在ios设备中进行录音，录音文件的格式为caf。但这种格式在很多设备中没法播放。为了适应终端的播放功能，特将caf转换为mp3格式文件来使用。
在录制caf文件时，需要使用双通道，否则在转换为MP3格式时，声音不对。caf录制端的设置为：
NSMutableDictionary * recordSetting = [NSMutableDictionary dictionary];
[recordSetting setValue :[NSNumber numberWithInt:kAudioFormatLinearPCM] forKey:AVFormatIDKey];//
[recordSetting setValue:[NSNumber numberWithFloat:8000.0] forKey:AVSampleRateKey];//采样率
[recordSetting setValue:[NSNumber numberWithInt: 2] forKey:AVNumberOfChannelsKey];//声音通道，这里必须为双通道
[recordSetting setValue:[NSNumber numberWithInt:AVAudioQualityLow] forKey:AVEncoderAudioQualityKey];//音频质量
在转换mp3端的代码为:
NSString *cafFilePath = cafFilePathName; //caf文件路径
NSString *mp3FilePath = mp3FilePathName;//存储mp3文件的路径
NSFileManager* fileManager=[NSFileManager defaultManager];
if([fileManager removeItemAtPath:mp3FilePath error:nil])
{
NSLog(@"删除");
}
@try {
int read, write;
FILE *pcm = fopen([cafFilePath cStringUsingEncoding:1], "rb"); //source 被转换的音频文件位置
if(pcm == NULL)
{
NSLog(@"file not found");
}
else
{
fseek(pcm, 4*1024, SEEK_CUR); //skip file header
FILE *mp3 = fopen([mp3FilePath cStringUsingEncoding:1], "wb"); //output 输出生成的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_num_channels(lame,1);//设置1为单通道，默认为2双通道
lame_set_in_samplerate(lame, 8000.0);//11025.0
//lame_set_VBR(lame, vbr_default);
lame_set_brate(lame,8);
lame_set_mode(lame,3);
lame_set_quality(lame,2); /* 2=high 5 = medium 7=low 音质*/
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);
return YES;
}
return NO;
}
@catch (NSException *exception) {
NSLog(@"%@",[exception description]);
return NO;
}
@finally {
NSLog(@"执行完成");
}