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, 6 insertions, 5 deletions

diff --git a/audio/decode/dec_audio.c b/audio/decode/dec_audio.c
index b44216ec00..46009c6fdd 100644
--- a/audio/decode/dec_audio.c
+++ b/audio/decode/dec_audio.c
@@ -317,7 +317,9 @@ int audio_decode(struct dec_audio *d_audio, struct mp_audio_buffer *outbuf,
     double filter_multiplier = af_calc_filter_multiplier(d_audio->afilter);
 
     int prev_buffered = -1;
-    while (minsamples >= 0) {
+    int res = 0;
+    MP_STATS(d_audio, "start audio");
+    while (res >= 0 && minsamples >= 0) {
         int buffered = mp_audio_buffer_samples(outbuf);
         if (minsamples < buffered || buffered == prev_buffered)
             break;
@@ -343,11 +345,10 @@ int audio_decode(struct dec_audio *d_audio, struct mp_audio_buffer *outbuf,
          * of buffering in filters */
         huge_filter_buffer = 1;
 
-        int res = filter_n_bytes(d_audio, outbuf, decsamples);
-        if (res < 0)
-            return res;
+        res = filter_n_bytes(d_audio, outbuf, decsamples);
     }
-    return 0;
+    MP_STATS(d_audio, "end audio");
+    return res;
 }
 
 void audio_reset_decoding(struct dec_audio *d_audio)