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#include "OFL.h"
#include "foundation/error.h"
static void crcofl(unsigned short crcPoly, unsigned short crcMask, unsigned long *crc, unsigned char byte)
{
int i;
for (i=0; i<8; i++)
{
unsigned short flag = (*crc) & crcMask ? 1:0;
flag ^= (byte & 0x80 ? 1 : 0);
(*crc)<<=1;
byte <<= 1;
if(flag)
(*crc) ^= crcPoly;
}
}
int OFL::GetGaps(size_t *pregap, size_t *postgap)
{
/* TODO: verify the postgap calculation */
if (codec_delay >= 529)
{
*pregap = codec_delay;
size_t endcut;
endcut = samples_per_frame - ((total_length + codec_delay) % samples_per_frame); // how many 0 samples had to be added?
*postgap = endcut;
return NErr_Success;
}
return NErr_Empty;
}
double OFL::GetLengthSeconds() const
{
return (double)GetSamples() / (double)sample_rate;
}
uint64_t OFL::GetSamples() const
{
return total_length;
}
uint32_t OFL::GetFrames() const
{
uint64_t real_samples = (total_length+codec_delay)*samples_per_frame;
return (uint32_t) (real_samples/samples_per_frame);
}
int OFL::Read(const MPEGFrame &header, const uint8_t *buffer, size_t buffer_len)
{
if (header.layer != MPEGFrame::Layer3)
return NErr_False;
sample_rate = header.GetSampleRate();
samples_per_frame = header.GetSamplesPerFrame();
if (header.channelMode == MPEGFrame::Mono)
{
if (header.mpegVersion == MPEGFrame::MPEG1)
{
// 0-9 : main_data_end
int16_t main_data_end = (buffer[0] << 1) | (buffer[1] >> 7);
// read the 2 part2_3_lengths out so we know how big the main data section is
uint16_t part2_3_length = ((buffer[2] & 0x3F) << 6) | (buffer[3]>>2); // bits 18-30
part2_3_length += ((buffer[9] & 0x7) << 9) | (buffer[10] << 1) | (buffer[11] >> 7) ; // bits 77-89
size_t offset = 17 + (part2_3_length+7)/8;
if (offset+9 < buffer_len && buffer[offset] == 0xb4)
{
unsigned long crc=255;
for (int i=0;i<9;i++)
crcofl(0x0045, 0x0080, &crc, buffer[offset+i]);
if ((crc & 0xFF) == buffer[offset+9])
{
total_length = (buffer[offset+3] << 24) | (buffer[offset+4] << 16) | (buffer[offset+5] << 8) | (buffer[offset+6]);
codec_delay = (buffer[offset+1] << 8) | (buffer[offset+2]);
additional_delay= (buffer[offset+7] << 8) | (buffer[offset+8]);
return NErr_Success;
}
}
}
else
{ // MPEG2 and 2.5
// 0-8 : main_data_end
uint16_t main_data_end = buffer[0];
// read the 2 part2_3_lengths out so we know how big the main data section is
uint16_t part2_3_length = ((buffer[1] & 0x7F) << 5) | (buffer[2]>>3); // bits 9-21
size_t offset = 9 + (part2_3_length+7)/8;
if (offset+9 < buffer_len && buffer[offset] == 0xb4)
{
unsigned long crc=255;
for (int i=0;i<9;i++)
crcofl(0x0045, 0x0080, &crc, buffer[offset+i]);
if ((crc & 0xFF) == buffer[offset+9])
{
total_length = (buffer[offset+3] << 24) | (buffer[offset+4] << 16) | (buffer[offset+5] << 8) | (buffer[offset+6]);
codec_delay = (buffer[offset+1] << 8) | (buffer[offset+2]);
additional_delay= (buffer[offset+7] << 8) | (buffer[offset+8]);
return NErr_Success;
}
}
}
}
else
{
if (header.mpegVersion == MPEGFrame::MPEG1)
{
// 0-9 : main_data_end
uint16_t main_data_end = (buffer[0] << 1) | (buffer[1] >> 7);
// read the 4 part2_3_lengths out so we know how big the main data section is
uint16_t part2_3_length = ((buffer[2] & 0xF) << 8) | buffer[3]; // bits 20-32
part2_3_length += ((buffer[9] & 0x1) << 11) | (buffer[10] << 3) | (buffer[11] >> 5) ; // bits 79-91
part2_3_length += ((buffer[17] & 0x3F) << 6) | (buffer[18] >> 2); // bits 138-150
part2_3_length += ((buffer[24] & 0x7) << 9) | (buffer[25] << 1) | (buffer[26] >> 7); // bits 197-209
size_t offset = 32 + (part2_3_length+7)/8;
if (offset+9 < buffer_len && buffer[offset] == 0xb4)
{
unsigned long crc=255;
for (int i=0;i<9;i++)
crcofl(0x0045, 0x0080, &crc, buffer[offset+i]);
if ((crc & 0xFF) == buffer[offset+9])
{
total_length = (buffer[offset+3] << 24) | (buffer[offset+4] << 16) | (buffer[offset+5] << 8) | (buffer[offset+6]);
codec_delay = (buffer[offset+1] << 8) | (buffer[offset+2]);
additional_delay= (buffer[offset+7] << 8) | (buffer[offset+8]);
return NErr_Success;
}
}
}
else
{ // MPEG2 and 2.5
// 0-8 : main_data_end
uint16_t main_data_end = buffer[0];
// read the 4 part2_3_lengths out so we know how big the main data section is
uint16_t part2_3_length = ((buffer[1] & 0x3F) << 6) | (buffer[2] >> 2); // bits 10-22
part2_3_length += ((buffer[8] & 0x7) << 9) | (buffer[9] << 1) | (buffer[10] >> 7) ; // bits 69-81
size_t offset = 17 + (part2_3_length+7)/8;
if (offset+9 < buffer_len && buffer[offset] == 0xb4)
{
unsigned long crc=255;
for (int i=0;i<9;i++)
crcofl(0x0045, 0x0080, &crc, buffer[offset+i]);
if ((crc & 0xFF) == buffer[offset+9])
{
total_length = (buffer[offset+3] << 24) | (buffer[offset+4] << 16) | (buffer[offset+5] << 8) | (buffer[offset+6]);
codec_delay = (buffer[offset+1] << 8) | (buffer[offset+2]);
additional_delay= (buffer[offset+7] << 8) | (buffer[offset+8]);
return NErr_Success;
}
}
}
}
return NErr_False;
}
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