core: do initial A-V sync by modifying audio stream

Add code to enforce matching pts with video when (re)starting the
audio stream, by either cutting away the first samples or inserting
silence at the beginning. New option -noinitial-audio-sync can be used
to disable this and return to old behavior.

1 files changed, 91 insertions, 12 deletions

diff --git a/mplayer.c b/mplayer.c
index 83c6328b5d..77350cad73 100644
--- a/mplayer.c
+++ b/mplayer.c
@@ -22,6 +22,8 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdbool.h>
+#include <math.h>
+
 #include "config.h"
 #include "talloc.h"
 
@@ -1790,6 +1792,7 @@ void reinit_audio_chain(struct MPContext *mpctx)
     }
     mpctx->mixer.audio_out = mpctx->audio_out;
     mpctx->mixer.volstep = volstep;
+    mpctx->syncing_audio = true;
     return;
 
 init_error:
@@ -2112,7 +2115,7 @@ static void adjust_sync(struct MPContext *mpctx, double frame_time)
 {
     current_module = "av_sync";
 
-    if (!mpctx->sh_audio)
+    if (!mpctx->sh_audio || mpctx->syncing_audio)
         return;
 
     double a_pts = written_audio_pts(mpctx) - mpctx->delay;
@@ -2133,6 +2136,67 @@ static void adjust_sync(struct MPContext *mpctx, double frame_time)
     mpctx->total_avsync_change += change;
 }
 
+#define ASYNC_PLAY_DONE -3
+static int audio_start_sync(struct MPContext *mpctx, int playsize)
+{
+    struct MPOpts *opts = &mpctx->opts;
+    sh_audio_t * const sh_audio = mpctx->sh_audio;
+    int res;
+
+    // Timing info may not be set without
+    res = decode_audio(sh_audio, 1);
+    if (res < 0)
+        return res;
+    double ptsdiff = written_audio_pts(mpctx) - mpctx->sh_video->pts -
+        mpctx->delay - audio_delay;
+    int bytes = ptsdiff * ao_data.bps / mpctx->opts.playback_speed;
+    bytes -= bytes % (ao_data.channels * af_fmt2bits(ao_data.format) / 8);
+
+    if (fabs(ptsdiff) > 300) // pts reset or just broken?
+        bytes = 0;
+
+    if (bytes <= 0) {
+        mpctx->syncing_audio = false;
+        while (1) {
+            int a = FFMIN(-bytes, FFMAX(playsize, 20000));
+            int res = decode_audio(sh_audio, a);
+            bytes += sh_audio->a_out_buffer_len;
+            if (bytes >= 0) {
+                memmove(sh_audio->a_out_buffer,
+                        sh_audio->a_out_buffer +
+                        sh_audio->a_out_buffer_len - bytes,
+                        bytes);
+                sh_audio->a_out_buffer_len = bytes;
+                if (res < 0)
+                    return res;
+                return decode_audio(sh_audio, playsize);
+            }
+            sh_audio->a_out_buffer_len = 0;
+            if (res < 0)
+                return res;
+        }
+    } else {
+        int fillbyte = 0;
+        if ((ao_data.format & AF_FORMAT_SIGN_MASK) == AF_FORMAT_US)
+            fillbyte = 0x80;
+        if (bytes >= playsize) {
+            /* This case could fall back to the one below with
+             * bytes = playsize, but then silence would keep accumulating
+             * in a_out_buffer if the AO accepts less data than it asks for
+             * in playsize. */
+            char *p = malloc(playsize);
+            memset(p, fillbyte, playsize);
+            playsize = mpctx->audio_out->play(p, playsize, 0);
+            free(p);
+            mpctx->delay += opts->playback_speed*playsize/(double)ao_data.bps;
+            return ASYNC_PLAY_DONE;
+        }
+        mpctx->syncing_audio = false;
+        decode_audio_prepend_bytes(sh_audio, bytes, fillbyte);
+        return decode_audio(sh_audio, playsize);
+    }
+}
+
 static int fill_audio_out_buffers(struct MPContext *mpctx)
 {
     struct MPOpts *opts = &mpctx->opts;
@@ -2167,10 +2231,20 @@ static int fill_audio_out_buffers(struct MPContext *mpctx)
     // Fill buffer if needed:
     current_module="decode_audio";
     t = GetTimer();
-    int res = decode_audio(sh_audio, playsize);
+
+    if (!opts->initial_audio_sync || (ao_data.format & AF_FORMAT_SPECIAL_MASK))
+        mpctx->syncing_audio = false;
+
+    int res;
+    if (mpctx->syncing_audio && mpctx->sh_video)
+        res = audio_start_sync(mpctx, playsize);
+    else
+        res = decode_audio(sh_audio, playsize);
     if (res < 0) {  // EOF, error or format change
         if (res == -2)
             format_change = true;
+        else if (res == ASYNC_PLAY_DONE)
+            return 1;
         else if (mpctx->d_audio->eof) {
             audio_eof = 1;
             int unitsize = ao_data.channels * af_fmt2bits(ao_data.format) / 8;
@@ -4181,7 +4255,8 @@ if(!mpctx->sh_audio && mpctx->d_audio->sh) {
 
 /*========================== PLAY AUDIO ============================*/
 
-if (mpctx->sh_audio && !mpctx->paused)
+if (mpctx->sh_audio && !mpctx->paused
+    && (!mpctx->restart_playback || !mpctx->sh_video))
     if (!fill_audio_out_buffers(mpctx))
 	// at eof, all audio at least written to ao
 	if (!mpctx->sh_video)
@@ -4234,14 +4309,9 @@ if(!mpctx->sh_video) {
       }
       if (frame_time < 0)
 	  mpctx->stop_play = AT_END_OF_FILE;
-      else {
-          if (mpctx->restart_playback) {
-              // Show this frame immediately, rest normally
-              mpctx->restart_playback = false;
-          } else {
-              mpctx->time_frame += frame_time / opts->playback_speed;
-              adjust_sync(mpctx, frame_time);
-          }
+      else if (!mpctx->restart_playback) {
+          mpctx->time_frame += frame_time / opts->playback_speed;
+          adjust_sync(mpctx, frame_time);
       }
   }
   if (mpctx->timeline) {
@@ -4287,7 +4357,8 @@ if(!mpctx->sh_video) {
            unsigned int pts_us = mpctx->last_time + mpctx->time_frame * 1e6;
            int duration = -1;
            double pts2 = mpctx->video_out->next_pts2;
-           if (pts2 != MP_NOPTS_VALUE && opts->correct_pts) {
+           if (pts2 != MP_NOPTS_VALUE && opts->correct_pts
+               && !mpctx->restart_playback) {
                // expected A/V sync correction is ignored
                double diff = (pts2 - mpctx->sh_video->pts);
                diff /= opts->playback_speed;
@@ -4309,6 +4380,14 @@ if(!mpctx->sh_video) {
                // For print_status - VO call finishing early is OK for sync
                mpctx->time_frame -= get_relative_time(mpctx);
            }
+           if (mpctx->restart_playback) {
+               mpctx->syncing_audio = true;
+               if (mpctx->sh_audio && !mpctx->paused)
+                   fill_audio_out_buffers(mpctx);
+               mpctx->restart_playback = false;
+               mpctx->time_frame = 0;
+               get_relative_time(mpctx);
+           }
            print_status(mpctx, MP_NOPTS_VALUE, true);
         }
         else