core: Rewrite some of the A/V sync related code

Notable functionality changes:
* Timing change between any two frames is now accurately limited to
  1/10 of their nominal distance. Previous code did not always use the
  correct duration.
* The status line now keeps showing the same A-V sync value from one
  video frame change to the next. Previously it kept recalculating
  the value using a new audio position but the same video position
  when the status line was updated between video frames. This
  incorrectly showed the video losing sync with audio.
* The status line now displays actual measured A-V difference in
  autosync mode too. The previous code displayed values that
  completely ignored real timing in autosync mode, showing 0 A-V
  difference even when video was significantly behind audio due to
  inadequate decoding speed. The new behavior can make the shown A-V
  values appear more unstable if the audio out has unreliable delay
  measurements (the most likely reason to use autosync), but this is a
  display change rather than a timing quality change.
* Autosync mode now tries to adjust timing by the amount of time
  vo_flip() calls take, so the calls start earlier and finish at the
  time the frame should be shown. Previously non-autosync mode
  adjusted for this but autosync did not.
* The warning about the system being too slow to decode the video in
  realtime is now displayed in autosync mode too.

1 files changed, 20 insertions, 0 deletions

diff --git a/mp_core.h b/mp_core.h
index a346c75dce..c9a843a78e 100644
--- a/mp_core.h
+++ b/mp_core.h
@@ -1,6 +1,8 @@
 #ifndef MPLAYER_MP_CORE_H
 #define MPLAYER_MP_CORE_H
 
+#include <stdbool.h>
+
 #include "options.h"
 #include "mixer.h"
 #include "subreader.h"
@@ -76,6 +78,9 @@ typedef struct MPContext {
     // struct.
     int num_buffered_frames;
 
+    // Show a video frame as quickly as possible without trying to adjust
+    // for AV sync. Used when starting a file or after seeking.
+    bool update_video_immediately;
     // AV sync: the next frame should be shown when the audio out has this
     // much (in seconds) buffered data left. Increased when more data is
     // written to the ao, decreased when moving to the next frame.
@@ -84,6 +89,17 @@ typedef struct MPContext {
     double delay;
     // AV sync: time until next frame should be shown
     float time_frame;
+    // How long the last vo flip() call took. Used to adjust timing with
+    // the goal of making flip() calls finish (rather than start) at the
+    // specified time.
+    float last_vo_flip_duration;
+    // How much video timing has been changed to make it match the audio
+    // timeline. Used for status line information only.
+    double total_avsync_change;
+    // A-V sync difference when last frame was displayed. Kept to display
+    // the same value if the status line is updated at a time where no new
+    // video frame is shown.
+    double last_av_difference;
 
     // Timestamp from the last time some timing functions read the
     // current time, in (occasionally wrapping) microseconds. Used
@@ -118,6 +134,10 @@ typedef struct MPContext {
     // step this many frames, then pause
     int step_frames;
 
+    // Set after showing warning about decoding being too slow for realtime
+    // playback rate. Used to avoid showing it multiple times.
+    bool drop_message_shown;
+
 #ifdef CONFIG_DVDNAV
     struct mp_image *nav_smpi; ///< last decoded dvdnav video image
     unsigned char *nav_buffer;   ///< last read dvdnav video frame