如何将采样率 16000 的 wav 转换为 mp3？答案

【问题标题】：How to convert wav to mp3 for samplerate 16000?如何将采样率 16000 的 wav 转换为 mp3？
【发布时间】：2017-07-28 14:33:26
【问题描述】：

我正在尝试使用 Samplerate 16000 将 wav 文件转换为 mp3。转换后的音频质量不好，而且速度似乎有所提高。如果音频转换采样率设置为 8000，效果很好。我已经创建了 Wav 到 mp3 的方法：

+(void)convertFromWavToMp3:(NSString *)filePath FileName:(NSString *)kFileName SampleRate:(int)kSampleRate failAction:(WavToMp3CompletionBlock)failBlock successAction:(WavToMp3CompletionBlock)successBlock

{

NSLog(@"%@", [filePath stringByDeletingLastPathComponent]);

NSString *mp3FileName = kFileName;
mp3FileName = [mp3FileName stringByAppendingString:@".mp3"];
NSString *mp3FilePath = [[filePath stringByDeletingLastPathComponent] stringByAppendingPathComponent:mp3FileName];

NSLog(@"%@", mp3FilePath);

@try {
    int read, write;

    NSFileManager *filemgr;
    filemgr = [NSFileManager defaultManager];
    char const *path_cstr = [filemgr fileSystemRepresentationWithPath:filePath];

    FILE *pcm = fopen(path_cstr, "rb");  //source
    fseek(pcm, 4*1024, SEEK_CUR);                                   //skip file header
    FILE *mp3 = fopen([mp3FilePath cStringUsingEncoding:1], "wb");  //output

    const int PCM_SIZE = 16384;
    const int MP3_SIZE = 16384;
    short int pcm_buffer[PCM_SIZE*2];
    unsigned char mp3_buffer[MP3_SIZE];

    lame_t lame = lame_init();
    lame_set_in_samplerate(lame, 8000);
    lame_set_num_channels(lame, 1);
    lame_set_VBR(lame, vbr_default);
   // lame_set_brate(lame, 128);

    lame_set_quality(lame, 0);
    lame_set_brate(lame, 128);

    lame_set_num_samples(lame, 8000);
    lame_set_out_samplerate(lame, 8000);
    lame_set_mode(lame, 3);

    lame_init_params(lame);

    lame_print_config(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);
    successBlock(true);
}
@catch (NSException *exception) {
    NSLog(@"%@",[exception description]);
    failBlock(false);
}
@finally {

}

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标签： ios audio mp3 wav lame

【解决方案1】：

为了将波形转换为 mp3 使用可以使用 ExtAudioFileConverter 类： https://github.com/lixing123/ExtAudioFileConverter

用于转换 mp3 采样率 16000：

ExtAudioConverter* converter = [[ExtAudioConverter alloc] init];
converter.outputSampleRate = 16000;
converter.outputNumberChannels = 2;
converter.outputBitDepth = BitDepth_16;
converter.outputFormatID = kAudioFormatLinearPCM;
converter.outputFileType = kAudioFileMP3Type;

converter.inputFile =  @"Desktop/input.wav";
converter.outputFile = @"Desktop/output.mp3";
[converter convert];

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