mp3_utils.cpp

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#include "stdafx.h"

using namespace bitreader_helper;

static unsigned extract_header_bits(const t_uint8 p_header[4],unsigned p_base,unsigned p_bits)
{
    assert(p_base+p_bits<=32);
    return (unsigned) extract_bits(p_header,p_base,p_bits);
}

namespace {

    class header_parser
    {
    public:
        header_parser(const t_uint8 p_header[4]) : m_bitptr(0) 
        {
            memcpy(m_header,p_header,4);
        }
        unsigned read(unsigned p_bits)
        {
            unsigned ret = extract_header_bits(m_header,m_bitptr,p_bits);
            m_bitptr += p_bits;
            return ret;
        }
    private:
        t_uint8 m_header[4];
        unsigned m_bitptr;
    };
}

typedef t_uint16 uint16;

static const uint16 bitrate_table_l1v1[16]  = {  0, 32, 64, 96,128,160,192,224,256,288,320,352,384,416,448,  0};
static const uint16 bitrate_table_l2v1[16]  = {  0, 32, 48, 56, 64, 80, 96,112,128,160,192,224,256,320,384,  0};
static const uint16 bitrate_table_l3v1[16]  = {  0, 32, 40, 48, 56, 64, 80, 96,112,128,160,192,224,256,320,  0};
static const uint16 bitrate_table_l1v2[16]  = {  0, 32, 48, 56, 64, 80, 96,112,128,144,160,176,192,224,256,  0};
static const uint16 bitrate_table_l23v2[16] = {  0,  8, 16, 24, 32, 40, 48, 56, 64, 80, 96,112,128,144,160,  0};
static const uint16 sample_rate_table[] = {11025,12000,8000};

unsigned mp3_utils::QueryMPEGFrameSize(const t_uint8 p_header[4])
{
    TMPEGFrameInfo info;
    if (!ParseMPEGFrameHeader(info,p_header)) return 0;
    return info.m_bytes;
}

bool mp3_utils::ParseMPEGFrameHeader(TMPEGFrameInfo & p_info,const t_uint8 p_header[4])
{
    enum {MPEG_LAYER_1 = 3, MPEG_LAYER_2 = 2, MPEG_LAYER_3 = 1};
    enum {_MPEG_1 = 3, _MPEG_2 = 2, _MPEG_25 = 0};

    header_parser parser(p_header);
    if (parser.read(11) != 0x7FF) return false;
    unsigned mpeg_version = parser.read(2);
    unsigned layer = parser.read(2);
    unsigned protection = parser.read(1);
    unsigned bitrate_index = parser.read(4);
    unsigned sample_rate_index = parser.read(2);
    if (sample_rate_index == 3) return false;//reserved
    unsigned paddingbit = parser.read(1);
    int paddingdelta = 0;
    parser.read(1);//private
    unsigned channel_mode = parser.read(2);
    parser.read(2);//channel_mode_extension
    parser.read(1);//copyright
    parser.read(1);//original
    parser.read(2);//emphasis

    unsigned bitrate = 0,sample_rate = 0;

    switch(layer)
    {
    default:
        return false;
    case MPEG_LAYER_3:
        paddingdelta = paddingbit ? 1 : 0;
        
        p_info.m_layer = 3;
        switch(mpeg_version)
        {
        case _MPEG_1:
            p_info.m_duration = 1152;
            bitrate = bitrate_table_l3v1[bitrate_index];
            break;
        case _MPEG_2:
        case _MPEG_25:
            p_info.m_duration = 576;
            bitrate = bitrate_table_l23v2[bitrate_index];
            break;
        default:
            return false;
        }
    
        break;
    case MPEG_LAYER_2:
        paddingdelta = paddingbit ? 1 : 0;
        p_info.m_duration = 1152;
        p_info.m_layer = 2;
        switch(mpeg_version)
        {
        case _MPEG_1:
            bitrate = bitrate_table_l2v1[bitrate_index];
            break;
        case _MPEG_2:
        case _MPEG_25:
            bitrate = bitrate_table_l23v2[bitrate_index];
            break;
        default:
            return false;
        }
        break;
    case MPEG_LAYER_1:
        paddingdelta = paddingbit ? 4 : 0;
        p_info.m_duration = 384;
        p_info.m_layer = 1;
        switch(mpeg_version)
        {
        case _MPEG_1:
            bitrate = bitrate_table_l1v1[bitrate_index];
            break;
        case _MPEG_2:
        case _MPEG_25:
            bitrate = bitrate_table_l1v2[bitrate_index];
            break;      
        default:
            return false;
        }
        break;
    }
    if (bitrate == 0) return false;

    sample_rate = sample_rate_table[sample_rate_index];
    if (sample_rate == 0) return false;
    switch(mpeg_version)
    {
    case _MPEG_1:
        sample_rate *= 4;
        p_info.m_mpegversion = MPEG_1;
        break;
    case _MPEG_2:
        sample_rate *= 2;
        p_info.m_mpegversion = MPEG_2;
        break;
    case _MPEG_25:
        p_info.m_mpegversion = MPEG_25;
        break;
    }

    switch(channel_mode)
    {
    case 0:
    case 1:
    case 2:
        p_info.m_channels = 2;
        break;
    case 3:
        p_info.m_channels = 1;
        break;
    }

    p_info.m_channel_mode = channel_mode;

    p_info.m_sample_rate = sample_rate;


    p_info.m_bytes = ( bitrate /*kbps*/ * (1000/8) /* kbps-to-bytes*/ * p_info.m_duration /*samples-per-frame*/ ) / sample_rate + paddingdelta;

    if (p_info.m_layer == 1) p_info.m_bytes &= ~3;

    p_info.m_crc = protection == 0;

    return true;
}

unsigned mp3header::get_samples_per_frame()
{
    mp3_utils::TMPEGFrameInfo fr;
    if (!decode(fr)) return 0;
    return fr.m_duration;
}

bool mp3_utils::IsSameStream(TMPEGFrameInfo const & p_frame1,TMPEGFrameInfo const & p_frame2) {
    return 
        p_frame1.m_channel_mode == p_frame2.m_channel_mode && 
        p_frame1.m_sample_rate == p_frame2.m_sample_rate &&
        p_frame1.m_layer == p_frame2.m_layer &&
        p_frame1.m_mpegversion == p_frame2.m_mpegversion;
}



bool mp3_utils::ValidateFrameCRC(const t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
    if (frameSize < info.m_bytes) return false; //FAIL, incomplete data
    if (!info.m_crc) return true; //nothing to check, frame appears valid
    return ExtractFrameCRC(frameData, frameSize, info) == CalculateFrameCRC(frameData, frameSize, info);
}

static t_uint32 CRC_update(unsigned value, t_uint32 crc)
{
    enum { CRC16_POLYNOMIAL = 0x8005 };
    unsigned i;
    value <<= 8;
    for (i = 0; i < 8; i++) {
        value <<= 1;
        crc <<= 1;
        if (((crc ^ value) & 0x10000)) crc ^= CRC16_POLYNOMIAL;
    }
    return crc;
}


void mp3_utils::RecalculateFrameCRC(t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
    PFC_ASSERT( frameSize >= info.m_bytes && info.m_crc );

    const t_uint16 crc = CalculateFrameCRC(frameData, frameSize, info);
    frameData[4] = (t_uint8)(crc >> 8);
    frameData[5] = (t_uint8)(crc & 0xFF);
}

static t_uint16 grabFrameCRC(const t_uint8 * frameData, t_size sideInfoLen) {
    t_uint32 crc = 0xffff;
    crc = CRC_update(frameData[2], crc);
    crc = CRC_update(frameData[3], crc);
    for (t_size i = 6; i < sideInfoLen; i++) {
        crc = CRC_update(frameData[i], crc);
    }

    return (t_uint32) (crc & 0xFFFF);
}

t_uint16 mp3_utils::ExtractFrameCRC(const t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
    PFC_ASSERT( frameSize >= info.m_bytes && info.m_crc );

    return ((t_uint16)frameData[4] << 8) | (t_uint16)frameData[5];

}
t_uint16 mp3_utils::CalculateFrameCRC(const t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
    PFC_ASSERT( frameSize >= info.m_bytes && info.m_crc );

    t_size sideInfoLen = 0;
    if (info.m_mpegversion == MPEG_1)
        sideInfoLen = (info.m_channels == 1) ? 4 + 17 : 4 + 32;
    else
        sideInfoLen = (info.m_channels == 1) ? 4 + 9 : 4 + 17;

    //CRC
    sideInfoLen += 2;

    PFC_ASSERT( sideInfoLen  <= frameSize );

    return grabFrameCRC(frameData, sideInfoLen);
}


bool mp3_utils::ValidateFrameCRC(const t_uint8 * frameData, t_size frameSize) {
    if (frameSize < 4) return false; //FAIL, not a valid frame
    TMPEGFrameInfo info;
    if (!ParseMPEGFrameHeader(info, frameData)) return false; //FAIL, not a valid frame
    return ValidateFrameCRC(frameData, frameSize, info);
}