output is semi-ugly. It uses matplotlib, so it could probably be
extended to do a lot, so it's not a dead-end.

1 files changed, 8 insertions, 0 deletions

diff --git a/DOCS/man/en/options.rst b/DOCS/man/en/options.rst
index 9e139c0578..d46ba0e959 100644
--- a/DOCS/man/en/options.rst
+++ b/DOCS/man/en/options.rst
@@ -759,6 +759,14 @@ OPTIONS
     Time in milliseconds to recognize two consecutive button presses as a
     double-click (default: 300).
 
+``--dump-stats=<filename>``
+    Write certain statistics to the given file. The file is truncated on
+    opening. The file will contain raw samples, each with a timestamp. To
+    make this file into a readable, the script ``TOOLS/stats-conv.py`` can be
+    used (which currently displays it as a graph).
+
+    This option is useful for debugging only.
+
 ``--dvbin=<options>``
     Pass the following parameters to the DVB input module, in order to
     override the default ones: