How to convert wav to mp3 for samplerate 16000?

Question

I'm trying to make conversion from wav file to mp3 using Samplerate 16000. After converting the quality of the audio is not good and its speed seems like an increased. Where as it worked well if the audio conversion sample rate set to 8000. I have created the method for Wav to mp3:

+(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 {

}

Please check my answer. – Saurabh Jain Jul 31 '17 at 17:00 — Saurabh Jain, Jul 31 '17 at 17:00
is my answer helpful for you? – Saurabh Jain Aug 28 '17 at 15:35 — Saurabh Jain, Aug 28 '17 at 15:35

score 2 · Answer 1 · answered Jul 28 '17 at 16:32

For converting wave to mp3 use can use the ExtAudioFileConverter class : https://github.com/lixing123/ExtAudioFileConverter

For converting mp3 sample rate 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];

How to convert wav to mp3 for samplerate 16000?

1 Answers1