audio: rewrote audio cache to write to contiguous segments rather than one long file

Fixes issues with PCM file placement, optimizes some audio-based timeline
and cache operations, just generally a better approach.

app/widget/viewer/audiowaveformview.cpp

@@ -63,11 +63,13 @@ void AudioWaveformView::paintEvent(QPaintEvent *event)
 {
   QWidget::paintEvent(event);
 
+  if (!playback_) {
+    return;
+  }
+
   const AudioParams& params = playback_->GetParameters();
 
-  if (!playback_
-      || playback_->GetPCMFilename().isEmpty()
-      || !params.is_valid()) {
+  if (!params.is_valid()) {
     return;
   }
 
@@ -78,9 +80,9 @@ void AudioWaveformView::paintEvent(QPaintEvent *event)
     cached_waveform_ = QPixmap(size());
     cached_waveform_.fill(Qt::transparent);
 
-    QFile fs(playback_->GetPCMFilename());
+    QIODevice* fs = playback_->CreatePlaybackDevice();
 
-    if (fs.open(QFile::ReadOnly)) {
+    if (fs->open(QFile::ReadOnly)) {
 
       QPainter wave_painter(&cached_waveform_);
 
@@ -89,13 +91,13 @@ void AudioWaveformView::paintEvent(QPaintEvent *event)
 
       int drew = 0;
 
-      fs.seek(params.samples_to_bytes(ScreenToUnitRounded(0)));
+      fs->seek(params.samples_to_bytes(ScreenToUnitRounded(0)));
 
-      for (int x=0; x<width() && !fs.atEnd(); x++) {
+      for (int x=0; x<width() && !fs->atEnd(); x++) {
         int samples_len = ScreenToUnitRounded(x+1) - ScreenToUnitRounded(x);
         int max_read_size = params.samples_to_bytes(samples_len);
 
-        QByteArray read_buffer = fs.read(max_read_size);
+        QByteArray read_buffer = fs->read(max_read_size);
 
         // Detect whether we've reached EOF and recalculate sample count if so
         if (read_buffer.size() < max_read_size) {
@@ -117,9 +119,11 @@ void AudioWaveformView::paintEvent(QPaintEvent *event)
       cached_scale_ = GetScale();
       cached_scroll_ = GetScroll();
 
-      fs.close();
+      fs->close();
 
     }
+
+    delete fs;
   }
 
   QPainter p(this);

app/widget/viewer/viewer.cpp

@@ -204,8 +204,8 @@ void ViewerWidget::ConnectNodeInternal(ViewerOutput *n)
 
   UpdateStack();
 
+  waveform_view_->SetViewer(GetConnectedNode()->audio_playback_cache());
   if (GetConnectedTimelinePoints()) {
-    waveform_view_->SetViewer(GetConnectedNode()->audio_playback_cache());
     waveform_view_->ConnectTimelinePoints(GetConnectedTimelinePoints());
   }
 
@@ -512,23 +512,24 @@ void ViewerWidget::PushScrubbedAudio()
 {
   if (!IsPlaying() && Config::Current()["AudioScrubbing"].toBool()) {
     // Get audio src device from renderer
-    QString audio_fn = GetConnectedNode()->audio_playback_cache()->GetPCMFilename();
-    QFile audio_src(audio_fn);
+    AudioPlaybackCache::PlaybackDevice* audio_src = GetConnectedNode()->audio_playback_cache()->CreatePlaybackDevice();
 
-    if (audio_src.open(QFile::ReadOnly)) {
+    if (audio_src->open(QIODevice::ReadOnly)) {
       const AudioParams& params = GetConnectedNode()->audio_playback_cache()->GetParameters();
 
       // FIXME: Hardcoded scrubbing interval (20ms)
       int size_of_sample = params.time_to_bytes(rational(20, 1000));
 
       // Push audio
-      audio_src.seek(params.time_to_bytes(GetTime()));
-      QByteArray frame_audio = audio_src.read(size_of_sample);
+      audio_src->seek(params.time_to_bytes(GetTime()));
+      QByteArray frame_audio = audio_src->read(size_of_sample);
       AudioManager::instance()->SetOutputParams(params);
       AudioManager::instance()->PushToOutput(frame_audio);
 
-      audio_src.close();
+      audio_src->close();
     }
+
+    delete audio_src;
   }
 }
 
@@ -628,13 +629,11 @@ void ViewerWidget::FinishPlayPreprocess()
 {
   int64_t playback_start_time = ruler()->GetTime();
 
-  QString audio_fn = GetConnectedNode()->audio_playback_cache()->GetPCMFilename();
-  if (!audio_fn.isEmpty()) {
-    AudioManager::instance()->SetOutputParams(GetConnectedNode()->audio_playback_cache()->GetParameters());
-    AudioManager::instance()->StartOutput(audio_fn,
-                                          GetConnectedNode()->audio_playback_cache()->GetParameters().time_to_bytes(GetTime()),
-                                          playback_speed_);
-  }
+  AudioPlaybackCache* audio_cache = GetConnectedNode()->audio_playback_cache();
+  AudioManager::instance()->SetOutputParams(audio_cache->GetParameters());
+  AudioManager::instance()->StartOutput(audio_cache,
+                                        audio_cache->GetParameters().time_to_bytes(GetTime()),
+                                        playback_speed_);
 
   playback_timer_.Start(playback_start_time, playback_speed_, timebase_dbl());