emscripten audio: Added audio capture support.

src/audio/emscripten/SDL_emscriptenaudio.c

@@ -61,7 +61,6 @@ HandleAudioProcess(_THIS)
     Uint8 *buf = NULL;
     int byte_len = 0;
     int bytes = SDL_AUDIO_BITSIZE(this->spec.format) / 8;
-    int bytes_in = SDL_AUDIO_BITSIZE(this->convert.src_format) / 8;
 
     /* Only do something if audio is enabled */
     if (!SDL_AtomicGet(&this->enabled) || SDL_AtomicGet(&this->paused)) {
@@ -69,6 +68,8 @@ HandleAudioProcess(_THIS)
     }
 
     if (this->convert.needed) {
+        const int bytes_in = SDL_AUDIO_BITSIZE(this->convert.src_format) / 8;
+
         if (this->hidden->conv_in_len != 0) {
             this->convert.len = this->hidden->conv_in_len * bytes_in * this->spec.channels;
         }
@@ -133,9 +134,100 @@ HandleAudioProcess(_THIS)
     }
 }
 
+static void
+HandleCaptureProcess(_THIS)
+{
+    Uint8 *buf;
+    int buflen;
+
+    /* Only do something if audio is enabled */
+    if (!SDL_AtomicGet(&this->enabled) || SDL_AtomicGet(&this->paused)) {
+        return;
+    }
+
+    if (this->convert.needed) {
+        buf = this->convert.buf;
+        buflen = this->convert.len_cvt;
+    } else {
+        if (!this->hidden->mixbuf) {
+            this->hidden->mixbuf = (Uint8 *) SDL_malloc(this->spec.size);
+            if (!this->hidden->mixbuf) {
+                return;  /* oh well. */
+            }
+        }
+        buf = this->hidden->mixbuf;
+        buflen = this->spec.size;
+    }
+
+    EM_ASM_ARGS({
+        var numChannels = SDL2.capture.currentCaptureBuffer.numberOfChannels;
+        if (numChannels == 1) {  /* fastpath this a little for the common (mono) case. */
+            var channelData = SDL2.capture.currentCaptureBuffer.getChannelData(0);
+            if (channelData.length != $1) {
+                throw 'Web Audio capture buffer length mismatch! Destination size: ' + channelData.length + ' samples vs expected ' + $1 + ' samples!';
+            }
+            for (var j = 0; j < $1; ++j) {
+                setValue($0 + (j * 4), channelData[j], 'float');
+            }
+        } else {
+            for (var c = 0; c < numChannels; ++c) {
+                var channelData = SDL2.capture.currentCaptureBuffer.getChannelData(c);
+                if (channelData.length != $1) {
+                    throw 'Web Audio capture buffer length mismatch! Destination size: ' + channelData.length + ' samples vs expected ' + $1 + ' samples!';
+                }
+
+                for (var j = 0; j < $1; ++j) {
+                    setValue($0 + (((j * numChannels) + c) * 4), channelData[j], 'float');
+                }
+            }
+        }
+    }, buf, (this->spec.size / sizeof (float)) / this->spec.channels);
+
+    /* okay, we've got an interleaved float32 array in C now. */
+
+    if (this->convert.needed) {
+        SDL_ConvertAudio(&this->convert);
+    }
+
+    /* Send it to the app. */
+    (*this->spec.callback) (this->spec.userdata, buf, buflen);
+}
+
+
+
 static void
 Emscripten_CloseDevice(_THIS)
 {
+    EM_ASM_({
+        if ($0) {
+            if (SDL2.capture.silenceTimer !== undefined) {
+                clearTimeout(SDL2.capture.silenceTimer);
+            }
+            if (SDL2.capture.scriptProcessorNode !== undefined) {
+                SDL2.capture.scriptProcessorNode.disconnect();
+                SDL2.capture.scriptProcessorNode = undefined;
+            }
+            if (SDL2.capture.mediaStreamNode !== undefined) {
+                SDL2.capture.mediaStreamNode.disconnect();
+                SDL2.capture.mediaStreamNode = undefined;
+            }
+            if (SDL2.capture.silenceBuffer !== undefined) {
+                SDL2.capture.silenceBuffer = undefined
+            }
+            SDL2.capture = undefined;
+        } else {
+            if (SDL2.audio.scriptProcessorNode != undefined) {
+                SDL2.audio.scriptProcessorNode.disconnect();
+                SDL2.audio.scriptProcessorNode = undefined;
+            }
+            SDL2.audio = undefined;
+        }
+        if ((SDL2.audioContext !== undefined) && (SDL2.audio === undefined) && (SDL2.capture === undefined)) {
+            SDL2.audioContext.close();
+            SDL2.audioContext = undefined;
+        }
+    }, this->iscapture);
+
     SDL_free(this->hidden->mixbuf);
     SDL_free(this->hidden);
 }
@@ -144,11 +236,38 @@ static int
 Emscripten_OpenDevice(_THIS, void *handle, const char *devname, int iscapture)
 {
     SDL_bool valid_format = SDL_FALSE;
-    SDL_AudioFormat test_format = SDL_FirstAudioFormat(this->spec.format);
+    SDL_AudioFormat test_format;
     int i;
     float f;
     int result;
 
+    /* based on parts of library_sdl.js */
+
+    /* create context (TODO: this puts stuff in the global namespace...)*/
+    result = EM_ASM_INT({
+        if(typeof(SDL2) === 'undefined') {
+            SDL2 = {};
+        }
+        if (!$0) {
+            SDL2.audio = {};
+        } else {
+            SDL2.capture = {};
+        }
+
+        if (!SDL2.audioContext) {
+            if (typeof(AudioContext) !== 'undefined') {
+                SDL2.audioContext = new AudioContext();
+            } else if (typeof(webkitAudioContext) !== 'undefined') {
+                SDL2.audioContext = new webkitAudioContext();
+            }
+        }
+        return SDL2.audioContext === undefined ? -1 : 0;
+    }, iscapture);
+    if (result < 0) {
+        return SDL_SetError("Web Audio API is not available!");
+    }
+
+    test_format = SDL_FirstAudioFormat(this->spec.format);
     while ((!valid_format) && (test_format)) {
         switch (test_format) {
         case AUDIO_F32: /* web audio only supports floats */
@@ -173,34 +292,9 @@ Emscripten_OpenDevice(_THIS, void *handle, const char *devname, int iscapture)
     }
     SDL_zerop(this->hidden);
 
-    /* based on parts of library_sdl.js */
-
-    /* create context (TODO: this puts stuff in the global namespace...)*/
-    result = EM_ASM_INT_V({
-        if(typeof(SDL2) === 'undefined')
-            SDL2 = {};
-
-        if(typeof(SDL2.audio) === 'undefined')
-            SDL2.audio = {};
-
-        if (!SDL2.audioContext) {
-            if (typeof(AudioContext) !== 'undefined') {
-                SDL2.audioContext = new AudioContext();
-            } else if (typeof(webkitAudioContext) !== 'undefined') {
-                SDL2.audioContext = new webkitAudioContext();
-            } else {
-                return -1;
-            }
-        }
-        return 0;
-    });
-    if (result < 0) {
-        return SDL_SetError("Web Audio API is not available!");
-    }
-
     /* limit to native freq */
-    int sampleRate = EM_ASM_INT_V({
-        return SDL2.audioContext['sampleRate'];
+    const int sampleRate = EM_ASM_INT_V({
+        return SDL2.audioContext.sampleRate;
     });
 
     if(this->spec.freq != sampleRate) {
@@ -217,15 +311,71 @@ Emscripten_OpenDevice(_THIS, void *handle, const char *devname, int iscapture)
 
     SDL_CalculateAudioSpec(&this->spec);
 
-    /* setup a ScriptProcessorNode */
-    EM_ASM_ARGS({
-        SDL2.audio.scriptProcessorNode = SDL2.audioContext['createScriptProcessor']($1, 0, $0);
-        SDL2.audio.scriptProcessorNode['onaudioprocess'] = function (e) {
-            SDL2.audio.currentOutputBuffer = e['outputBuffer'];
-            Runtime.dynCall('vi', $2, [$3]);
-        };
-        SDL2.audio.scriptProcessorNode['connect'](SDL2.audioContext['destination']);
-    }, this->spec.channels, this->spec.samples, HandleAudioProcess, this);
+    if (iscapture) {
+        /* The idea is to take the capture media stream, hook it up to an
+           audio graph where we can pass it through a ScriptProcessorNode
+           to access the raw PCM samples and push them to the SDL app's
+           callback. From there, we "process" the audio data into silence
+           and forget about it. */
+
+        /* This should, strictly speaking, use MediaRecorder for capture, but
+           this API is cleaner to use and better supported, and fires a
+           callback whenever there's enough data to fire down into the app.
+           The downside is that we are spending CPU time silencing a buffer
+           that the audiocontext uselessly mixes into any output. On the
+           upside, both of those things are not only run in native code in
+           the browser, they're probably SIMD code, too. MediaRecorder
+           feels like it's a pretty inefficient tapdance in similar ways,
+           to be honest. */
+
+        EM_ASM_({
+            var have_microphone = function(stream) {
+                clearTimeout(SDL2.capture.silenceTimer);
+                SDL2.capture.silenceTimer = undefined;
+                SDL2.capture.mediaStreamNode = SDL2.audioContext.createMediaStreamSource(stream);
+                SDL2.capture.scriptProcessorNode = SDL2.audioContext.createScriptProcessor($1, $0, 1);
+                SDL2.capture.scriptProcessorNode.onaudioprocess = function(audioProcessingEvent) {
+                    audioProcessingEvent.outputBuffer.getChannelData(0).fill(0.0);
+                    SDL2.capture.currentCaptureBuffer = audioProcessingEvent.inputBuffer;
+                    Runtime.dynCall('vi', $2, [$3]);
+                };
+                SDL2.capture.mediaStreamNode.connect(SDL2.capture.scriptProcessorNode);
+                SDL2.capture.scriptProcessorNode.connect(SDL2.audioContext.destination);
+            };
+
+            var no_microphone = function(error) {
+                console.log('we DO NOT have a microphone! (' + error.name + ')...leaving silence callback running.');
+            };
+
+            /* we write silence to the audio callback until the microphone is available (user approves use, etc). */
+            SDL2.capture.silenceBuffer = SDL2.audioContext.createBuffer($0, $1, SDL2.audioContext.sampleRate);
+            SDL2.capture.silenceBuffer.getChannelData(0).fill(0.0);
+
+            var silence_callback = function() {
+                SDL2.capture.currentCaptureBuffer = SDL2.capture.silenceBuffer;
+                Runtime.dynCall('vi', $2, [$3]);
+            };
+
+            SDL2.capture.silenceTimer = setTimeout(silence_callback, $1 / SDL2.audioContext.sampleRate);
+
+            if ((navigator.mediaDevices !== undefined) && (navigator.mediaDevices.getUserMedia !== undefined)) {
+                navigator.mediaDevices.getUserMedia({ audio: true, video: false }).then(have_microphone).catch(no_microphone);
+            } else if (navigator.webkitGetUserMedia !== undefined) {
+                navigator.webkitGetUserMedia({ audio: true, video: false }, have_microphone, no_microphone);
+            }
+        }, this->spec.channels, this->spec.samples, HandleCaptureProcess, this);
+    } else {
+        /* setup a ScriptProcessorNode */
+        EM_ASM_ARGS({
+            SDL2.audio.scriptProcessorNode = SDL2.audioContext['createScriptProcessor']($1, 0, $0);
+            SDL2.audio.scriptProcessorNode['onaudioprocess'] = function (e) {
+                SDL2.audio.currentOutputBuffer = e['outputBuffer'];
+                Runtime.dynCall('vi', $2, [$3]);
+            };
+            SDL2.audio.scriptProcessorNode['connect'](SDL2.audioContext['destination']);
+        }, this->spec.channels, this->spec.samples, HandleAudioProcess, this);
+    }
+
     return 0;
 }
 
@@ -236,7 +386,6 @@ Emscripten_Init(SDL_AudioDriverImpl * impl)
     impl->OpenDevice = Emscripten_OpenDevice;
     impl->CloseDevice = Emscripten_CloseDevice;
 
-    /* only one output */
     impl->OnlyHasDefaultOutputDevice = 1;
 
     /* no threads here */
@@ -244,7 +393,7 @@ Emscripten_Init(SDL_AudioDriverImpl * impl)
     impl->ProvidesOwnCallbackThread = 1;
 
     /* check availability */
-    int available = EM_ASM_INT_V({
+    const int available = EM_ASM_INT_V({
         if (typeof(AudioContext) !== 'undefined') {
             return 1;
         } else if (typeof(webkitAudioContext) !== 'undefined') {
@@ -257,6 +406,18 @@ Emscripten_Init(SDL_AudioDriverImpl * impl)
         SDL_SetError("No audio context available");
     }
 
+    const int capture_available = available && EM_ASM_INT_V({
+        if ((typeof(navigator.mediaDevices) !== 'undefined') && (typeof(navigator.mediaDevices.getUserMedia) !== 'undefined')) {
+            return 1;
+        } else if (typeof(navigator.webkitGetUserMedia) !== 'undefined') {
+            return 1;
+        }
+        return 0;
+    });
+
+    impl->HasCaptureSupport = capture_available ? SDL_TRUE : SDL_FALSE;
+    impl->OnlyHasDefaultCaptureDevice = capture_available ? SDL_TRUE : SDL_FALSE;
+
     return available;
 }