From 1c23a222b23f5598b041c84277a166cd0ac5f860 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?kleines=20Filmr=C3=B6llchen?= <filmroellchen@serenityos.org>
Date: Wed, 15 Jun 2022 21:43:07 +0200
Subject: [PATCH] AudioServer: Make hardware write buffer size flexible

This removes some old cruft to refactor the hardware buffer-related
datastructures into depending on a single constant, which determines the
number of samples per hardware buffer that the audio server mixes. This
is set to 1024 as before, so there are no functional changes.
---
 Userland/Services/AudioServer/Mixer.cpp | 17 ++++++-----------
 Userland/Services/AudioServer/Mixer.h   |  6 +++++-
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/Userland/Services/AudioServer/Mixer.cpp b/Userland/Services/AudioServer/Mixer.cpp
index 240e493cd9..89474d5873 100644
--- a/Userland/Services/AudioServer/Mixer.cpp
+++ b/Userland/Services/AudioServer/Mixer.cpp
@@ -20,8 +20,6 @@
 
 namespace AudioServer {
 
-u8 Mixer::m_zero_filled_buffer[4096];
-
 Mixer::Mixer(NonnullRefPtr<Core::ConfigFile> config)
     // FIXME: Allow AudioServer to use other audio channels as well
     : m_device(Core::File::construct("/dev/audio/0", this))
@@ -74,8 +72,7 @@ void Mixer::mix()
 
         active_mix_queues.remove_all_matching([&](auto& entry) { return !entry->client(); });
 
-        Audio::Sample mixed_buffer[1024];
-        auto mixed_buffer_length = (int)(sizeof(mixed_buffer) / sizeof(Audio::Sample));
+        Array<Audio::Sample, HARDWARE_BUFFER_SIZE> mixed_buffer;
 
         m_main_volume.advance_time();
 
@@ -89,8 +86,7 @@ void Mixer::mix()
             ++active_queues;
             queue->volume().advance_time();
 
-            for (int i = 0; i < mixed_buffer_length; ++i) {
-                auto& mixed_sample = mixed_buffer[i];
+            for (auto& mixed_sample : mixed_buffer) {
                 Audio::Sample sample;
                 if (!queue->get_next_sample(sample))
                     break;
@@ -103,13 +99,12 @@ void Mixer::mix()
         }
 
         if (m_muted) {
-            m_device->write(m_zero_filled_buffer, sizeof(m_zero_filled_buffer));
+            m_device->write(m_zero_filled_buffer.data(), static_cast<int>(m_zero_filled_buffer.size()));
         } else {
-            Array<u8, 4096> buffer;
+            Array<u8, HARDWARE_BUFFER_SIZE_BYTES> buffer;
             OutputMemoryStream stream { buffer };
 
-            for (int i = 0; i < mixed_buffer_length; ++i) {
-                auto& mixed_sample = mixed_buffer[i];
+            for (auto& mixed_sample : mixed_buffer) {
 
                 // Even though it's not realistic, the user expects no sound at 0%.
                 if (m_main_volume < 0.01)
@@ -128,7 +123,7 @@ void Mixer::mix()
 
             VERIFY(stream.is_end());
             VERIFY(!stream.has_any_error());
-            m_device->write(stream.data(), stream.size());
+            m_device->write(stream.data(), static_cast<int>(stream.size()));
         }
     }
 }
diff --git a/Userland/Services/AudioServer/Mixer.h b/Userland/Services/AudioServer/Mixer.h
index 840952b8f1..7647550b77 100644
--- a/Userland/Services/AudioServer/Mixer.h
+++ b/Userland/Services/AudioServer/Mixer.h
@@ -29,6 +29,10 @@ namespace AudioServer {
 // Headroom, i.e. fixed attenuation for all audio streams.
 // This is to prevent clipping when two streams with low headroom (e.g. normalized & compressed) are playing.
 constexpr double SAMPLE_HEADROOM = 0.95;
+// The size of the buffer in samples that the hardware receives through write() calls to the audio device.
+constexpr size_t HARDWARE_BUFFER_SIZE = 1024;
+// The hardware buffer size in bytes; there's two channels of 16-bit samples.
+constexpr size_t HARDWARE_BUFFER_SIZE_BYTES = HARDWARE_BUFFER_SIZE * 2 * sizeof(i16);
 
 class ConnectionFromClient;
 
@@ -129,7 +133,7 @@ private:
     NonnullRefPtr<Core::ConfigFile> m_config;
     RefPtr<Core::Timer> m_config_write_timer;
 
-    static u8 m_zero_filled_buffer[4096];
+    Array<u8, HARDWARE_BUFFER_SIZE_BYTES> m_zero_filled_buffer;
 
     void mix();
 };