[vlc-commits] coreaudio: fix calculation when the clock sources are different

[Thomas Guillem]

vlc | branch: master | Thomas Guillem <thomas at gllm.fr> | Mon Mar 30 13:42:26 2020 +0200| [303d12153f67742ac21a31efb1eeb1f4aaa04f08] | committer: Thomas Guillem

coreaudio: fix calculation when the clock sources are different

As MONOTONIC is defined by POSIX to be the one that ticks during sleep while
mach absolute time does not.

For now (and for 3.0) vlc_tick_now() has the same source than the mach one.

> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=303d12153f67742ac21a31efb1eeb1f4aaa04f08
---

 modules/audio_output/coreaudio_common.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/modules/audio_output/coreaudio_common.c b/modules/audio_output/coreaudio_common.c
index 900616a8aa..5f8a633bee 100644
--- a/modules/audio_output/coreaudio_common.c
+++ b/modules/audio_output/coreaudio_common.c
@@ -243,9 +243,10 @@ ca_TimeGet(audio_output_t *p_aout, vlc_tick_t *delay)
         return -1;
     }
 
-    const vlc_tick_t i_render_time_us =
-        HostTimeToTick(p_sys, p_sys->i_render_host_time);
-    const vlc_tick_t i_render_delay = i_render_time_us - vlc_tick_now();
+    uint64_t i_render_delay_host_time = p_sys->i_render_host_time
+                                      - mach_absolute_time();
+    const vlc_tick_t i_render_delay =
+        HostTimeToTick(p_sys, i_render_delay_host_time);
 
     *delay = ca_GetLatencyLocked(p_aout) + i_render_delay;
     lock_unlock(p_sys);
@@ -307,9 +308,14 @@ ca_Play(audio_output_t * p_aout, block_t * p_block, vlc_tick_t date)
          * first (non-silence/zero) frame is rendered by the render callback.
          * Once the rendering is truly started, the date can be ignored. */
 
-        const vlc_tick_t first_render_time = date - ca_GetLatencyLocked(p_aout);
-        p_sys->i_first_render_host_time =
-            TickToHostTime(p_sys, first_render_time);
+        /* We can't convert date to host time directly since the clock source
+         * may be different (MONOTONIC vs continue during sleep). The solution
+         * is to convert it to a relative time and then add it to
+         * mach_absolute_time() */
+        const vlc_tick_t first_render_delay = date - vlc_tick_now()
+                                            - ca_GetLatencyLocked(p_aout);
+        p_sys->i_first_render_host_time
+            = mach_absolute_time() + TickToHostTime(p_sys, first_render_delay);
     }
 
     do