Ticket #7496: pulse-latency-001.patch

libs/libmyth/audiooutputpulse.cpp

@@ -552 +552 @@
     else
         pa_cvolume_reset(&volume_control, audio_channels);
 
-    // set myth sizes and pa buffer metrics
-    fragment_size = (float)sample_rate * 0.020f * // 20msec
-        (float)(audio_bits / 8 * audio_channels);
-    soundcard_buffer_size = 16 * fragment_size;
-    buffer_settings.maxlength = soundcard_buffer_size;
-    buffer_settings.tlength = fragment_size * 4;
-    buffer_settings.prebuf = (uint32_t)-1;
-    buffer_settings.minreq = (uint32_t)-1;
-    VERBOSE(VB_AUDIO, LOC + fn_log_tag +
-            QString("fragment size %1, soundcard buffer size %2")
-            .arg(fragment_size).arg(soundcard_buffer_size));
-
     int flags = PA_STREAM_INTERPOLATE_TIMING
         | PA_STREAM_AUTO_TIMING_UPDATE
         | PA_STREAM_NO_REMAP_CHANNELS
-        | PA_STREAM_NO_REMIX_CHANNELS;
+        | PA_STREAM_NO_REMIX_CHANNELS
+        | PA_STREAM_ADJUST_LATENCY;
+
+    // request pa buffer metrics
+    pa_buffer_attr buffer_settings;
+    buffer_settings.tlength = pa_usec_to_bytes(80000, &sample_spec);
+                              // request 80msec total buffer
+    buffer_settings.prebuf = buffer_settings.tlength / 4;
+                             // limit size of pre-buffer before play starts
+    buffer_settings.maxlength = (uint32_t)-1;
+    buffer_settings.minreq = (uint32_t)-1;
+    VERBOSE(VB_AUDIO+VB_EXTRA, LOC +
+        QString("PulseAudio buffer settings requested: maxlength %1, tlength %2,"
+                " prebuf %3, minreq %4").arg(buffer_settings.maxlength)
+                .arg(buffer_settings.tlength).arg(buffer_settings.prebuf)
+                .arg(buffer_settings.minreq));
+
     pa_stream_connect_playback(pstream, NULL, &buffer_settings,
                                (pa_stream_flags_t)flags, &volume_control, NULL);
     pa_context_state_t cstate;
@@ -605 +609 @@
                 }
         }
     }
-    return (connected && !failed);
+    if (connected && !failed)
+    {
+        const pa_buffer_attr *buffer_metrics = pa_stream_get_buffer_attr(pstream);
+        VERBOSE(VB_AUDIO+VB_EXTRA, LOC +
+            QString("PulseAudio buffer metrics - maxlength %1, tlength %2, prebuf %3, minreq %4")
+            .arg(buffer_metrics->maxlength).arg(buffer_metrics->tlength)
+            .arg(buffer_metrics->prebuf).arg(buffer_metrics->minreq));
+
+        // set myth sizes
+        fragment_size = buffer_metrics->minreq;
+        soundcard_buffer_size = buffer_metrics->tlength;
+        VERBOSE(VB_AUDIO, LOC + fn_log_tag +
+            QString("Myth fragment size %1, soundcard buffer size %2")
+            .arg(fragment_size).arg(soundcard_buffer_size));
+        return true;
+    }
+    return false;
 }
 
 void AudioOutputPulseAudio::FlushStream(const char *caller)

libs/libmyth/audiooutputpulse.h

@@ -67 +67 @@
     pa_sample_spec          sample_spec;
     pa_channel_map          channel_map;
     pa_cvolume              volume_control;
-    pa_buffer_attr          buffer_settings;
+
 };
+
 #endif
 
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