jsmad/decoder.cpp

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

Decoder::Decoder():
state(empty),
sampleRate(0),
channels(0),
cachedLength(0),
samplesPerFrame(0),
glue(new uint8_t[GLUE_LENGTH]),
cachedNext(NULL),
cachedThis(NULL),
cachedError(MAD_ERROR_NONE),
cached(false),
synth(new mad_synth()),
stream(new mad_stream()),
frame(new mad_frame()),
context(0),
pending()
{
    for (int i = 0; i < GLUE_LENGTH; ++i) {
        glue[i] = 0;
    }
    
    mad_frame_init(frame);
    mad_stream_init(stream);
    mad_synth_init(synth);
    
    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[] glue;
}

void Decoder::addFragment(const emscripten::val& array)
{
    uint32_t length = array["length"].as<uint32_t>();
    
    if (length < GLUE_LENGTH / 2) {
        std::cout << "Error: an attempt to add fragment smaller then half of the glue buffer, ignoring";
        return;
    }
    uint8_t* buffer = new uint8_t[length];
    
    for (int i = 0; i < length; ++i) {
        buffer[i] = array[std::to_string(i)].as<uint8_t>();
    }
    
    RawBuffer rb = {buffer, length};
    pending.push_back(rb);
    
    switch (state) {
        case empty:
            mad_stream_buffer(stream, buffer, length);
            
            for (int i = 0; i < GLUE_LENGTH/2; ++i) {
                glue[i] = buffer[length - GLUE_LENGTH/2 + i];
            }
            
            state = onBufferHalf;
            prepareNextBuffer();
            break;
        case onBufferHalf:
            for (int i = 0; i < GLUE_LENGTH/2; ++i) {
                glue[GLUE_LENGTH/2 + i] = buffer[i];
            }
            
            state = onBufferFull;
            break;
        case onBufferFull:
            break;
        case onGlueHalf:
            for (int i = 0; i < GLUE_LENGTH/2; ++i) {
                glue[GLUE_LENGTH/2 + i] = buffer[i];
            }
            
            state = onGlueFull;
            cached = false;
            prepareNextBuffer();
            break;
        case onGlueFull:
            break;
    }
}

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; success < available; ++i) {
            int res = mad_frame_decode(frame, stream);
            
            if (res != 0) {
                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));
                }
            }
            ++success;
        }
        
        cachedLength -= available;
        #if DEBUGGING
        std::cout << "Processed " << available << " frames, " << success << " successfully, last error " << mad_stream_errorstr(stream) << std::endl;
        #endif
        if (cachedLength == 0) {
            cached = false;
            prepareNextBuffer();
        }
    }
    
    return ret;
}

bool Decoder::hasMore() const
{
    if (pending.size() == 1) {
        return stream->error != MAD_ERROR_BUFLEN;
    } else {
        return true;
    }
}

uint32_t Decoder::framesLeft(uint32_t max)
{
    if (state == empty || state == onGlueHalf) {
        return 0;
    }
    
    if (cached == false) {
        mad_stream probe;
        mad_header ph;
        initializeProbe(probe);
        mad_header_init(&ph);
        sampleRate = 0;
        
        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) || samplesPerFrame != MAD_NSBSAMPLES(&ph) * 32) {
                        if (cachedLength > 0) {
                            #if DEBUGGING
                            std::cout << "sample rate " << sampleRate << " -> " << ph.samplerate << std::endl;
                            std::cout << "channels " << channels << " -> " << MAD_NCHANNELS(&ph) << std::endl;
                            std::cout << "samples per frame " << samplesPerFrame << " -> " << MAD_NSBSAMPLES(&ph) * 32 << std::endl;
                            #endif
                            probe.next_frame = probe.this_frame;
                            break;
                        }
                    }
                }
                if (probe.next_frame > probe.this_frame) {
                    ++cachedLength;
                }
            } else {
                #if DEBUGGING
                std::cout << "framesLeft error: " << mad_stream_errorstr(&probe) << std::endl;
                #endif
                if (!MAD_RECOVERABLE(probe.error)) {
                    break;
                }
            }
        }
        
        cachedNext = probe.next_frame;
        cachedThis = probe.this_frame;
        cachedError = probe.error;
        mad_header_finish(&ph);
        mad_stream_finish(&probe);
        #if DEBUGGING
        std::cout << cachedLength << " frames are available for decoding" << std::endl;
        #endif
        cached = true;
    }
    
    return std::min(cachedLength, max);
}

void Decoder::pullBuffer()
{
    if (cached == false) {
        std::cout << "Error in pullBuffer method!" << std::endl;
    }
    stream->this_frame = cachedThis;
    stream->next_frame = cachedNext;
    stream->error = cachedError;
}

void Decoder::changeBuffer()
{
    switch (state) {
        case empty:
            std::cout << "Wrong state on switchBuffer method - empty, aborting" << std::endl;
        case onBufferHalf:
            switchToGlue();
            state = onGlueHalf;
            break;
        case onBufferFull:
            switchToGlue();
            state = onGlueFull;
            break;
        case onGlueHalf:
            std::cout << "Wrong state on switchBuffer method - onGlueHalf, aborting" << std::endl;
            break;
        case onGlueFull:
            #if DEBUGGING
            std::cout << "Having another fragment " << pending[0].length << " bytes long" << std::endl;
            #endif
            
            switchBuffer(pending[0].ptr, pending[0].length);
            
            for (int i = 0; i < GLUE_LENGTH/2; ++i) {
                glue[i] = pending[0].ptr[pending[0].length - GLUE_LENGTH/2 + i];
            }
            
            state = onBufferHalf;
            
            if (pending.size() > 1) {
                for (int i = 0; i < GLUE_LENGTH/2; ++i) {
                    glue[GLUE_LENGTH/2 + i] = pending[1].ptr[i];
                }
                
                state = onBufferFull;
            }
    }
    
    cached = false;
}

void Decoder::prepareNextBuffer()
{
    bool shift;
    do {
        shift = false;
        framesLeft();
        if (cachedLength == 0 && state != empty && state != onGlueHalf) {
            pullBuffer();
            changeBuffer();
            shift = true;
        }
    } while (shift);
}

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;
}

void Decoder::switchToGlue()
{
    #if DEBUGGING
    std::cout << "Switching to glue" << std::endl;
    #endif
    switchBuffer(glue, GLUE_LENGTH);
    
    #if DEBUGGING
    std::cout << "Freeing the drained fragment" << std::endl;
    #endif
    delete[] pending[0].ptr;
    pending.pop_front();
}

void Decoder::switchBuffer(uint8_t* bufferPtr, uint32_t length)
{
    uint32_t left;
    
    if (stream->error != MAD_ERROR_BUFLEN) {
        std::cout << "WARNING: Switching buffers while the previous one is not drained, last error: " << mad_stream_errorstr(stream) << std::endl;
    }
    if (stream->next_frame != NULL) {
        left = stream->bufend - stream->next_frame;
    } else {
        std::cout << "WARNING: not supposed to happen" << std::endl;
    }
    
    if (left > GLUE_LENGTH / 2) {
        std::cout << "Error: bytes to read in the buffer are more then glue buffer can fit (" << left << ")" << std::endl;
        throw 1;
    }
    
    mad_stream_buffer(stream, bufferPtr + GLUE_LENGTH / 2 - left, length - (GLUE_LENGTH / 2 - left));
    stream->error = MAD_ERROR_NONE;
    
    while (mad_header_decode(&frame->header, stream) != 0 && stream->error != MAD_ERROR_BUFLEN) {}
}