audio: change playback speed directly in resampler

Although the libraries we use for resampling (libavresample and
libswresample) do not support changing sampelrate on the fly, this makes
it easier to make sure no audio buffers are implicitly dropped. In fact,
this commit adds additional code to drain the resampler explicitly.

Changing speed twice without feeding audio in-between made it crash
with libavresample inc ertain cases (libswresample is fine). This is
probably a libavresample bug. Hopefully this will be fixed, and also I
attempted to workaround the situation that crashes it. (It seems to
point in direction of random memory corruption, though.)

1 files changed, 2 insertions, 10 deletions

diff --git a/player/audio.c b/player/audio.c
index c4329f07c6..79be29a359 100644
--- a/player/audio.c
+++ b/player/audio.c
@@ -66,7 +66,6 @@ static int recreate_audio_filters(struct MPContext *mpctx)
 
     struct MPOpts *opts = mpctx->opts;
     struct af_stream *afs = mpctx->d_audio->afilter;
-    bool need_reinit = false;
 
     double speed = opts->playback_speed;
 
@@ -84,7 +83,7 @@ static int recreate_audio_filters(struct MPContext *mpctx)
             if (!af_control_any_rev(afs, AF_CONTROL_SET_PLAYBACK_SPEED, &speed))
             {
                 char *filter = method == AF_CONTROL_SET_PLAYBACK_SPEED
-                             ? "scaletempo" : "forcespeed";
+                             ? "scaletempo" : "lavrresample";
                 if (try_filter(mpctx, filter, "playback-speed", NULL) < 0)
                     return -1;
                 // Try again.
@@ -94,11 +93,6 @@ static int recreate_audio_filters(struct MPContext *mpctx)
                 method = AF_CONTROL_SET_PLAYBACK_SPEED;
             }
         }
-        // AF_CONTROL_SET_PLAYBACK_SPEED does not require reinitialization,
-        // while AF_CONTROL_SET_PLAYBACK_SPEED_RESAMPLE requires updating
-        // the samplerate on the resampler, and possibly inserting the
-        // resampler itself.
-        need_reinit |= (method == AF_CONTROL_SET_PLAYBACK_SPEED_RESAMPLE);
     } else {
         if (af_remove_by_label(afs, "playback-speed") < 0)
             return -1;
@@ -107,9 +101,7 @@ static int recreate_audio_filters(struct MPContext *mpctx)
         af_control_any_rev(afs, AF_CONTROL_SET_PLAYBACK_SPEED_RESAMPLE, &speed);
     }
 
-    need_reinit |= afs->initialized < 1;
-
-    if (need_reinit && af_init(afs) < 0) {
+    if (afs->initialized < 1 && af_init(afs) < 0) {
         MP_ERR(mpctx, "Couldn't find matching filter/ao format!\n");
         return -1;
     }