[iOS-GQiang]转换音频文件mp3

使用AVAudioRecorder录制下来的音频文件很大，所以下面我们用lame框架来将录制下来的音频文件转换成mp3格式的文件并缩小。

将几Mb的文件压缩成几kb的文件，这样就能方便开发者们使用了。

lame框架到Github上下载即可。

#pragma mark - 转换mp3
- (void)audio_PCMtoMP3
{
NSString *cafFilePath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/downloadFile.caf"];

NSString *mp3FilePath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/downloadFile.mp3"];

@try {
int read, write;

FILE *pcm = fopen([cafFilePath cStringUsingEncoding:1], "rb");  //source 被转换的音频文件位置
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_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 {

}

}

这样就可以把录制的音频文件压缩成mp3格式的文件了。