Improve recording performance by recording directly to a file

Resources/oscilloscope/oscilloscope.html

@@ -139,7 +139,8 @@
         let externalBufferSize = 1920;
         let recording = false;
         let mediaRecorder = undefined;
-        let downloadCallback = undefined;
+        let sendVideoDataCallback = undefined;
+        let finishRecordingCallback = undefined;
         
         const toggleRecording = () => {
             recording = !recording;
@@ -148,19 +149,16 @@
                 const data = [];
                 const stream = canvas.captureStream(60);
                 mediaRecorder = new MediaRecorder(stream);
-                mediaRecorder.ondataavailable = (e) => data.push(e.data);
-                mediaRecorder.onstop = (e) => {
-                    const div = document.getElementById("buttonRow");
-                    var a = document.createElement("a");
-                    const video = new Blob(data, { type: "video/webm;codecs=h264" });
+                mediaRecorder.ondataavailable = (e) => {
                     var reader = new FileReader();
-                    reader.readAsDataURL(video);
+                    reader.readAsDataURL(e.data);
                     reader.onloadend = function() {
                         var dataUrl = reader.result;
                         var base64 = dataUrl.split(',')[1];
-                        downloadCallback(base64);
+                        sendVideoDataCallback(base64);
                     }
                 };
+                mediaRecorder.onstop = (e) => finishRecordingCallback();
                 mediaRecorder.start();
             } else {
                 mediaRecorder.stop();
@@ -242,8 +240,12 @@
             toggleFullscreen();
         });
         
-        downloadCallback = (base64) => {
-            Juce.getNativeFunction("downloadVideo")(base64);
+        finishRecordingCallback = () => {
+            Juce.getNativeFunction("finishRecording")();
+        };
+        
+        sendVideoDataCallback = (base64) => {
+            Juce.getNativeFunction("sendVideoData")(base64);
         };
     </script>
     

Source/components/VisualiserComponent.cpp

@@ -270,9 +270,7 @@ void VisualiserComponent::paintXY(juce::Graphics& g, juce::Rectangle<float> area
 }
 
 void VisualiserComponent::initialiseBrowser() {
-    if (recordingHalted != nullptr) {
-        recordingHalted();
-    }
+    haltRecording();
     oldBrowser = std::move(browser);
     if (oldBrowser != nullptr) {
         removeChildComponent(oldBrowser.get());
@@ -326,18 +324,18 @@ void VisualiserComponent::initialiseBrowser() {
         .withNativeFunction("isVisualiserOnly", [this](auto& var, auto complete) {
             complete(visualiserOnly);
         })
-        .withNativeFunction("downloadVideo", [this](const juce::Array<juce::var>& args, auto complete) {
-            juce::String base64 = args[0].toString();
+        .withNativeFunction("sendVideoData", [this](const juce::Array<juce::var>& args, auto complete) {
+            juce::FileOutputStream stream{tempVideoFile};
+            juce::Base64::convertFromBase64(stream, args[0].toString());
+            stream.flush();
+        })
+        .withNativeFunction("finishRecording", [this](auto& var, auto complete) {
             chooser = std::make_unique<juce::FileChooser>("Save video", juce::File::getSpecialLocation(juce::File::SpecialLocationType::userDesktopDirectory).getChildFile("osci-render.webm"), "*.webm");
             chooser->launchAsync(juce::FileBrowserComponent::saveMode,
-                [base64](const juce::FileChooser& chooser) {
+                [this](const juce::FileChooser& chooser) {
                     juce::File result = chooser.getResult();
                     if (result.getFullPathName().isNotEmpty()) {
-                        juce::FileOutputStream stream(result);
-                        stream.setPosition(0);
-                        stream.truncate();
-                        juce::Base64::convertFromBase64(stream, base64);
-                        stream.flush();
+                        tempVideoFile.moveFileTo(result);
                     }
                 });
         })
@@ -388,9 +386,19 @@ void VisualiserComponent::toggleRecording() {
     if (oldVisualiser) {
         return;
     }
+    tempVideoFile = juce::File::createTempFile(".webm");
     browser->emitEventIfBrowserIsVisible("toggleRecording", juce::var());
 }
 
+void VisualiserComponent::haltRecording() {
+    if (oldVisualiser) {
+        return;
+    }
+    if (recordingHalted != nullptr) {
+        recordingHalted();
+    }
+}
+
 void VisualiserComponent::resized() {
     if (!oldVisualiser) {
         browser->setBounds(getLocalBounds());
@@ -415,9 +423,7 @@ void VisualiserComponent::childChanged() {
 }
 
 void VisualiserComponent::popoutWindow() {
-    if (recordingHalted != nullptr) {
-        recordingHalted();
-    }
+    haltRecording();
     auto visualiser = new VisualiserComponent(sampleRateManager, consumerManager, settings, this, oldVisualiser);
     visualiser->settings.setLookAndFeel(&getLookAndFeel());
     visualiser->openSettings = openSettings;

Source/components/VisualiserComponent.h

@@ -43,6 +43,7 @@ public:
     void setVisualiserType(bool oldVisualiser);
     void handleAsyncUpdate() override;
     void toggleRecording();
+    void haltRecording();
 
     VisualiserComponent* parent = nullptr;
     VisualiserComponent* child = nullptr;
@@ -124,6 +125,7 @@ private:
     std::unique_ptr<juce::WebBrowserComponent> oldBrowser = nullptr;
     
     std::unique_ptr<juce::FileChooser> chooser;
+    juce::File tempVideoFile;
     
     void initialiseBrowser();
     void resetBuffer();