276 lines
7.3 KiB
C++
276 lines
7.3 KiB
C++
#include "stdafx.h"
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#include "mp3_utils.h"
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#include "bitreader_helper.h"
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using namespace bitreader_helper;
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static unsigned extract_header_bits(const t_uint8 p_header[4],unsigned p_base,unsigned p_bits)
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{
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PFC_ASSERT(p_base+p_bits<=32);
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return (unsigned) extract_bits(p_header,p_base,p_bits);
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}
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namespace {
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class header_parser
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{
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public:
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header_parser(const t_uint8 p_header[4]) : m_bitptr(0)
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{
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memcpy(m_header,p_header,4);
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}
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unsigned read(unsigned p_bits)
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{
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unsigned ret = extract_header_bits(m_header,m_bitptr,p_bits);
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m_bitptr += p_bits;
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return ret;
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}
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private:
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t_uint8 m_header[4];
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unsigned m_bitptr;
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};
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}
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typedef t_uint16 uint16;
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static const uint16 bitrate_table_l1v1[16] = { 0, 32, 64, 96,128,160,192,224,256,288,320,352,384,416,448, 0};
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static const uint16 bitrate_table_l2v1[16] = { 0, 32, 48, 56, 64, 80, 96,112,128,160,192,224,256,320,384, 0};
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static const uint16 bitrate_table_l3v1[16] = { 0, 32, 40, 48, 56, 64, 80, 96,112,128,160,192,224,256,320, 0};
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static const uint16 bitrate_table_l1v2[16] = { 0, 32, 48, 56, 64, 80, 96,112,128,144,160,176,192,224,256, 0};
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static const uint16 bitrate_table_l23v2[16] = { 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96,112,128,144,160, 0};
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static const uint16 sample_rate_table[] = {11025,12000,8000};
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unsigned mp3_utils::QueryMPEGFrameSize(const t_uint8 p_header[4])
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{
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TMPEGFrameInfo info;
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if (!ParseMPEGFrameHeader(info,p_header)) return 0;
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return info.m_bytes;
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}
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bool mp3_utils::ParseMPEGFrameHeader(TMPEGFrameInfo & p_info,const t_uint8 p_header[4])
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{
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enum {MPEG_LAYER_1 = 3, MPEG_LAYER_2 = 2, MPEG_LAYER_3 = 1};
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enum {_MPEG_1 = 3, _MPEG_2 = 2, _MPEG_25 = 0};
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header_parser parser(p_header);
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if (parser.read(11) != 0x7FF) return false;
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unsigned mpeg_version = parser.read(2);
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unsigned layer = parser.read(2);
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unsigned protection = parser.read(1);
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unsigned bitrate_index = parser.read(4);
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unsigned sample_rate_index = parser.read(2);
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if (sample_rate_index == 3) return false;//reserved
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unsigned paddingbit = parser.read(1);
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int paddingdelta = 0;
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parser.read(1);//private
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unsigned channel_mode = parser.read(2);
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unsigned channel_mode_ext = parser.read(2);//channel_mode_extension
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parser.read(1);//copyright
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parser.read(1);//original
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parser.read(2);//emphasis
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unsigned bitrate = 0,sample_rate = 0;
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switch(layer)
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{
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default:
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return false;
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case MPEG_LAYER_3:
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paddingdelta = paddingbit ? 1 : 0;
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p_info.m_layer = 3;
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switch(mpeg_version)
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{
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case _MPEG_1:
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p_info.m_duration = 1152;
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bitrate = bitrate_table_l3v1[bitrate_index];
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break;
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case _MPEG_2:
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case _MPEG_25:
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p_info.m_duration = 576;
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bitrate = bitrate_table_l23v2[bitrate_index];
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break;
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default:
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return false;
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}
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break;
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case MPEG_LAYER_2:
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paddingdelta = paddingbit ? 1 : 0;
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p_info.m_duration = 1152;
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p_info.m_layer = 2;
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switch(mpeg_version)
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{
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case _MPEG_1:
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bitrate = bitrate_table_l2v1[bitrate_index];
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break;
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case _MPEG_2:
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case _MPEG_25:
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bitrate = bitrate_table_l23v2[bitrate_index];
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break;
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default:
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return false;
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}
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break;
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case MPEG_LAYER_1:
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paddingdelta = paddingbit ? 4 : 0;
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p_info.m_duration = 384;
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p_info.m_layer = 1;
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switch(mpeg_version)
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{
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case _MPEG_1:
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bitrate = bitrate_table_l1v1[bitrate_index];
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break;
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case _MPEG_2:
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case _MPEG_25:
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bitrate = bitrate_table_l1v2[bitrate_index];
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break;
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default:
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return false;
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}
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break;
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}
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if (bitrate == 0) return false;
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sample_rate = sample_rate_table[sample_rate_index];
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if (sample_rate == 0) return false;
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switch(mpeg_version)
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{
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case _MPEG_1:
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sample_rate *= 4;
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p_info.m_mpegversion = MPEG_1;
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break;
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case _MPEG_2:
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sample_rate *= 2;
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p_info.m_mpegversion = MPEG_2;
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break;
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case _MPEG_25:
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p_info.m_mpegversion = MPEG_25;
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break;
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}
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switch(channel_mode)
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{
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case 0:
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case 1:
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case 2:
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p_info.m_channels = 2;
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break;
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case 3:
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p_info.m_channels = 1;
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break;
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}
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p_info.m_channel_mode = channel_mode;
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p_info.m_channel_mode_ext = channel_mode_ext;
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p_info.m_sample_rate = sample_rate;
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p_info.m_sample_rate_idx = sample_rate_index;
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p_info.m_bitrate = bitrate;
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p_info.m_bitrate_idx = bitrate_index;
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p_info.m_bytes = ( bitrate /*kbps*/ * (1000/8) /* kbps-to-bytes*/ * p_info.m_duration /*samples-per-frame*/ ) / sample_rate + paddingdelta;
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if (p_info.m_layer == 1) p_info.m_bytes &= ~3;
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p_info.m_crc = protection == 0;
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return true;
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}
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unsigned mp3header::get_samples_per_frame()
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{
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mp3_utils::TMPEGFrameInfo fr;
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if (!decode(fr)) return 0;
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return fr.m_duration;
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}
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bool mp3_utils::IsSameStream(TMPEGFrameInfo const & p_frame1,TMPEGFrameInfo const & p_frame2) {
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return
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// FFmpeg writes VBR headers with null channel mode...
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/* p_frame1.m_channel_mode == p_frame2.m_channel_mode && */
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p_frame1.m_sample_rate == p_frame2.m_sample_rate &&
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p_frame1.m_layer == p_frame2.m_layer &&
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p_frame1.m_mpegversion == p_frame2.m_mpegversion;
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}
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bool mp3_utils::ValidateFrameCRC(const t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
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if (frameSize < info.m_bytes) return false; //FAIL, incomplete data
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if (!info.m_crc) return true; //nothing to check, frame appears valid
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return ExtractFrameCRC(frameData, frameSize, info) == CalculateFrameCRC(frameData, frameSize, info);
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}
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static t_uint32 CRC_update(unsigned value, t_uint32 crc)
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{
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enum { CRC16_POLYNOMIAL = 0x8005 };
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unsigned i;
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value <<= 8;
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for (i = 0; i < 8; i++) {
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value <<= 1;
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crc <<= 1;
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if (((crc ^ value) & 0x10000)) crc ^= CRC16_POLYNOMIAL;
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}
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return crc;
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}
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void mp3_utils::RecalculateFrameCRC(t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
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PFC_ASSERT( frameSize >= info.m_bytes && info.m_crc );
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const t_uint16 crc = CalculateFrameCRC(frameData, frameSize, info);
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frameData[4] = (t_uint8)(crc >> 8);
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frameData[5] = (t_uint8)(crc & 0xFF);
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}
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static t_uint16 grabFrameCRC(const t_uint8 * frameData, t_size sideInfoLen) {
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t_uint32 crc = 0xffff;
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crc = CRC_update(frameData[2], crc);
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crc = CRC_update(frameData[3], crc);
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for (t_size i = 6; i < sideInfoLen; i++) {
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crc = CRC_update(frameData[i], crc);
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}
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return (t_uint32) (crc & 0xFFFF);
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}
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t_uint16 mp3_utils::ExtractFrameCRC(const t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
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PFC_ASSERT( frameSize >= info.m_bytes && info.m_crc );
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return ((t_uint16)frameData[4] << 8) | (t_uint16)frameData[5];
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}
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t_uint16 mp3_utils::CalculateFrameCRC(const t_uint8 * frameData, t_size frameSize, TMPEGFrameInfo const & info) {
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PFC_ASSERT( frameSize >= info.m_bytes && info.m_crc );
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t_size sideInfoLen = 0;
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if (info.m_mpegversion == MPEG_1)
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sideInfoLen = (info.m_channels == 1) ? 4 + 17 : 4 + 32;
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else
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sideInfoLen = (info.m_channels == 1) ? 4 + 9 : 4 + 17;
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//CRC
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sideInfoLen += 2;
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PFC_ASSERT( sideInfoLen <= frameSize );
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return grabFrameCRC(frameData, sideInfoLen);
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}
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bool mp3_utils::ValidateFrameCRC(const t_uint8 * frameData, t_size frameSize) {
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if (frameSize < 4) return false; //FAIL, not a valid frame
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TMPEGFrameInfo info;
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if (!ParseMPEGFrameHeader(info, frameData)) return false; //FAIL, not a valid frame
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return ValidateFrameCRC(frameData, frameSize, info);
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}
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bool mp3_utils::ParseMPEGFrameHeader(TMPEGFrameInfo & p_info, const void * bytes, size_t bytesAvail) {
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if (bytesAvail < 4) return false; //FAIL, not a valid frame
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return ParseMPEGFrameHeader(p_info, reinterpret_cast<const t_uint8*>(bytes));
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} |