录音文件lame转换MP3相关配置

与安卓沟通了一下统一了mp3格式，大小质量都不错。由于AVAudioRecorder录音的格式为.caf或者.wav而且很大需要进行转换压缩为MP3格式。这里需要用到三方库 lame。

使用lame转换后音频的质量和

 _recorder = [[AVAudioRecorder alloc] initWithURL:_recordFilePath settings:setting error:NULL];

里的 setting 息息相关。 所以整理了两个配置。

我把这两种的配置写在了工具类所以直接贴代码了~要用的话直接CV大法就可以。

lame三方库的资源

• 获取转换文件所在文件夹

+ (NSString *)getRecPathUrl{
    NSString *str = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];

    NSString *recordDir = [str stringByAppendingPathComponent:@"RecordCourse"];

    return recordDir;
}

• 获取时间戳用于文件的命名

+ (NSString *)getTimestamp{
    NSDate *nowDate = [NSDate date];
    double timestamp = (double)[nowDate timeIntervalSince1970]*1000;
    long nowTimestamp = [[NSNumber numberWithDouble:timestamp] longValue];
    NSString *timestampStr = [NSString stringWithFormat:@"%ld",nowTimestamp];
    return timestampStr;
}

• PCM转换MP3配置

+ (NSDictionary *)getAudioSettingWithPCM {
    NSMutableDictionary *dic = [NSMutableDictionary dictionary];
    //设置录音格式
    [dic setObject:@(kAudioFormatLinearPCM) forKey:AVFormatIDKey];
    //设置录音采样率，8000是电话采样率，对于一般录音已经够了
    [dic setObject:@(44100.0) forKey:AVSampleRateKey];
    //设置通道,这里采用双声道
    [dic setObject:@(1) forKey:AVNumberOfChannelsKey];
    //每个采样点位数,分为8、16、24、32
    [dic setObject:@(16) forKey:AVLinearPCMBitDepthKey];
    //是否使用浮点数采样
    [dic setObject:@(YES) forKey:AVLinearPCMIsFloatKey];
    //....其他设置等
    return dic;
}

• CAF转换MP3配置

+ (NSDictionary *)getAudioSettingWithCAF {
    NSDictionary *setting = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithInt:AVAudioQualityMin],
                             AVEncoderAudioQualityKey,
                             [NSNumber numberWithInt:16],
                             AVEncoderBitRateKey,
                             [NSNumber numberWithInt:2],
                             AVNumberOfChannelsKey,
                             [NSNumber numberWithFloat:44100.0],
                             AVSampleRateKey,
                             nil];

    return setting;
}

• PCM转换MP3的lame方法

+ (NSString *)audioPCMtoMP3:(NSString *)wavPath {
    NSString *cafFilePath = wavPath;

     大专栏  录音文件lame转换MP3相关配置NSString *mp3FilePath = [NSString stringWithFormat:@"%@.mp3",[NSString stringWithFormat:@"%@%@",[cafFilePath substringToIndex:cafFilePath.length - 4],[self getTimestamp]]];

    NSFileManager* fileManager = [NSFileManager defaultManager];
    if([fileManager removeItemAtPath:mp3FilePath error:nil]){
        NSLog(@"删除原MP3文件");
    }
    @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, 22050.0);
        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 {
        return mp3FilePath;
    }
}

• CAF转换MP3的lame方法

+ (NSString *)audioCAFtoMP3:(NSString *)wavPath {

    NSString *cafFilePath = wavPath;

    NSString *mp3FilePath = [NSString stringWithFormat:@"%@.mp3",[NSString stringWithFormat:@"%@%@",[cafFilePath substringToIndex:cafFilePath.length - 4],[self getTimestamp]]];

    @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_num_channels(lame,1);//设置1为单通道，默认为2双通道
        lame_set_in_samplerate(lame, 44100.0);
        lame_set_VBR(lame, vbr_default);

        lame_set_brate(lame,8);

        lame_set_mode(lame,3);

        lame_set_quality(lame,2);

        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 {
        return mp3FilePath;
    }
}

两种质量大小不错都可以使用????