fix(audio): specify format for sounds and make sounds follow it

This should reduce the problem that some sounds are very silent and some are loud.

audio/format.md

@@ -0,0 +1,17 @@
+To keep sounds consistent a sound file should follow the parameters listed
+below.
+
+# Format
+
+Internally qTox needs PCM with signed 16Bit integers and a samplerate of
+48kHz and one channel (mono).
+
+You can use ffmpeg to create those files as follows:
+```
+ffmpeg -i notification.wav -f s16le -acodec pcm_s16le -ac 1 -ar 48000 notification.s16le.pcm
+```
+
+# Normalization
+
+All sound files should have their maximum at -1.0 dB.
+To normalize them correctly you can use Audacity with the "Normalize" plugin.

res.qrc

@@ -6,10 +6,10 @@
         <file alias="DejaVuSans.ttf">res/font/DejaVuSans.ttf</file>
     </qresource>
     <qresource prefix="/">
-        <file>audio/notification.pcm</file>
-        <file>audio/ToxIncomingCall.pcm</file>
-        <file>audio/ToxOutgoingCall.pcm</file>
-        <file>audio/ToxEndCall.pcm</file>
+        <file>audio/notification.s16le.pcm</file>
+        <file>audio/ToxIncomingCall.s16le.pcm</file>
+        <file>audio/ToxOutgoingCall.s16le.pcm</file>
+        <file>audio/ToxEndCall.s16le.pcm</file>
         <file>img/add.svg</file>
         <file>img/avatar_mask.svg</file>
         <file>img/contact.svg</file>

src/audio/audio.h

@@ -48,15 +48,15 @@ class Audio : public QObject
     {
         switch (s) {
         case Sound::Test:
-            return QStringLiteral(":/audio/notification.pcm");
+            return QStringLiteral(":/audio/notification.s16le.pcm");
         case Sound::NewMessage:
-            return QStringLiteral(":/audio/notification.pcm");
+            return QStringLiteral(":/audio/notification.s16le.pcm");
         case Sound::IncomingCall:
-            return QStringLiteral(":/audio/ToxIncomingCall.pcm");
+            return QStringLiteral(":/audio/ToxIncomingCall.s16le.pcm");
         case Sound::OutgoingCall:
-            return QStringLiteral(":/audio/ToxOutgoingCall.pcm");
+            return QStringLiteral(":/audio/ToxOutgoingCall.s16le.pcm");
         case Sound::CallEnd:
-            return QStringLiteral(":/audio/ToxEndCall.pcm");
+            return QStringLiteral(":/audio/ToxEndCall.s16le.pcm");
         }
         assert(false);
         return QString();
@@ -109,6 +109,7 @@ class Audio : public QObject
 
 protected:
     // Public default audio settings
+    // Samplerate for Tox calls and sounds
     static constexpr uint32_t AUDIO_SAMPLE_RATE = 48000;
     static constexpr uint32_t AUDIO_FRAME_DURATION = 20;
     static constexpr uint32_t AUDIO_FRAME_SAMPLE_COUNT_PER_CHANNEL =

src/audio/backend/openal.cpp

@@ -377,7 +377,7 @@ bool OpenAL::initOutput(const QString& deviceName)
 }
 
 /**
- * @brief Play a 44100Hz mono 16bit PCM sound from a file
+ * @brief Play a 48kHz mono 16bit PCM sound from a file
  *
  * @param[in] path the path to the sound file
  */
@@ -389,7 +389,7 @@ void OpenAL::playMono16Sound(const QString& path)
 }
 
 /**
- * @brief Play a 44100Hz mono 16bit PCM sound
+ * @brief Play a 48kHz mono 16bit PCM sound
  */
 void OpenAL::playMono16Sound(const QByteArray& data)
 {
@@ -408,11 +408,11 @@ void OpenAL::playMono16Sound(const QByteArray& data)
         alSourcei(alMainSource, AL_BUFFER, AL_NONE);
     }
 
-    alBufferData(alMainBuffer, AL_FORMAT_MONO16, data.constData(), data.size(), 44100);
+    alBufferData(alMainBuffer, AL_FORMAT_MONO16, data.constData(), data.size(), AUDIO_SAMPLE_RATE);
     alSourcei(alMainSource, AL_BUFFER, static_cast<ALint>(alMainBuffer));
     alSourcePlay(alMainSource);
 
-    int durationMs = data.size() * 1000 / 2 / 44100;
+    int durationMs = data.size() * 1000 / 2 / AUDIO_SAMPLE_RATE;
     QMetaObject::invokeMethod(&playMono16Timer, "start", Q_ARG(int, durationMs + 50));
 }