根据pcm文件转MP3
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(void)conventToMp3 {
NSString *cafFilePath = [NSTemporaryDirectory() stringByAppendingString:@"VoiceInputFile"];
self.mp3FilePath = [[NSUUID UUID] UUIDString];
self.mp3FilePath = [self.mp3FilePath stringByAppendingString:@".mp3"];
NSString *mp3FilePath = [[NSHomeDirectory() stringByAppendingFormat:@"/Documents/"] stringByAppendingPathComponent:self.mp3FilePath];@try {
int read, write; FILE *pcm = fopen([cafFilePath cStringUsingEncoding:NSASCIIStringEncoding], "rb"); FILE *mp3 = fopen([mp3FilePath cStringUsingEncoding:NSASCIIStringEncoding], "wb"); 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, self.sampleRate); lame_set_VBR(lame, vbr_default); lame_init_params(lame); long curpos; BOOL isSkipPCMHeader = NO; do { curpos = ftell(pcm); long startPos = ftell(pcm); fseek(pcm, 0, SEEK_END); long endPos = ftell(pcm); long length = endPos - startPos; fseek(pcm, curpos, SEEK_SET); if (length > PCM_SIZE * 2 * sizeof(short int)) { if (!isSkipPCMHeader) { //Uump audio file header, If you do not skip file header //you will heard some noise at the beginning!!! fseek(pcm, 4 * 1024, SEEK_SET); isSkipPCMHeader = YES; } read = (int)fread(pcm_buffer, 2 * sizeof(short int), PCM_SIZE, pcm); write = lame_encode_buffer_interleaved(lame, pcm_buffer, read, mp3_buffer, MP3_SIZE); fwrite(mp3_buffer, write, 1, mp3); } else { [NSThread sleepForTimeInterval:0.05]; } } while (!self.isStopRecorde); read = (int)fread(pcm_buffer, 2 * sizeof(short int), PCM_SIZE, pcm); write = lame_encode_flush(lame, mp3_buffer, MP3_SIZE); lame_close(lame); fclose(mp3); fclose(pcm); self.isFinishConvert = YES;}
@catch (NSException *exception) {}
@finally {}
}
参数设置
/** mp3压缩参数 /
_lame = lame_init();
/* 单声道 /
lame_set_num_channels(_lame, 1);
/* 16K采样率 决定 音质 清晰度 /
lame_set_in_samplerate(_lame, 16000);
lame_set_out_samplerate(_lame, 16000);
/* 压缩的比特率为16K 决定mp3 文件大小 */
lame_set_brate(_lame, 16);
仔细阅读以下博客 你会有所收获
实时格式化pcm --> mp3
http://code4app.com/forum.php?mod=viewthread&tid=6211
http://www.cnblogs.com/ios8/p/IOS-PCM-MP3.html
边录边转详解
