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cog/Plugins/MAD/MADDecoder.m

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//
// MADFile.m
// Cog
//
// Created by Vincent Spader on 6/17/06.
// Copyright 2006 Vincent Spader. All rights reserved.
//
#import "MADDecoder.h"
#import "HTTPSource.h"
#import "Logging.h"
#import "id3tag.h"
#import <Accelerate/Accelerate.h>
#import "CVbriHeader.h"
@implementation MADDecoder
#define LAME_HEADER_SIZE ((8 * 5) + 4 + 4 + 8 + 32 + 16 + 16 + 4 + 4 + 8 + 12 + 12 + 8 + 8 + 2 + 3 + 11 + 32 + 32 + 32)
// From vbrheadersdk:
// ========================================
// A Xing header may be present in the ancillary
// data field of the first frame of an mp3 bitstream
// The Xing header (optionally) contains
// frames total number of audio frames in the bitstream
// bytes total number of bytes in the bitstream
// toc table of contents
// toc (table of contents) gives seek points
// for random access
// the ith entry determines the seek point for
// i-percent duration
// seek point in bytes = (toc[i]/256.0) * total_bitstream_bytes
// e.g. half duration seek point = (toc[50]/256.0) * total_bitstream_bytes
#define FRAMES_FLAG 0x0001
#define BYTES_FLAG 0x0002
#define TOC_FLAG 0x0004
#define VBR_SCALE_FLAG 0x0008
// Scan file quickly
- (void)bufferRefill:(struct mad_stream *)stream {
long bytesToRead, bytesRemaining;
if(NULL == stream->buffer || MAD_ERROR_BUFLEN == stream->error) {
if(stream->next_frame) {
bytesRemaining = stream->bufend - stream->next_frame;
memmove(_inputBuffer, stream->next_frame, bytesRemaining);
bytesToRead = INPUT_BUFFER_SIZE - bytesRemaining;
} else {
bytesToRead = INPUT_BUFFER_SIZE;
bytesRemaining = 0;
}
// Read raw bytes from the MP3 file
long bytesRead = [_source read:_inputBuffer + bytesRemaining amount:bytesToRead];
if(bytesRead == 0) {
memset(_inputBuffer + bytesRemaining + bytesRead, 0, MAD_BUFFER_GUARD);
bytesRead += MAD_BUFFER_GUARD;
inputEOF = YES;
}
mad_stream_buffer(stream, _inputBuffer, bytesRead + bytesRemaining);
stream->error = MAD_ERROR_NONE;
}
}
- (BOOL)scanFile {
struct mad_stream stream;
struct mad_frame frame;
long framesDecoded = 0;
int samplesPerMPEGFrame = 0;
int id3_length = 0;
mad_stream_init(&stream);
mad_frame_init(&frame);
[_source seek:0 whence:SEEK_END];
_fileSize = [_source tell];
[_source seek:0 whence:SEEK_SET];
for(;;) {
[self bufferRefill:&stream];
if(mad_frame_decode(&frame, &stream) == -1) {
if(MAD_RECOVERABLE(stream.error)) {
// Prevent ID3 tags from reporting recoverable frame errors
const uint8_t *buffer = stream.this_frame;
unsigned long buflen = stream.bufend - stream.this_frame;
if(10 <= buflen && 0x49 == buffer[0] && 0x44 == buffer[1] && 0x33 == buffer[2]) {
id3_length = (((buffer[6] & 0x7F) << (3 * 7)) | ((buffer[7] & 0x7F) << (2 * 7)) |
((buffer[8] & 0x7F) << (1 * 7)) | ((buffer[9] & 0x7F) << (0 * 7)));
_foundID3v2 = YES;
// Add 10 bytes for ID3 header
id3_length += 10;
void *tagBuffer = malloc(id3_length);
if(!tagBuffer) return NO;
memcpy(tagBuffer, &buffer[0], MIN(buflen, id3_length));
long bufleft = id3_length - buflen;
long tagRead = MIN(buflen, id3_length);
while(bufleft > 0) {
stream.error = MAD_ERROR_BUFLEN;
stream.next_frame = NULL;
[self bufferRefill:&stream];
buffer = stream.this_frame;
buflen = stream.bufend - stream.this_frame;
memcpy(tagBuffer + tagRead, buffer, MIN(buflen, bufleft));
tagRead += MIN(buflen, bufleft);
bufleft -= buflen;
}
if(bufleft < 0) {
mad_stream_skip(&stream, buflen + bufleft);
}
struct id3_tag *tag = id3_tag_parse(tagBuffer, id3_length);
if(tag) {
for(size_t i = 0; i < tag->nframes; ++i) {
struct id3_frame *frame = tag->frames[i];
if(!strcmp(frame->id, "COMM")) {
union id3_field *field;
const id3_ucs4_t *description;
const id3_ucs4_t *value;
field = id3_frame_field(frame, 2);
description = id3_field_getstring(field);
field = id3_frame_field(frame, 3);
value = id3_field_getfullstring(field);
if(description && value) {
id3_utf8_t *description8 = id3_ucs4_utf8duplicate(description);
if(!strcmp((const char *)description8, "iTunSMPB")) {
id3_utf8_t *value8 = id3_ucs4_utf8duplicate(value);
uint32_t zero, start_pad, end_pad;
uint64_t last_eight_frames_offset;
int64_t temp_duration;
if(sscanf((const char *)value8, "%" PRIx32 " %" PRIx32 " %" PRIx32 " %" PRIx64 " %" PRIx32 " %" PRIx64, &zero, &start_pad, &end_pad, &temp_duration, &zero, &last_eight_frames_offset) == 6 &&
temp_duration >= 0 &&
start_pad <= (576 * 2 * 32) &&
end_pad <= (576 * 2 * 64) &&
(_fileSize && (last_eight_frames_offset < (_fileSize - id3_length)))) {
if(end_pad >= 528 + 1) {
_startPadding = start_pad + 528 + 1;
_endPadding = end_pad - (528 + 1);
// iTunes encodes the original length of the file here
totalFrames = temp_duration + _startPadding + _endPadding;
_foundiTunSMPB = YES;
}
}
free(value8);
}
free(description8);
}
}
}
id3_tag_delete(tag);
}
free(tagBuffer);
} else if(stream.error == MAD_ERROR_BADDATAPTR) {
goto framedecoded;
}
continue;
} else if(stream.error == MAD_ERROR_BUFLEN && inputEOF) {
break;
} else if(stream.error == MAD_ERROR_BUFLEN) {
continue;
} else {
// DLog(@"Unrecoverable error: %s", mad_stream_errorstr(&stream));
break;
}
}
framedecoded:
framesDecoded++;
if(framesDecoded == 1) {
sampleRate = frame.header.samplerate;
channels = MAD_NCHANNELS(&frame.header);
if(MAD_FLAG_LSF_EXT & frame.header.flags || MAD_FLAG_MPEG_2_5_EXT & frame.header.flags) {
switch(frame.header.layer) {
case MAD_LAYER_I:
samplesPerMPEGFrame = 384;
layer = 1;
break;
case MAD_LAYER_II:
samplesPerMPEGFrame = 1152;
layer = 2;
break;
case MAD_LAYER_III:
samplesPerMPEGFrame = 576;
layer = 3;
break;
}
} else {
switch(frame.header.layer) {
case MAD_LAYER_I:
samplesPerMPEGFrame = 384;
layer = 1;
break;
case MAD_LAYER_II:
samplesPerMPEGFrame = 1152;
layer = 2;
break;
case MAD_LAYER_III:
samplesPerMPEGFrame = 1152;
layer = 3;
break;
}
}
if(layer != 3) continue;
const size_t ancillaryBitsRemaining = (stream.next_frame - stream.this_frame) * 8;
static const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
const int64_t xing_offset = xing_offtbl[!!(MAD_FLAG_LSF_EXT & frame.header.flags || MAD_FLAG_MPEG_2_5_EXT & frame.header.flags)][channels == 1] + 4; // Plus MPEG header
size_t ancBitsRemainingXing = ancillaryBitsRemaining - xing_offset * 8;
if(ancBitsRemainingXing >= 32) {
const uint8_t *ptr = stream.this_frame + xing_offset;
struct mad_bitptr bitptr;
mad_bit_init(&bitptr, ptr);
uint32_t magic = (uint32_t)mad_bit_read(&bitptr, 32);
ancBitsRemainingXing -= 32;
if('Xing' == magic || 'Info' == magic) {
unsigned i;
uint32_t flags = 0, frames = 0, bytes = 0, vbrScale = 0;
if(32 > ancBitsRemainingXing)
continue;
flags = (uint32_t)mad_bit_read(&bitptr, 32);
ancBitsRemainingXing -= 32;
// 4 byte value containing total frames
if(FRAMES_FLAG & flags) {
if(32 > ancBitsRemainingXing)
continue;
frames = (uint32_t)mad_bit_read(&bitptr, 32);
ancBitsRemainingXing -= 32;
// Determine number of samples, discounting encoder delay and padding
// Our concept of a frame is the same as CoreAudio's- one sample across all channels
totalFrames = frames * samplesPerMPEGFrame;
// DLog(@"TOTAL READ FROM XING");
}
// 4 byte value containing total bytes
if(BYTES_FLAG & flags) {
if(32 > ancBitsRemainingXing)
continue;
bytes = (uint32_t)mad_bit_read(&bitptr, 32);
ancBitsRemainingXing -= 32;
}
// 100 bytes containing TOC information
if(TOC_FLAG & flags) {
if(8 * 100 > ancBitsRemainingXing)
continue;
for(i = 0; i < 100; ++i)
/*_xingTOC[i] = */ mad_bit_read(&bitptr, 8);
ancBitsRemainingXing -= (8 * 100);
}
// 4 byte value indicating encoded vbr scale
if(VBR_SCALE_FLAG & flags) {
if(32 > ancBitsRemainingXing)
continue;
vbrScale = (uint32_t)mad_bit_read(&bitptr, 32);
ancBitsRemainingXing -= 32;
}
framesDecoded = frames;
_foundXingHeader = YES;
// Loook for the LAME header next
// http://gabriel.mp3-tech.org/mp3infotag.html
if(32 > ancBitsRemainingXing)
continue;
magic = (uint32_t)mad_bit_read(&bitptr, 32);
ancBitsRemainingXing -= 32;
if('LAME' == magic || 'Lavf' == magic || 'Lavc' == magic) {
if(LAME_HEADER_SIZE > ancBitsRemainingXing)
continue;
/*unsigned char versionString [5 + 1];
memset(versionString, 0, 6);*/
for(i = 0; i < 5; ++i)
/*versionString[i] =*/mad_bit_read(&bitptr, 8);
/*uint8_t infoTagRevision =*/mad_bit_read(&bitptr, 4);
/*uint8_t vbrMethod =*/mad_bit_read(&bitptr, 4);
/*uint8_t lowpassFilterValue =*/mad_bit_read(&bitptr, 8);
/*float peakSignalAmplitude =*/mad_bit_read(&bitptr, 32);
/*uint16_t radioReplayGain =*/mad_bit_read(&bitptr, 16);
/*uint16_t audiophileReplayGain =*/mad_bit_read(&bitptr, 16);
/*uint8_t encodingFlags =*/mad_bit_read(&bitptr, 4);
/*uint8_t athType =*/mad_bit_read(&bitptr, 4);
/*uint8_t lameBitrate =*/mad_bit_read(&bitptr, 8);
_startPadding = mad_bit_read(&bitptr, 12);
_endPadding = mad_bit_read(&bitptr, 12);
_startPadding += 528 + 1; // MDCT/filterbank delay
_endPadding -= 528 + 1;
/*uint8_t misc =*/mad_bit_read(&bitptr, 8);
/*uint8_t mp3Gain =*/mad_bit_read(&bitptr, 8);
/*DLog(@"Gain: %i", mp3Gain);*/
/*uint8_t unused =*/mad_bit_read(&bitptr, 2);
/*uint8_t surroundInfo =*/mad_bit_read(&bitptr, 3);
/*uint16_t presetInfo =*/mad_bit_read(&bitptr, 11);
/*uint32_t musicGain =*/mad_bit_read(&bitptr, 32);
/*uint32_t musicCRC =*/mad_bit_read(&bitptr, 32);
/*uint32_t tagCRC =*/mad_bit_read(&bitptr, 32);
ancBitsRemainingXing -= LAME_HEADER_SIZE;
_foundLAMEHeader = YES;
break;
}
}
}
const size_t vbri_offset = 4 + 32;
size_t ancBitsRemainingVBRI = ancillaryBitsRemaining - vbri_offset * 8;
if(ancBitsRemainingVBRI >= 32) {
const uint8_t *ptr = stream.this_frame + vbri_offset;
struct mad_bitptr bitptr;
mad_bit_init(&bitptr, ptr);
uint32_t magic = (uint32_t)mad_bit_read(&bitptr, 32);
ancBitsRemainingVBRI -= 32;
if('VBRI' == magic) {
struct VbriHeader *vbri_header = 0;
if(readVbriHeader(&vbri_header, mad_bit_nextbyte(&bitptr), ancBitsRemainingVBRI / 8) == 0) {
uint32_t frames = VbriTotalFrames(vbri_header);
totalFrames = frames * samplesPerMPEGFrame;
_startPadding = 0;
_endPadding = 0;
_foundVBRIHeader = YES;
}
if(vbri_header) {
freeVbriHeader(vbri_header);
}
break;
}
}
} else if(_foundXingHeader || _foundiTunSMPB || _foundVBRIHeader) {
break;
} else if(framesDecoded > 1) {
break;
}
}
if(!_foundiTunSMPB && !_foundXingHeader && !_foundVBRIHeader) {
// Now do CBR estimation instead of full file scanning
size_t frameCount = (_fileSize - id3_length) / (stream.next_frame - stream.this_frame);
mad_timer_t duration = frame.header.duration;
mad_timer_multiply(&duration, frameCount);
totalFrames = mad_timer_count(duration, sampleRate);
}
bitrate = ((double)((_fileSize - id3_length) * 8) / 1000.0) * (sampleRate / (double)totalFrames);
mad_frame_finish(&frame);
mad_stream_finish(&stream);
[_source seek:0 whence:SEEK_SET];
inputEOF = NO;
DLog(@"Mad properties: %@", [self properties]);
return YES;
}
- (BOOL)open:(id<CogSource>)source {
_source = source;
/* First the structures used by libmad must be initialized. */
mad_stream_init(&_stream);
mad_frame_init(&_frame);
mad_synth_init(&_synth);
_firstFrame = YES;
_outputFrames = 0;
_startPadding = 0;
_endPadding = 0;
// DLog(@"OPEN: %i", _firstFrame);
inputEOF = NO;
genre = @"";
album = @"";
artist = @"";
title = @"";
if(![_source seekable]) {
// Decode the first frame to get the channels, samplerate, etc.
int r;
do {
r = [self decodeMPEGFrame];
DLog(@"Decoding first frame: %i", r);
} while(r == 0);
return (r == -1 ? NO : YES);
}
framesToSkip = 0;
BOOL ret = [self scanFile];
if(_foundLAMEHeader || _foundiTunSMPB) {
framesToSkip = _startPadding;
}
return ret;
}
- (void)writeOutput {
unsigned long startingSample = 0;
unsigned long sampleCount = _synth.pcm.length;
// DLog(@"Position: %li/%li", _framesDecoded, totalFrames);
// DLog(@"<%i, %i>", _startPadding, _endPadding);
if(framesToSkip > 0) {
startingSample = framesToSkip;
}
// DLog(@"Counts: %i, %i", startingSample, sampleCount);
if(_foundLAMEHeader || _foundiTunSMPB) {
// Past the end of the file.
if(totalFrames - _endPadding <= _framesDecoded) {
// DLog(@"End of file. Not writing.");
return;
}
// Clip this for the following calculation, so this doesn't underflow
// when seeking and skipping a lot of samples
unsigned long startingSampleClipped = MIN(startingSample, sampleCount);
// We are at the end of the file and need to read the last few frames
if(_framesDecoded + (sampleCount - startingSampleClipped) > totalFrames - _endPadding) {
// DLog(@"End of file. %li", totalFrames - _endPadding - _framesDecoded);
sampleCount = totalFrames - _endPadding - _framesDecoded + startingSample;
}
}
// We haven't even gotten to the start yet
if(startingSample >= sampleCount) {
// DLog(@"Skipping entire sample");
_framesDecoded += sampleCount;
framesToSkip -= sampleCount;
return;
}
framesToSkip = 0;
// DLog(@"Revised: %i, %i", startingSample, sampleCount);
_framesDecoded += sampleCount;
if(_outputFrames > 0) {
DLog(@"LOSING FRAMES!");
}
_outputFrames = (sampleCount - startingSample);
if(_currentOutputFrames < _outputFrames) {
_outputBuffer = (float *)realloc(_outputBuffer, _outputFrames * channels * sizeof(float));
_currentOutputFrames = _outputFrames;
}
int ch;
// samples [0 ... n]
for(ch = 0; ch < channels; ch++) {
vDSP_vflt32(&_synth.pcm.samples[ch][startingSample], 1, &_outputBuffer[ch], channels, _outputFrames);
}
float scale = (float)MAD_F_ONE;
vDSP_vsdiv(&_outputBuffer[0], 1, &scale, &_outputBuffer[0], 1, _outputFrames * channels);
// Output to a file
// FILE *f = fopen("data.raw", "a");
// fwrite(_outputBuffer, channels * 2, _outputFrames, f);
// fclose(f);
}
- (int)decodeMPEGFrame {
if(_stream.buffer == NULL || _stream.error == MAD_ERROR_BUFLEN) {
int inputToRead;
int inputRemaining;
if(_stream.next_frame != NULL) {
inputRemaining = (int)(_stream.bufend - _stream.next_frame);
memmove(_inputBuffer, _stream.next_frame, inputRemaining);
inputToRead = INPUT_BUFFER_SIZE - inputRemaining;
} else {
inputToRead = INPUT_BUFFER_SIZE;
inputRemaining = 0;
}
long inputRead = [_source read:_inputBuffer + inputRemaining amount:INPUT_BUFFER_SIZE - inputRemaining];
if(inputRead == 0) {
memset(_inputBuffer + inputRemaining + inputRead, 0, MAD_BUFFER_GUARD);
inputRead += MAD_BUFFER_GUARD;
inputEOF = YES;
}
mad_stream_buffer(&_stream, _inputBuffer, inputRead + inputRemaining);
_stream.error = MAD_ERROR_NONE;
// DLog(@"Read stream.");
}
BOOL skippingBadFrame = NO;
if(mad_frame_decode(&_frame, &_stream) == -1) {
if(_stream.error == MAD_ERROR_BADDATAPTR) {
skippingBadFrame = YES;
} else if(MAD_RECOVERABLE(_stream.error)) {
const uint8_t *buffer = _stream.this_frame;
unsigned long buflen = _stream.bufend - _stream.this_frame;
uint32_t id3_length = 0;
// No longer need ID3Tag framework
if(10 <= buflen && 0x49 == buffer[0] && 0x44 == buffer[1] && 0x33 == buffer[2]) {
id3_length = (((buffer[6] & 0x7F) << (3 * 7)) | ((buffer[7] & 0x7F) << (2 * 7)) |
((buffer[8] & 0x7F) << (1 * 7)) | ((buffer[9] & 0x7F) << (0 * 7)));
// Add 10 bytes for ID3 header
id3_length += 10;
mad_stream_skip(&_stream, id3_length);
}
DLog(@"recoverable error");
return 0;
} else if(MAD_ERROR_BUFLEN == _stream.error && inputEOF) {
DLog(@"EOF");
return -1;
} else if(MAD_ERROR_BUFLEN == _stream.error) {
// DLog(@"Bufferlen");
return 0;
} else {
// DLog(@"Unrecoverable stream error: %s", mad_stream_errorstr(&_stream));
return -1;
}
}
if(!_firstFrame || !(_foundXingHeader && _foundVBRIHeader)) {
signed long frameDuration = mad_timer_count(_frame.header.duration, sampleRate);
if((framesToSkip - 1152 * 4) >= frameDuration) {
framesToSkip -= frameDuration;
_framesDecoded += frameDuration;
return 0;
}
}
// DLog(@"Decoded buffer.");
if(!skippingBadFrame) {
mad_synth_frame(&_synth, &_frame);
}
// DLog(@"first frame: %i", _firstFrame);
if(_firstFrame) {
_firstFrame = NO;
if(![_source seekable]) {
sampleRate = _frame.header.samplerate;
channels = MAD_NCHANNELS(&_frame.header);
switch(_frame.header.layer) {
case MAD_LAYER_I:
layer = 1;
break;
case MAD_LAYER_II:
layer = 2;
break;
case MAD_LAYER_III:
layer = 3;
break;
default:
break;
}
[self willChangeValueForKey:@"properties"];
[self didChangeValueForKey:@"properties"];
}
// DLog(@"FIRST FRAME!!! %i %i", _foundXingHeader, _foundLAMEHeader);
if(_foundXingHeader || _foundVBRIHeader) {
// DLog(@"Skipping xing header.");
return 0;
}
} else if(skippingBadFrame) {
return 0;
}
return 1;
}
- (BOOL)syncFormat:(BOOL)updateNow {
float _sampleRate = _frame.header.samplerate;
int _channels = MAD_NCHANNELS(&_frame.header);
int _layer = 3;
switch(_frame.header.layer) {
case MAD_LAYER_I:
_layer = 1;
break;
case MAD_LAYER_II:
_layer = 2;
break;
case MAD_LAYER_III:
_layer = 3;
break;
default:
break;
}
BOOL changed = (_sampleRate != sampleRate ||
_channels != channels ||
_layer != layer);
if(changed && updateNow) {
sampleRate = _sampleRate;
channels = _channels;
layer = _layer;
[self willChangeValueForKey:@"properties"];
[self didChangeValueForKey:@"properties"];
}
return changed;
}
- (int)readAudio:(void *)buffer frames:(UInt32)frames {
int framesRead = 0;
if(!_firstFrame)
[self syncFormat:YES];
for(;;) {
long framesRemaining = frames - framesRead;
long framesToCopy = (_outputFrames > framesRemaining ? framesRemaining : _outputFrames);
if(framesToCopy) {
memcpy(buffer + (framesRead * channels * sizeof(float)), _outputBuffer, framesToCopy * channels * sizeof(float));
framesRead += framesToCopy;
if(framesToCopy != _outputFrames) {
memmove(_outputBuffer, _outputBuffer + (framesToCopy * channels), (_outputFrames - framesToCopy) * channels * sizeof(float));
}
_outputFrames -= framesToCopy;
}
if(framesRead == frames)
break;
int r = [self decodeMPEGFrame];
// DLog(@"Decoding frame: %i", r);
if(r == 0) // Recoverable error.
continue;
else if(r == -1) // Unrecoverable error
break;
[self writeOutput];
// DLog(@"Wrote output");
if([self syncFormat:NO]) {
if(framesRead)
break;
else
[self syncFormat:YES];
}
}
[self updateMetadata];
// DLog(@"Read: %i/%i", bytesRead, size);
return framesRead;
}
- (void)close {
if(_source) {
[_source close];
_source = nil;
}
if(_outputBuffer) {
free(_outputBuffer);
_outputBuffer = NULL;
_currentOutputFrames = 0;
}
mad_synth_finish(&_synth);
mad_frame_finish(&_frame);
mad_stream_finish(&_stream);
}
- (long)seek:(long)frame {
if(frame == _framesDecoded) {
return frame;
}
if(frame > totalFrames)
frame = totalFrames;
framesToSkip = 0;
if(_foundLAMEHeader || _foundiTunSMPB) {
if(_framesDecoded < _startPadding) {
framesToSkip = _startPadding;
}
}
if(frame < _framesDecoded) {
_framesDecoded = 0;
_firstFrame = YES;
if(_foundLAMEHeader || _foundiTunSMPB)
framesToSkip = _startPadding;
[_source seek:0 whence:SEEK_SET];
mad_stream_buffer(&_stream, NULL, 0);
}
framesToSkip += frame - _framesDecoded;
return frame;
}
- (void)updateMetadata {
NSString *_artist = artist;
NSString *_album = album;
NSString *_title = title;
NSString *_genre = genre;
Class sourceClass = [_source class];
if([sourceClass isEqual:NSClassFromString(@"HTTPSource")]) {
HTTPSource *httpSource = (HTTPSource *)_source;
if([httpSource hasMetadata]) {
NSDictionary *metadata = [httpSource metadata];
_genre = [metadata valueForKey:@"genre"];
_album = [metadata valueForKey:@"album"];
_artist = [metadata valueForKey:@"artist"];
_title = [metadata valueForKey:@"title"];
}
}
if(![_artist isEqual:artist] ||
![_album isEqual:album] ||
![_title isEqual:title] ||
![_genre isEqual:genre]) {
artist = _artist;
album = _album;
title = _title;
genre = _genre;
if(![_source seekable]) {
[self willChangeValueForKey:@"metadata"];
[self didChangeValueForKey:@"metadata"];
}
}
}
- (NSDictionary *)properties {
if(layer < 1 || layer > 3) return nil;
const NSString *layers[3] = { @"MP1", @"MP2", @"MP3" };
return @{ @"channels": @(channels),
@"bitsPerSample": @(32),
@"sampleRate": @(sampleRate),
@"floatingPoint": @(YES),
@"bitrate": @(bitrate),
@"totalFrames": @(totalFrames - (_startPadding + _endPadding)),
@"seekable": @([_source seekable]),
@"codec": layers[layer - 1],
@"endian": @"host",
@"encoding": @"lossy" };
}
- (NSDictionary *)metadata {
return @{ @"artist": artist, @"album": album, @"title": title, @"genre": genre };
}
+ (NSArray *)fileTypes {
return @[@"mp3", @"m2a", @"mpa"];
}
+ (NSArray *)mimeTypes {
return @[@"audio/mpeg", @"audio/x-mp3"];
}
+ (NSArray *)fileTypeAssociations {
return @[@[@"MPEG Audio File", @"mp3.icns", @"mp3", @"m2a", @"mpa"]];
}
+ (float)priority {
return 2.0;
}
@end
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