jsmad/decoder.cpp

#include "decoder.h"
#include <iostream>

Decoder::Decoder():
sampleRate(0),
channels(0),
cachedLength(0),
samplesPerFrame(0),
buffer(new uint8_t[BUFFER_LENGTH]),
cached(false),
synth(new mad_synth()),
stream(new mad_stream()),
frame(new mad_frame()),
context(0)
{
    for (int i = 0; i < BUFFER_LENGTH; ++i) {
        buffer[i] = 0;
    }
    
    mad_frame_init(frame);
    mad_stream_init(stream);
    mad_synth_init(synth);
    
    mad_stream_buffer(stream, buffer, 0);
    
    emscripten::val AudioContext = emscripten::val::global("AudioContext");
    if (!AudioContext.as<bool>()) {
        AudioContext = emscripten::val::global("webkitAudioContext");
    }
    
    context = AudioContext.new_();
}

Decoder::~Decoder()
{
    context.call<void>("close");
    
    mad_synth_finish(synth);
    mad_stream_finish(stream);
    mad_frame_finish(frame);
    
    delete synth;
    delete stream;
    delete frame;
    
    delete[] buffer;
}

void Decoder::addFragment(intptr_t bufferPtr, uint32_t length)
{
    std::cout << "Adding new fragment " << length << " bytes long" << std::endl;
    uint8_t* bf = (uint8_t(*))bufferPtr;
    uint64_t ol = stream->bufend - stream->buffer;
    
    for (int i = 0; i < length; ++i) {
        buffer[ol + i] = bf[i];
    }
    //free(bf);
    
    stream->bufend = stream->bufend + length;
    cached = false;
    framesLeft();
}

emscripten::val Decoder::decode(uint32_t count)
{
    emscripten::val ret = emscripten::val::undefined();
    
    int available = framesLeft(count);
    int success = 0;
    if (available > 0) {
        ret = context.call<emscripten::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<emscripten::val>("getChannelData", i);
        } 
        
        for (int i = 0; i < available; ++i) {
            int res = mad_frame_decode(frame, stream);
            
            if (res == 0) {
                ++success;
            } else {
                if (MAD_RECOVERABLE(stream->error)) {
                    
                    std::cout << "Unexpected error during the decoding process: " << mad_stream_errorstr(stream) << std::endl;
                    continue;
                } else {
                    break;
                }
            }
            
            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(success * samplesPerFrame + j), emscripten::val(value));
                }
            }
        }
        
        cachedLength -= available;
        std::cout << "Processed " << available << " frames, " << success << " successfully, last error " << mad_stream_errorstr(stream) << std::endl;
        
        if (cachedLength == 0) {
            framesLeft();
        }
    }
    
    return ret;
}

bool Decoder::hasMore() const
{
    return stream->bufend != stream->buffer && stream->error != MAD_ERROR_BUFLEN;
}

uint32_t Decoder::framesLeft(uint32_t max)
{
    if (!hasMore()) {
        return 0;
    }
    
    if (cached == false) {
        bool found = false;
        mad_stream probe;
        mad_header ph;
        initializeProbe(probe);
        mad_header_init(&ph);
        
        while (cachedLength < max) {
            if (mad_header_decode(&ph, &probe) == 0) {
                found = true;
                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) || samplesPerFrame != MAD_NSBSAMPLES(&ph) * 32) {
                        break;
                    }
                }
                if (probe.next_frame > probe.this_frame) {
                    ++cachedLength;
                }
            } else {
                if (!found) {
                    stream->next_frame = probe.next_frame;
                }
                std::cout << "framesLeft error: " << mad_stream_errorstr(&probe) << std::endl;
                if (!MAD_RECOVERABLE(probe.error)) {
                    break;
                }
            }
        }
        
        mad_header_finish(&ph);
        mad_stream_finish(&probe);
        std::cout << cachedLength << " frames are available for decoding" << std::endl;
        cached = true;
    }
    
    return std::min(cachedLength, max);
}

void Decoder::initializeProbe(mad_stream& probe)
{
    mad_stream_init(&probe);
    
    probe.buffer = stream->buffer;
    probe.bufend = stream->bufend;
    //probe.skiplen = stream->skiplen; 
    //probe.sync = stream->sync;
    //probe.freerate = stream->freerate;
    //probe.this_frame = stream->this_frame;
    probe.next_frame = stream->next_frame;
    //probe.ptr.byte = stream->ptr.byte;
    //probe.ptr.cache = stream->ptr.cache;
    //probe.ptr.cache = stream->ptr.cache;
    //probe.anc_ptr.byte = stream->anc_ptr.byte;
    //probe.anc_ptr.cache = stream->anc_ptr.cache;
    //probe.anc_ptr.cache = stream->anc_ptr.cache;
    //probe.anc_bitlen = stream->anc_bitlen;
    //probe.main_data = stream.main_data;
    //probe.md_len = stream.md_len;
    //probe.options = stream->options;
    //probe.error = stream->error;
}