Hello 
,
I am new to Juce, and I’m trying to develop a program where I can stream the inputs from my audio interface to another audio interface over my local network.
Concretely, I have Computer A with audio interface A and Computer B with audio interface B. And I want that whatever audio that is captured on input channel 1 on the audio interface A is sent to output channel 1 on audio interface B. (and vice versa)
I decided to use Juce for this, as it seemed very practical to control audio interfaces. So what I did is I created a standalone Audio Application with the Projucer. And I followed the tutorial on OSCReceiver / Sender to create my network communication and send my Audio Buffers.
So my implementation is as follows:
-
In
getNextAudioBlock()of myMainComponent, I get the input buffer (I have only one channel active) and pass the raw input buffer to myConnectionManager(which sends it) like this//================================= LOCAL INPUTS ================================= int i = 0; // Used for sending to the corresponding freq diagramm component for (auto inputChannel = 0; inputChannel < maxInputChannels; inputChannel++) { if (! activeInputChannels[inputChannel]) // Individual input channels may be inactive so we don't want to store the data { bufferToFill.buffer->clear (inputChannel, bufferToFill.startSample, bufferToFill.numSamples); } else { // Here we get pointer to the input and send it to the network auto* inBuffer = bufferToFill.buffer->getReadPointer (inputChannel, bufferToFill.startSample); // If we are connected, we send data to the distant instance and we play the data if(networkManager.isConnected()){ networkManager.sendAudioBuffer(i, inBuffer, bufferToFill.numSamples); } i++; } } -
In my
sendAudioBuffer()function of myNetworkManager, I create an OSC message object where I add the channel (ch0) as an Int argument and then I add all the samples of the buffer as Float arguments (e.g with buffer size 512 the message has a length of 513)
juce::OSCMessage msg(juce::OSCAddressPattern("/creepy-table")); // Declare and initialize message
msg.addArgument(juce::OSCArgument(inputID)); // Add the channel id
for(int i=0; i<bufferSize; ++i){
msg.addArgument(juce::OSCArgument(buffer[i])); // Add every sample
}
- My
NetworkManagerimplementsOSCReceiverand in theoscMessageReceived()method, (on the other machine) I get the message get the channel and buffer out and put it in ajuce::AudioBuffer
void NetworkManager::processOSCMessage(juce::OSCMessage message){
if (message.size() > 2){
// Case where it starts with int, then it's an audio buffer with first argument as channel
if (message[0].isInt32()){
int channel = message[0].getInt32(); // Declare channel to use
// Channel has to be positive and msg length has to be inferior or equal to buffer size
if (channel >= 0 && message.size()-1 <= distantAudioBuffer->getNumSamples()) {
juce::Array<float> buffer; // Declare a temporary buffer for practicality
for (int i=1; i<message.size(); ++i){ // Starts at 1 because in this formatted OSC messsages the float arguments start after 1 (0 is for channel)
if (message[i].isFloat32()) buffer.add(message[i].getFloat32());
}
distantAudioBuffer->copyFrom(channel, 0, buffer.data(), buffer.size()); // Put the samples in distantAudioBuffer then used by distantAudioSource object in mainComponent
}
}
}
}
- The same
AudioBufferis then read ingetNextAudioBlock()and the content of my distant received buffer is copied in theoutBufferto be played
auto* outBuffer = bufferToFill.buffer->getWritePointer (outputChannel, bufferToFill.startSample); // Buffer to output
auto* distantBuffer = distantAudioBuffer.getReadPointer(outputChannel); // Distant input buffer
for (auto sample = 0; sample < bufferToFill.numSamples; ++sample)
outBuffer[sample] = distantBuffer[sample];
So it kinda works, I manage to send and receive the messages, however my problem is that the signal received is …weird. I tried to send the signal from an electric guitar connected to my audio interface A, and basically it sounds horrible. Notes are still somehow recognisable, but there is a huge buzzing sound on top whenevever there is sound to be played.
(If you want to listen to it you can check it here, but it’s horrible)
https://sndup.net/9zxn
I display (like on of the juce tutorials does) the signal I output to the speakers. And it looks similar to the signal originally sent, but the received signal looks imprecise. I don’t know if my weird sound comes from this.
I am a bit stuck, and I’m not sure how to fix my issue as I don’t have much experience in audio processing and Juce. 
- Does the use of OSCMessages make sense to send Audio Buffers via network? Does it even make sense to send Audio Buffers?
- Do you have an idea why the received signal looks less accurate and sharp then what is originally sent? Could it be from the way I read my buffer?
As additional infos: I use a samplerate of 44100Hz and buffer size of 512 with bit depth of 24
If someone could help me figure out ways to continue, or give hints / opinions on the methods I use / my implementation, it would be greatly appreciated
Cheers,
P
And there are even more, OSC unrelated things to consider:
) as this might block code execution for a non-deterministic time, depending on a lot of reasons. Performing heap memory allocation (e.g. using Strings, HeapBlocks etc. – you’ll find plenty of them if you look inside the OSC classes) as these memory resources are managed by the operating system, which might be busy and not respond to your call as soon as possible or might decide to swap out ram to your hard drive at some point. Waiting for locks held by other threads… you never know when the other thread will have finished its work and if its thread priority is lower then your super high priority audio thread this will cause so called priority inversion.
