From aa8ac249a0f178acc307410c74cb2f2429dec54a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=AE=D1=80=D0=B8=D0=B9=20=D0=93=D1=83=D0=B1=D0=B8=D1=87?=
 <blue@macaw.me>
Date: Sat, 29 Dec 2018 21:08:22 +0300
Subject: [PATCH] possible to decode portions, possible to find out how much is
 still available for one stream decoding

---
 index.html  | 36 ++++++++++++++++++------------
 wrapper.cpp | 64 ++++++++++++++++++++++++++++++++---------------------
 wrapper.h   |  9 +++++---
 3 files changed, 67 insertions(+), 42 deletions(-)

diff --git a/index.html b/index.html
index 3166bd1..2930041 100644
--- a/index.html
+++ b/index.html
@@ -12,41 +12,49 @@
   <script src="wrapper.js"></script>
     <input type="file" id="file" name="file" />
   <script>
+    var time = 0;
+    var ctx = new AudioContext();
+    ctx.suspend();
+    var decoder;
     function onChange(e) {
         var file = e.target.files[0];
         
         var reader = new FileReader();
         reader.onload = function(e) {
+            decoder = new Module.Decoder();
             var buffer = reader.result;
             var src = new Uint8Array(buffer);
             var ptr = Module._malloc(buffer.byteLength);
             var arr = new Uint8Array(Module.HEAPU8.buffer, ptr, buffer.byteLength);
-            var ctx = new AudioContext();
-            var time = 0;
             arr.set(src, 0);
             
-            var decoder = new Module.Decoder();
             decoder.addFragment(ptr, buffer.byteLength);
-            
-            while (decoder.hasMore()) {
-                var audio = decoder.decode(1);
-                if (audio === undefined) {
-                    if (decoder.hasMore() === false) {
-                        break;
-                    }
-                }
+            schedule();
+            ctx.resume();
+        }
+        reader.readAsArrayBuffer(file);
+        
+    }
+    
+    function schedule() {
+        if (decoder.hasMore()) {
+            var audio = decoder.decode(50);
+            if (audio) {
                 var source = ctx.createBufferSource();
                 source.buffer = audio;
                 source.connect(ctx.destination);
                 source.start(time);
                 time += audio.duration;
+                
+                setTimeout(schedule, Math.floor(audio.duration * 200));
+            } else {
+                decoder.delete();
             }
-            
+        } else {
             decoder.delete();
         }
-        reader.readAsArrayBuffer(file);
-        
     }
+    
     document.getElementById("file").addEventListener("change", onChange, false);
   </script>
   </body>
diff --git a/wrapper.cpp b/wrapper.cpp
index 71e690a..8446acd 100644
--- a/wrapper.cpp
+++ b/wrapper.cpp
@@ -1,5 +1,6 @@
 #include "wrapper.h"
 #include <string> 
+#include <iostream>
 
 MadHeader * mad_header_create()
 {
@@ -74,6 +75,7 @@ Decoder::Decoder():
     sampleRate(0),
     channels(0),
     cachedLength(0),
+    samplesPerFrame(0),
     currentBuffer(0),
     currentBufferLength(0),
     synth(),
@@ -121,29 +123,36 @@ void Decoder::addFragment(intptr_t bufferPtr, unsigned long length)
     framesLeft();
 }
 
-emscripten::val Decoder::decode(int count)
+emscripten::val Decoder::decode(uint32_t count)
 {
     emscripten::val ret = emscripten::val::undefined();
-    int result = -1;
     
     int available = framesLeft(count);
     if (available > 0) {
-        ret = context.call<val>("createBuffer", channels, synth.pcm.length, sampleRate);
-    }
-    
-    if (result == 0) {
-        mad_synth_frame(&synth, &frame);
-        ret = context.call<val>("createBuffer", synth.pcm.channels, synth.pcm.length, synth.pcm.samplerate);
-        for (int i = 0; i < synth.pcm.channels; ++i) {
-            emscripten::val chan = ret.call<val>("getChannelData", i);
-            mad_fixed_t* sChan = synth.pcm.samples[i];
-            for (int j = 0; j < synth.pcm.length; ++j) {
-                float value = mad_f_todouble(sChan[j]);
-                chan.set(std::to_string(j), val(value));
+        ret = context.call<val>("createBuffer", channels, available * samplesPerFrame, sampleRate);
+        
+        std::vector<emscripten::val> chans(channels, emscripten::val::undefined());
+        for (int i = 0; i < channels; ++i) {
+            chans[i] = ret.call<val>("getChannelData", i);
+        } 
+        
+        for (int i = 0; i < available; ++i) {
+            mad_frame_decode(&frame, &stream);
+            mad_synth_frame(&synth, &frame);
+            
+            for (int j = 0; j < samplesPerFrame; ++j) {
+                for (int k = 0; k < channels; ++k) {
+                    float value = mad_f_todouble(synth.pcm.samples[k][j]);
+                    chans[k].set(std::to_string(i * samplesPerFrame + j), val(value));
+                }
             }
         }
         
-        return ret;
+        cachedLength -= available;
+        
+        if (cachedLength == 0) {
+            framesLeft();
+        }
     }
     
     return ret;
@@ -158,38 +167,43 @@ bool Decoder::hasMore() const
     return stream.error != MAD_ERROR_BUFLEN;
 }
 
-uint64_t Decoder::framesLeft(uint64_t max)
+uint32_t Decoder::framesLeft(uint32_t max)
 {
     if (currentBuffer == 0) {
         return 0;
     }
     
-    if (!stream.sync) {
-        int result = mad_stream_sync(&stream);
-        if (result != 0) {
-            return 0;
-        }
-    }
-    
     if (cachedLength == 0) {
         mad_stream probe;
         mad_header ph;
         mad_stream_init(&probe);
         mad_header_init(&ph);
+        
+        mad_stream_buffer(&probe, currentBuffer, currentBufferLength);
         mad_stream_skip(&probe, stream.skiplen);
-        while (probe.error != MAD_ERROR_BUFLEN || cachedLength < max) {
+        
+        while (cachedLength < max) {
             if (mad_header_decode(&ph, &probe) == 0) {
                 if (sampleRate == 0) {
                     sampleRate = ph.samplerate;
                     channels = MAD_NCHANNELS(&ph);
+                    samplesPerFrame = MAD_NSBSAMPLES(&ph) * 32; //not sure why 32, it's in libmad source
                 } else {
-                    if (sampleRate != ph.samplerate || channels != MAD_NCHANNELS(&ph)) {
+                    if (sampleRate != ph.samplerate || channels != MAD_NCHANNELS(&ph) || samplesPerFrame != MAD_NSBSAMPLES(&ph) * 32) {
                         break;
                     }
                 }
                 ++cachedLength;
+            } else {
+                if (!MAD_RECOVERABLE(probe.error)) {
+                    std::cout << "framesLeft::" << probe.error << std::endl;
+                    break;
+                }
             }
         }
+        
+        mad_header_finish(&ph);
+        mad_stream_finish(&probe);
     } 
     
     return std::min(cachedLength, max);
diff --git a/wrapper.h b/wrapper.h
index eb6c366..7dc7d67 100644
--- a/wrapper.h
+++ b/wrapper.h
@@ -124,14 +124,15 @@ public:
     ~Decoder();
     
     void addFragment(intptr_t bufferPtr, unsigned long length);
-    val decode(int count);
+    val decode(uint32_t count = UINT32_MAX);
     bool hasMore() const;
-    uint64_t framesLeft(uint64_t max = UINT64_MAX);
+    uint32_t framesLeft(uint32_t max = UINT32_MAX);
     
 private:
     uint32_t sampleRate;
     uint8_t channels;
-    uint64_t cachedLength;
+    uint32_t cachedLength;
+    uint16_t samplesPerFrame;
     unsigned char* currentBuffer;
     unsigned long currentBufferLength;
     
@@ -236,6 +237,7 @@ EMSCRIPTEN_BINDINGS(jsmad) {
     function("mad_stream_init", &mad_stream_init, allow_raw_pointers());
     function("mad_stream_finish", &mad_stream_finish, allow_raw_pointers());
     function("mad_stream_buffer", &mad_stream_buffer, allow_raw_pointers());
+    function("mad_stream_sync", &mad_stream_sync, allow_raw_pointers());
     
     class_<mad_pcm>("mad_pcm");
     class_<MadPCM, base<mad_pcm>>("MadPCM")
@@ -259,6 +261,7 @@ EMSCRIPTEN_BINDINGS(jsmad) {
         .constructor<>()
         .function("addFragment", &Decoder::addFragment)
         .function("hasMore", &Decoder::hasMore)
+        .function("framesLeft", &Decoder::framesLeft)
         .function("decode", &Decoder::decode);
 }