在ios設備中進行錄音，錄音文件的格式為caf。但這種格式在很多設備中沒法播放。為了適應終端的播放功能，特將caf轉換為mp3格式文件來使用。
在錄制caf文件時，需要使用雙通道，否則在轉換為MP3格式時，聲音不對。caf錄制端的設置為：
NSMutableDictionary * recordSetting = [NSMutableDictionary dictionary];
[recordSetting setValue :[NSNumber numberWithInt:kAudioFormatLinearPCM] forKey:AVFormatIDKey];//
[recordSetting setValue:[NSNumber numberWithFloat:8000.0] forKey:AVSampleRateKey];//采樣率
[recordSetting setValue:[NSNumber numberWithInt: 2] forKey:AVNumberOfChannelsKey];//聲音通道，這里必須為雙通道
[recordSetting setValue:[NSNumber numberWithInt:AVAudioQualityLow] forKey:AVEncoderAudioQualityKey];//音頻質量
在轉換mp3端的代碼為:
NSString *cafFilePath = cafFilePathName; //caf文件路徑
NSString *mp3FilePath = mp3FilePathName;//存儲mp3文件的路徑
NSFileManager* fileManager=[NSFileManager defaultManager];
if([fileManager removeItemAtPath:mp3FilePath error:nil])
{
NSLog(@"刪除");
}
@try {
int read, write;
FILE *pcm = fopen([cafFilePath cStringUsingEncoding:1], "rb"); //source 被轉換的音頻文件位置
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 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_num_channels(lame,1);//設置1為單通道，默認為2雙通道
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 音質*/
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(@"執行完成");
}