Operation Manual

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3.1.3 Controlling Latency by Changing the Buffer Size
Latency in an audio interface can be defined as the time required to process a sample from an application to the
interface’s audio output. A number of factors determine the achievable latency performance of a Hilo/ TB system:
processor speed, operating system, sample rate, number of utilized record or play channels, system efficiency, etc.
Latency can be manipulated by changing the size of the buffers used to transfer data to and from the LT-TB. The
higher the buffer size, the less work the computer has to do to stream audio to the hardware. However, a higher buffer
results in more latency. Also, the higher the sample rate, the higher the buffer size needs to be. For instance, a buffer
size of 128 samples at a sample rate of 44.1 kHz results in 2.9 milliseconds of latency. However, at 96 kHz, a buffer
size of 128 = 1.33 milliseconds. Therefore the buffer size needs to be increased as the sample rate increases to maintain
the same level of performance. If the buffer size is too low, you can experience clicks, pops or distortion in the audio.
This is the result of buffer under-runs, when the audio buffer is momentarily depleted because the computer cannot
deliver samples quickly enough to keep it filled.
Why is latency important? It isn’t in every case. Here are the main conditions where low latency is important:
* Software input monitoring. This is where you are monitoring through your audio software the input signals to be
recorded. The software is re-directing the input signal back out to a play device. If the buffer is too high here the
performer will hear a noticeable delay between the notes they are playing and hearing the sound back through the
computer. With Hilo, zero latency hardware monitoring is available as an alternative to software monitoring. See
Section 3.4.8: Outputs Mix Routing Page.
* Virtual Instruments. Generally this would involve using a software synthesizer or other virtual sound source as an
alternative to dedicated hardware like a keyboard or tone module. Frequently one would play these instruments with
some sort of MIDI controller. The delay between a key being struck and hearing the resulting note from the virtual
instrument is a function of latency.
* Mix Automation. Virtually all DAW applications feature some sort of Mix Automation, and most allow an external
Mix surface or MIDI controller to facilitate mixing within the software environment. Whether using onscreen faders or
a MIDI surface of some sort, latency will determine the delay between manipulating a fader or knob, and that move
being reflected in the project.
3.2 Hilo Driver Devices - Macintosh OS X
Hilo will operate as a Core Audio device under OS X after the driver has been installed. Core Audio is the dominant
audio driver model for OS X, and is used for media playback applications as well as Pro Audio applications.
3.2.1.1 OSX Audio Applications
Hilo can be used as a playback device for most popular multimedia, home theater and pro audio applications. Some
such applications allow selection of specific playback devices. In these cases, a Lynx Hilo TBT output device can be
selected from the appropriate device selection menu.
In cases where the playback software does not provide access to output selections, the default output devices for the
operating system will be used. In OS X, the audio out default device can be established from Applications > Utilities >
Audio MIDI Setup.