From 07aba86b37887c0aef7ea90af250fcf19062369b Mon Sep 17 00:00:00 2001
From: wm4 <wm4@nowhere>
Date: Fri, 15 Aug 2014 23:52:42 +0200
Subject: audio: add a mode to insert silence on severe A/V desync

This is probably a stupid idea, but it can't be denied that this
actually allows playing video without larger desync, even if video is
too slow.
---
 player/audio.c | 21 +++++++++++++++++----
 player/core.h  |  2 ++
 2 files changed, 19 insertions(+), 4 deletions(-)

(limited to 'player')

diff --git a/player/audio.c b/player/audio.c
index abb81f987c..3a691fed09 100644
--- a/player/audio.c
+++ b/player/audio.c
@@ -384,6 +384,10 @@ void fill_audio_out_buffers(struct MPContext *mpctx, double endpts)
         return; // try again next iteration
     }
 
+    struct mp_audio out_format = {0};
+    ao_get_format(mpctx->ao, &out_format);
+    double play_samplerate = out_format.rate / opts->playback_speed;
+
     // If audio is infinitely fast, somehow try keeping approximate A/V sync.
     if (mpctx->audio_status == STATUS_PLAYING && ao_untimed(mpctx->ao) &&
         mpctx->video_status != STATUS_EOF && mpctx->delay > 0)
@@ -402,6 +406,19 @@ void fill_audio_out_buffers(struct MPContext *mpctx, double endpts)
         playsize = MPMAX(1, playsize + skip); // silence will be prepended
     }
 
+    if (opts->insert_silence) {
+        float S = 0.5;
+        if (!mpctx->paused && mpctx->audio_status == STATUS_PLAYING &&
+            mpctx->last_av_difference - mpctx->insert_silence > S)
+            mpctx->insert_silence += S;
+
+        if (mpctx->insert_silence > 0) {
+            int samples = MPMIN(playsize, play_samplerate * mpctx->insert_silence);
+            mp_audio_buffer_prepend_silence(mpctx->ao_buffer, samples);
+            mpctx->insert_silence -= samples / play_samplerate;
+        }
+    }
+
     int status = AD_OK;
     if (playsize > mp_audio_buffer_samples(mpctx->ao_buffer)) {
         status = audio_decode(d_audio, mpctx->ao_buffer, playsize);
@@ -470,10 +487,6 @@ void fill_audio_out_buffers(struct MPContext *mpctx, double endpts)
     bool partial_fill = false;
     int playflags = 0;
 
-    struct mp_audio out_format = {0};
-    ao_get_format(mpctx->ao, &out_format);
-    double play_samplerate = out_format.rate / opts->playback_speed;
-
     if (endpts != MP_NOPTS_VALUE) {
         double samples = (endpts - written_audio_pts(mpctx) - mpctx->audio_delay)
                          * play_samplerate;
diff --git a/player/core.h b/player/core.h
index 594f105668..2530e8acd2 100644
--- a/player/core.h
+++ b/player/core.h
@@ -260,6 +260,8 @@ typedef struct MPContext {
     double delay;
     // AV sync: time until next frame should be shown
     double time_frame;
+    // Optional/additional AV sync compensation if video is too slow.
+    double insert_silence;
     // Set to true some time after a new frame has been shown, and it turns out
     // that this frame was the last one before video ends.
     bool playing_last_frame;
-- 
cgit v1.2.3