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What do the Audio Info settings in iConfig mean?


If you open iConfig and look under Audio Info you'll see several different settings you can change. Some of them are pretty important, some not so important, but it can be useful to know what they all mean.

The first setting Number of audio ports is fixed - that's set by your interface and simply tells you how many sets of audio Inputs and Outputs it has. On the iConnectAudio4+ shown above, that's 3 ports: USB1USB2, and Analog.

Buffered Audio Frames and Sync Factor Value

Now we come to two of the more arcane settings: Number of buffered audio frames and Sync factor value. You won't find these on any other interfaces because they are used for iConnectivity's patented ability to connect more than one USB device at a time. To allow audio to pass between USB device ports we need to manage the data flow. The host computer or iOS devices operate on their own clock domains and are not synchronized together. To avoid missed samples (which result in audio clicks) we need to buffer a small amount of audio in our box to synchronize the data flow between the host devices. These two parameters affect how well audio synchronization is handled inside our interfaces.

1. Number of buffered audio frames
USB audio data is packetized into frames. The Number of buffered audio frames parameter sets the number of "super-frames" that our box will buffer from host #1 before passing data to host #2 (and vice versa). A super-frame is 1 millisecond on iCM products and 500 microseconds on iCA products. Lower numbers are better because they provide slightly lower latency and faster response time while recording. The default value of 3 works for most systems. On rare occasions you may need to increase this to 4 or 5 to avoid audio clicking - depends on the host.

2. Sync factor value
The Sync factor value parameter is used in an internal calculation for matching clock rates between hosts. For iCM products this affects how quickly the synchronization code reacts to sudden changes in clock rate. Think of it as a low pass filter where higher values are a lower cutoff value (more smoothing). For iCA products this has almost no effect, so if you have one of those boxes just ignore this. For iCM units the default value should work for most host computers and iOS devices but higher values may help improve synchronization with some problematic hosts.

In general however, you will probably never need to touch either of these values.

Audio Configuration

The Audio configuration setting, however, is very important indeed, as it directly affects the sound you are recording. The default value set at the factory is 44100HZ, 16bit. This is far from the best sound quality for recording, but is set like this for maximum compatibility, since many iOS audio apps can only operate in this mode. If you are making music on a modern computer Digital Audio Workstation I strongly advise you to change this setting to the one shown above: 44100Hz, 24bit. This will give your recorded audio much higher dynamic range and a cleaner sound. If you are working with video material you'll probably want to change it to 48000Hz, 24bit, since most AV material runs at a sample rate of 48k. Some people may even want to go up to a high sample rate of 96000Hz, 24bit, but it is debatable whether this is really worth it for most applications.

Clock Source

The last setting shown refers to the Clock source. Please note this is nothing to do with MIDI Clock signals that you might use to synchronise MIDI devices like drum machines and sequencers. This refers to the clock signal used to keep all of your digital audio signals coherent. You can choose to have this clock come from one of your computing devices on USB port 1 or USB port 2, or you can choose Internal Clock as in the screenshot above. In 99 cases out of 100 Internal Clock is going to be your optimal choice. However in very rare cases you might need to switch this to one of the USB ports instead, which is why the option exists. However the chances are that won't happen.

Bottom line: set your Audio Configuration and Clock Source the way you need them and you'll probably never have to touch them again - it's that simple. Happy recording!