From 5bbc1d44bfcad3d6e8e3489c337219a8b43e181c Mon Sep 17 00:00:00 2001
From: Geoffrey McRae <geoff@hostfission.com>
Date: Fri, 28 Jan 2022 12:08:58 +1100
Subject: [PATCH] [client] audio/pw: get the period size to determine when to
 start audio

Previously this was hardcoded to 100ms which is far too high in most
instances, instead we get the initial period size and use whichever is
greater out of 50ms or the period size.

The idea is to reduce the amount of time it takes for the latency to
come down after initial stream start.
---
 client/audiodevs/PipeWire/pipewire.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/client/audiodevs/PipeWire/pipewire.c b/client/audiodevs/PipeWire/pipewire.c
index eb726c5d..27d26898 100644
--- a/client/audiodevs/PipeWire/pipewire.c
+++ b/client/audiodevs/PipeWire/pipewire.c
@@ -104,6 +104,16 @@ static void pipewire_onPlaybackProcess(void * userdata)
   if (pw.playback.rateMatch && pw.playback.rateMatch->size > 0)
     frames = min(frames, pw.playback.rateMatch->size);
 
+  // stream was started just to get the initial period size
+  if (pw.playback.startFrames == -1)
+  {
+    pw.playback.startFrames = frames;
+    pw_stream_set_active(pw.playback.stream, false);
+    sbuf->datas[0].chunk->size = 0;
+    pw_stream_queue_buffer(pw.playback.stream, pbuf);
+    return;
+  }
+
   frames = pw.playback.pullFn(dst, frames);
   if (!frames)
   {
@@ -209,7 +219,7 @@ static void pipewire_playbackSetup(int channels, int sampleRate,
   pw.playback.sampleRate  = sampleRate;
   pw.playback.stride      = sizeof(float) * channels;
   pw.playback.pullFn      = pullFn;
-  pw.playback.startFrames = maxLatencyFrames;
+  pw.playback.startFrames = -1;
 
   pw_thread_loop_lock(pw.thread);
   pw.playback.stream = pw_stream_new_simple(
@@ -247,11 +257,13 @@ static void pipewire_playbackSetup(int channels, int sampleRate,
       PW_ID_ANY,
       PW_STREAM_FLAG_AUTOCONNECT |
       PW_STREAM_FLAG_MAP_BUFFERS |
-      PW_STREAM_FLAG_RT_PROCESS  |
-      PW_STREAM_FLAG_INACTIVE,
+      PW_STREAM_FLAG_RT_PROCESS,
       params, 1);
 
   pw_thread_loop_unlock(pw.thread);
+
+  while(pw.playback.startFrames == -1)
+    pw_thread_loop_wait(pw.thread);
 }
 
 static bool pipewire_playbackStart(int framesBuffered)
@@ -268,7 +280,8 @@ static bool pipewire_playbackStart(int framesBuffered)
     switch (pw.playback.state)
     {
       case STREAM_STATE_INACTIVE:
-        if (framesBuffered >= pw.playback.startFrames)
+        if (framesBuffered >= max(pw.playback.startFrames,
+              pw.playback.sampleRate / 20)) //50ms
         {
           pw_stream_set_active(pw.playback.stream, true);
           pw.playback.state = STREAM_STATE_ACTIVE;