Is there anyway to properly convert the audio array (float*) into UTF 8?

[cdrandin]

Just wondering if it was possible to somehow turn the array of float values into UTF-8.

I am trying some stuff out that would properly send audio data over a network and play it on another device.

Whenever I try to manipulate the data and receive it on the other end I still end up with floating points.

To put it silly, I kind of need to get it to look like this, bytes

Edit:

More specific what I am trying to do is target a machine that wants to play audio through Port Audio.

[cdrandin]

Actually, NSData didn't help with translating it over properly. Only popping sounds.

How could I transfer or convert float over properly to be played on another device?

[alexbw]

Hey, unfortunately, all Novocaine does is get data off the microphone and give it to you as floats — you'd need to depend on a separate library or build separate code for this functionality.

…

On Mon, Mar 27, 2017 at 4:01 PM cdrandin ***@***.***> wrote: Actually, NSData didn't help with translating it over properly. Only popping sounds. How could I transfer or convert float over properly to be played on another device? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#127 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAJ4jy1gbdK0tAQruqlLPq_1Ie-deyJLks5rqAtYgaJpZM4MosSt> .

[mitisBlack]

@cdrandin NSData is the answer here, UTF8 is meant for text, so that definitely isn't. Given all the points the conversion could go wrong a small sample or code snippets would go a long way to help anyone point the problem(s).

That being said, it sounds like you are trying to put the data in a string then in NSData and then back. This will probably not work as your data is not valid UTF. Either use a NSArchiver or write data directly to the mutableBytes in NSMutableData

[cdrandin]

@mitisBlack Thanks for the info. I will try those out and see what I end up getting.

This is what I am doing on the iOS side of things.
This was taken from the demo to get mic data.

[self.audioManager setInputBlock:^(float *data, UInt32 numFrames, UInt32 numChannels) {
    // send audio data over
    for (int i = 0; i < (sizeof(data)/sizeof(data[0])); ++i) {
        NSMutableData *convertedData = ...;
        
        [[[WampManager sharedInstance] wampConnection] publishTo:@"com.app.audioStream_ios" payload:@{@"payload": convertedData} result:nil];
    }
}];

Now on the other device side, I use Python that gets the data and tries to play it.

import pyaudio

CHUNK = 512
CHANNELS = 2
RATE = 44100
WIDTH = 2

p = pyaudio.PyAudio()
stream = p.open(format=p.get_format_from_width(WIDTH),
                channels=CHANNELS,
                rate=RATE,
                output=True,
                frames_per_buffer=CHUNK)

def audioStream_ios(payload):
    if stream.is_active():
        # print payload
        self.buffer += payload
        # stream.write(payload)
yield self.subscribe(audioStream_ios, 'com.app.audioStream_ios')

while 1:
    print len(self.buffer)
    if stream.is_active() and len(self.buffer) >= CHUNK * 1:
        data = self.buffer[:CHUNK]
        self.buffer = self.buffer[CHUNK:]
        # print 'write'
        # stream.write(data) # play audio data

    yield sleep(0.01)

EDIT:
So I tried this on the iOS side

    NSKeyedArchiver *ka = [[NSKeyedArchiver alloc] init];
    [ka encodeFloat:data[0] forKey:@"0"];
    [ka encodeFloat:data[1] forKey:@"1"];
     // or with
     NSMutableData *d = [NSMutableData dataWithLength:sizeof(float)];
     [d appendBytes:&data length:sizeof(float)];

     [[[WampManager sharedInstance] wampConnection] publishTo:@"com.app.audioStream_ios" payload:@{@"payload": [ka encodedData]} result:nil];

Got pretty bad feedback still. So, not sure if this is done correctly.

I even try writing the raw PCM values to a file to test it out in Audacity. By importing as raw sound and nothing. signed 16bit PCM, big-endian, sample rate: 44100

 NSData *d = [NSData dataWithBytes:&data length: sizeof(data)];
 [wFileHandle writeData:d];

[mitisBlack]

@cdrandin I see. I'll take a closer look later, but a quick look over the code tells me you take the wrong size of the incoming data.

sizeof(data)/sizeof(data[0]) returns the size of the pointer (not memory allocated), so ti will probably just result in 2

try using for size numFrames * numChannels

[cdrandin]

@mitisBlack I tried what you recommended.

I am unsure if this is correct, at least how I am storing into a mutable array.

    NSMutableData *d = [NSMutableData dataWithLength:numFrames * numChannels];
    // or     NSData *d = [NSData dataWithBytes:data length: numFrames * numChannels];

    for (int i = 0; i < numFrames * numChannels; i+=1) {
        [d appendBytes:&data[i] length:sizeof(float)];
    }
    
    NSLog(@"%u", numFrames * numChannels); // 1024
    NSLog(@"%lu", (unsigned long)[d length]); // 8192

    
    [[[WampManager sharedInstance] wampConnection] publishTo:@"com.app.audioStream_ios" payload:@{@"payload": d} result:nil];

All comes back as static feedback. I even was playing with the chunk size and the channels on the Python side to see if that helped.

I printed out the hex values of NSData *d = [NSData dataWithBytes: data length: numFrames * numChannels]; in iOS and I printed over what I was getting sent on the Python side with ''.join(x.encode('hex') for x in payload). They resulted in the same hex values on both sides. So, I am unsure where to go from here. The audio works when I use the methods provided by Novocaine library, but once it gets transported or I write to a file myself. It doesn't work.

[cdrandin]

I have found this example which does a large part of what is needed and I am able to grab the stream. https://github.com/vlider/Mic-recording-minimal-example/blob/master/MicRec/ViewController.swift. Though it is in Swift. I tried writing the raw PCM values directly to file and still came back awful.

So, seems AVAudioEngine may be another choice worth checking out. As I am simply just trying to get it working at this point.