How to add playable(such as wav,wmv) header with PCM data/buffer in iOS?

Question

I am trying to add a wav header on top of raw PCM data to make it playable via AVAudioPlayer. But i couldn\'t find any solution or source code to do that on iOS using Object

Answer 1

OK, I am answering my own question if it helps someone else. After few days of tireless trying, at last i have got it working. Below is a complete Function written with Objective-C and C. It takes a file path as a parameter which contains RAW PCM data directly captured from microphone and returns a file path which contains PCM data followed by appropriate wav header info. Then you can play that file with AVAudioPlayer or AVPlayer. Here is the code...

- (NSURL *) getAndCreatePlayableFileFromPcmData:(NSString *)filePath
{
    NSString *wavFileName = [[filePath lastPathComponent] stringByDeletingPathExtension];
    NSString *wavFileFullName = [NSString stringWithFormat:@"%@.wav",wavFileName];

    [self createFileWithName:wavFileFullName];
    NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *docsDir = [dirPaths objectAtIndex:0];
    NSString *wavFilePath = [docsDir stringByAppendingPathComponent:wavFileFullName];

    NSLog(@"PCM file path : %@",filePath);

    FILE *fout;

    short NumChannels = AUDIO_CHANNELS_PER_FRAME;
    short BitsPerSample = AUDIO_BITS_PER_CHANNEL;
    int SamplingRate = AUDIO_SAMPLE_RATE;
    int numOfSamples = [[NSData dataWithContentsOfFile:filePath] length];

    int ByteRate = NumChannels*BitsPerSample*SamplingRate/8;
    short BlockAlign = NumChannels*BitsPerSample/8;
    int DataSize = NumChannels*numOfSamples*BitsPerSample/8;
    int chunkSize = 16;
    int totalSize = 46 + DataSize;
    short audioFormat = 1;

    if((fout = fopen([wavFilePath cStringUsingEncoding:1], "w")) == NULL)
    {
        printf("Error opening out file ");
    }

    fwrite("RIFF", sizeof(char), 4,fout);
    fwrite(&totalSize, sizeof(int), 1, fout);
    fwrite("WAVE", sizeof(char), 4, fout);
    fwrite("fmt ", sizeof(char), 4, fout);
    fwrite(&chunkSize, sizeof(int),1,fout);
    fwrite(&audioFormat, sizeof(short), 1, fout);
    fwrite(&NumChannels, sizeof(short),1,fout);
    fwrite(&SamplingRate, sizeof(int), 1, fout);
    fwrite(&ByteRate, sizeof(int), 1, fout);
    fwrite(&BlockAlign, sizeof(short), 1, fout);
    fwrite(&BitsPerSample, sizeof(short), 1, fout);
    fwrite("data", sizeof(char), 4, fout);
    fwrite(&DataSize, sizeof(int), 1, fout);

    fclose(fout);

    NSMutableData *pamdata = [NSMutableData dataWithContentsOfFile:filePath];
    NSFileHandle *handle;
    handle = [NSFileHandle fileHandleForUpdatingAtPath:wavFilePath];
    [handle seekToEndOfFile];
    [handle writeData:pamdata];
    [handle closeFile];

    return [NSURL URLWithString:wavFilePath];
}

But that function only works with the following audio settings.

// Audio settings.
#define AUDIO_SAMPLE_RATE 8000
#define AUDIO_FRAMES_PER_PACKET 1
#define AUDIO_CHANNELS_PER_FRAME 1
#define AUDIO_BITS_PER_CHANNEL 16
#define AUDIO_BYTES_PER_PACKET 2
#define AUDIO_BYTES_PER_FRAME 2

Answer 2

Very helpful question and answer, thank you very much.

This swift version is for those in need:

static func createWAV(from pcmFilePath: String, to wavFilePath: String) -> Bool {

    // Make sure that the path does not contain non-ascii characters
    guard let fout = fopen(wavFilePath.cString(using: .ascii), "w") else { return false }

    guard let pcmData = try? Data(contentsOf: URL(fileURLWithPath: pcmFilePath)) else { return false }

    var numChannels: CShort = 1
    let numChannelsInt: CInt = 1
    var bitsPerSample: CShort = 16
    let bitsPerSampleInt: CInt = 16
    var samplingRate: CInt = 16000
    let numOfSamples = CInt(pcmData.count)
    var byteRate = numChannelsInt * bitsPerSampleInt * samplingRate / 8
    var blockAlign = numChannelsInt * bitsPerSampleInt / 8
    var dataSize = numChannelsInt * numOfSamples * bitsPerSampleInt / 8
    var chunkSize: CInt = 16
    var totalSize = 46 + dataSize
    var audioFormat: CShort = 1

    fwrite("RIFF".cString(using: .ascii), MemoryLayout<CChar>.size, 4, fout)
    fwrite(&totalSize, MemoryLayout<CInt>.size, 1, fout)
    fwrite("WAVE".cString(using: .ascii), MemoryLayout<CChar>.size, 4, fout);
    fwrite("fmt ".cString(using: .ascii), MemoryLayout<CChar>.size, 4, fout);
    fwrite(&chunkSize, MemoryLayout<CInt>.size,1,fout);
    fwrite(&audioFormat, MemoryLayout<CShort>.size, 1, fout);
    fwrite(&numChannels, MemoryLayout<CShort>.size,1,fout);
    fwrite(&samplingRate, MemoryLayout<CInt>.size, 1, fout);
    fwrite(&byteRate, MemoryLayout<CInt>.size, 1, fout);
    fwrite(&blockAlign, MemoryLayout<CShort>.size, 1, fout);
    fwrite(&bitsPerSample, MemoryLayout<CShort>.size, 1, fout);
    fwrite("data".cString(using: .ascii), MemoryLayout<CChar>.size, 4, fout);
    fwrite(&dataSize, MemoryLayout<CInt>.size, 1, fout);
    fclose(fout);

    guard let handle = FileHandle(forUpdatingAtPath: wavFilePath) else { return false }

    handle.seekToEndOfFile()
    handle.write(pcmData)
    handle.closeFile()

    return true
}