Objective-c - How to serialize audio file into small packets that can be played?

Posted by vfn on Stack Overflow See other posts from Stack Overflow or by vfn
Published on 2010-03-08T05:38:52Z Indexed on 2010/03/08 11:06 UTC
Read the original article Hit count: 501

Hi there,

So, I would like to get a sound file and convert it in packets, and send it to another computer. I would like that the other computer be able to play the packets as they arrive.

I am using AVAudioPlayer to try to play this packets, but I couldn't find a proper way to serialize the data on the peer1 that the peer2 can play.

The scenario is, peer1 has a audio file, split the audio file in many small packets, put them on a NSData and send them to peer2. Peer 2 receive the packets and play one by one, as they arrive.

Does anyone have know how to do this? or even if it is possible?

EDIT:

Here it is some piece of code to illustrate what I would like to achieve.


// This code is part of the peer1, the one who sends the data
- (void)sendData
{
    int packetId = 0;
    NSString *soundFilePath = [[NSBundle mainBundle] pathForResource:@"myAudioFile" ofType:@"wav"];

    NSData *soundData = [[NSData alloc] initWithContentsOfFile:soundFilePath];
    NSMutableArray *arraySoundData = [[NSMutableArray alloc] init];

    // Spliting the audio in 2 pieces
    // This is only an illustration
    // The idea is to split the data into multiple pieces
    // dependin on the size of the file to be sent
    NSRange soundRange;
    soundRange.length = [soundData length]/2;
    soundRange.location = 0;
    [arraySoundData addObject:[soundData subdataWithRange:soundRange]];
    soundRange.length = [soundData length]/2;
    soundRange.location = [soundData length]/2;
    [arraySoundData addObject:[soundData subdataWithRange:soundRange]];

    for (int i=0; i
// This is the code on peer2 that would receive an play the piece of audio on each packet

- (void) receiveData:(NSData *)data
{

    NSKeyedUnarchiver* unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];

    if ([unarchiver containsValueForKey:PACKET_ID])
        NSLog(@"DECODED PACKET_ID: %i", [unarchiver decodeIntForKey:PACKET_ID]);

    if ([unarchiver containsValueForKey:PACKET_SOUND_DATA])
    {
        NSLog(@"DECODED sound");
        NSData *sound = (NSData *)[unarchiver decodeObjectForKey:PACKET_SOUND_DATA];

        if (sound == nil)
        {
            NSLog(@"sound is nil!");

        }
        else
        {
            NSLog(@"sound is not nil!");

            AVAudioPlayer *audioPlayer = [AVAudioPlayer alloc];

            if ([audioPlayer initWithData:sound error:nil])
            {
                [audioPlayer prepareToPlay];
                [audioPlayer play];
            } else {
                [audioPlayer release];
                NSLog(@"Player couldn't load data");
            }   
        }
    }

    [unarchiver release];
}

So, here is what I am trying to achieve...so, what I really need to know is how to create the packets, so peer2 can play the audio.

It would be a kind of streaming. Yes, for now I am not worried about the order that the packet are received or played...I only need to get the sound sliced and them be able to play each piece, each slice, without need to wait for the whole file be received by peer2.

Thanks!

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