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Editorial Team
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Asked: 2026-06-03T15:49:22+00:00

How do I encode audio to u-law g.711? Then send that audio to a

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How do I encode audio to u-law g.711? Then send that audio to a remote server via http.

AUDIO STREAM: Send a continuous stream of audio to the
currently viewed camera. Audio needs to be encoded at G711 mu-law at
64 kbit/s for transfer to the Axis camera at the bedside. send (this
should be a POST URL in SSL to connected server): POST
/transmitaudio?id= Content-type: audio/basic
Content-Length: 99999 (length is ignored)

I have searched on google and on here but mostly what I find are ways to stream from a server to an I device and not the other way around. I did find this posting (http://stackoverflow.com/questions/7750329/how-to-send-audio-file-through-http-post-to-a-server-from-ios) however it seems likes the answers are not very descriptive nor has any of them been accepted.

Here is what I have so far.

{
        NSNumber *formatObject;

        switch (self.recordEncoding) {
            case (ENC_AAC): 
                formatObject = [NSNumber numberWithInt: kAudioFormatMPEG4AAC];
                break;
            case (ENC_ALAC):
                formatObject = [NSNumber numberWithInt: kAudioFormatAppleLossless];
                break;
            case (ENC_IMA4):
                formatObject = [NSNumber numberWithInt: kAudioFormatAppleIMA4];
                break;
            case (ENC_ILBC):
                formatObject = [NSNumber numberWithInt: kAudioFormatiLBC];
                break;
            case (ENC_ULAW):
                formatObject = [NSNumber numberWithInt: kAudioFormatULaw];
                break;
            default:
                formatObject = [NSNumber numberWithInt: kAudioFormatAppleIMA4];
        }

        [recordSettings setObject:formatObject forKey: AVFormatIDKey];
        [recordSettings setObject:[NSNumber numberWithFloat:44100.0] forKey: AVSampleRateKey];
        [recordSettings setObject:[NSNumber numberWithInt:2] forKey:AVNumberOfChannelsKey];
        [recordSettings setObject:[NSNumber numberWithInt:12800] forKey:AVEncoderBitRateKey];
        [recordSettings setObject:[NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey];
        [recordSettings setObject:[NSNumber numberWithInt: AVAudioQualityHigh] forKey: AVEncoderAudioQualityKey];
    }

This appears to be U-law (hence the name of the encode), however I know nothing about audio codecs and dont know if G711 mu-law is even possible on ios.
How do I get my audio encoded in the right format?

Then how to send that encoded audio to the server? Right now I have it going to a temporary file location but even if I changed that I dont see how that would help. I know this is alot to ask for and I’m not looking to have an answer given to me, but I need a place to start because at the moment I’m fairly lost as to how to do this.

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1 Answer

  1. Editorial Team

    This sends the audio after it is done recording

     self.request = [client multipartFormRequestWithMethod:@"POST" path:[NSString stringWithFormat:@"transmitaudio?id=%@",self.restClient.sessionId] parameters:parameters constructingBodyWithBlock: ^(id <AFMultipartFormData>formData) 
                    {
                        NSError * error = [[NSError alloc]init];

                        [formData appendPartWithFileURL:self.audioHandler.soundFileURL name:@"sound.caf" error:&error];
                        //            NSLog(@"error %@", [error localizedDescription]);
                    }];

    AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:self.request];

    [self.queue addOperation:operation];
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