使用第三方 lame ,Mp3音頻編碼器.

使用 AVAudioRecorder 進行音頻錄制之前,進行參數設置:

NSString *recordTemporaryPathString = [NSString stringWithFormat:@%@/temporary,self.audioTemporarySavePath];
//LinearPCM 是iOS的一種無損編碼格式,但是體積較為龐大
//錄音設置
NSMutableDictionary *recordSettings = [[NSMutableDictionary alloc] init];
//錄音格式 無法使用
[recordSettings setValue :[NSNumber numberWithInt:kAudioFormatLinearPCM] forKey: AVFormatIDKey];
//采樣率
[recordSettings setValue :[NSNumber numberWithFloat:11025.0] forKey: AVSampleRateKey];//44100.0
//通道數
[recordSettings setValue :[NSNumber numberWithInt:2] forKey: AVNumberOfChannelsKey];
//線性采樣位數
//[recordSettings setValue :[NSNumber numberWithInt:16] forKey: AVLinearPCMBitDepthKey];
//音頻質量,采樣質量
[recordSettings setValue:[NSNumber numberWithInt:AVAudioQualityMin] forKey:AVEncoderAudioQualityKey];

#include lame.h

- (void)audio_PCMtoMP3
{

NSString *mp3FileName = [self.audioFileSavePath lastPathComponent];
mp3FileName = [mp3FileName stringByAppendingString:@.mp3];
NSString *mp3FilePath = [self.audioTemporarySavePath stringByAppendingPathComponent:mp3FileName];

@try {
int read, write;

FILE *pcm = fopen([self.audioFileSavePath cStringUsingEncoding:1], rb); //source 被轉換的音頻文件位置
fseek(pcm, 4*1024, SEEK_CUR); //skip file header
FILE *mp3 = fopen([mp3FilePath cStringUsingEncoding:1], wb); //output 輸出生成的Mp3文件位置

const int PCM_SIZE = 8192;
const int MP3_SIZE = 8192;
short int pcm_buffer[PCM_SIZE*2];
unsigned char mp3_buffer[MP3_SIZE];

lame_t lame = lame_init();
lame_set_in_samplerate(lame, 11025.0);
lame_set_VBR(lame, vbr_default);
lame_init_params(lame);

do {
read = fread(pcm_buffer, 2*sizeof(short int), PCM_SIZE, pcm);
if (read == 0)
write = lame_encode_flush(lame, mp3_buffer, MP3_SIZE);
else
write = lame_encode_buffer_interleaved(lame, pcm_buffer, read, mp3_buffer, MP3_SIZE);

fwrite(mp3_buffer, write, 1, mp3);

} while (read != 0);

lame_close(lame);
fclose(mp3);
fclose(pcm);
}
@catch (NSException *exception) {
NSLog(@%@,[exception description]);
}
@finally {
self.audioFileSavePath = mp3FilePath;
NSLog(@MP3生成成功: %@,self.audioFileSavePath);
}

}