Click the Audio Mixer tab (centered in the lower third of the Live Desktop) to reveal audio features, including configuration controls for all internal and external audio sources and outputs, including streaming.
Each input has its own small control panel, with Volume slider(s), VU meter(s), and other important features conveniently located. At the top of each of these control panels is a label.
Roll the mouse pointer over the label to reveal a gear button at right which, when clicked, opens the Configuration panel (Figure 28) for the input.
Click the source menu at the top of the panel to display connection options for an input (Figure 28). Audio options are similar to video, in that you will see local hardware inputs (shown as “IN 1”, “IN 2”, etc.) along with network sources, including both NDI audio and (Audinate™) Dante sources.
Generally, hardware inputs default to “line level”. As when configuring video inputs, choosing a local hardware audio source causes a configuration ‘gear’ icon to be displayed at right. Again, clicking the gear opens the Hardware Configuration panel. In this case, you will need to use the menu in the Audio Source column for the input you are configuring to choose an appropriate connection type, such as Line, Microphone, or perhaps SDI or HDMI (Figure 29 – options vary by model).
Note: Analog audio levels conform to SMPTE RP-155. The maximum input/output level is +24 dBu, nominal Mic input level +4 dBu (-20dBFS), and the sample rate is 96 kHz.
- Select Mic for professional grade microphones or similar sources. On supporting models, use the Phantom option for condenser type microphones requiring supplementary power.
- Choose Line for most other analog sources (including consumer devices such as a CD player, computer audio output or VCR).
- For 4RU models only, select AES/EBU for digital audio from an AES/EBU (AES3) source.
- SDI Embedded or HDMI provide digital audio from the associated video connection.
Hint: Some variation exists as respects signal levels from individual sources, even within the same type. For Mic (and Mic + Phantom) connections, Gain (a.k.a., Trim) controls are provided to allow fine tuning of the input level.
Returning to the audio Input Configuration panel (Figure 28), note that it holds both basic and advanced audio features. In the former category, volume sliders are provided below VU meters for each audio source and output. Source sliders default to their lowest setting on first launch. After adding audio sources, slowly bring these sliders up to pass their respective signals through the system.
Hint: Most numeric controls in TriCaster can be reset to their defaults using Shift + double-click on the control knob. The default value for Gain sliders is 0dBVU.
In digital audio systems, levels exceeding ‘legal’ values are ‘clipped’ (uniformly assigned the maximum value). This results in audible issues that cannot be easily corrected later. For this reason, it’s customary to configure normal operating level (also referred to as the ‘alignment level’, and sometimes, ‘nominal level’) well below the clipping limit – sufficiently so that occasional excessively loud sounds (say, loud laughter or applause) can be accommodated without risk.
This range above between nominal level and the highest possible level is commonly referred to as ‘audio headroom’. What is considered a suitable headroom allowance can vary from one locale to another, in different industry applications, and even in individual studios. TriCaster’s audio controls follow well-established conventions, providing 20dB of headroom above nominal level (+4dBu at 0dB on the VU scale).
Hint: Confusion can sometimes arise because different calibration scales are common in various audio realms, and even for different device types and software. For example, analog mixers commonly show levels on VU scales indexed as just described. In contrast, digital devices and editing software usually display levels in dBFS (Decibels Full Scale) with 0dBFS – the absolute maximum signal level that can be recorded – at the top. TriCaster’s VU meters have selectable indexing, allowing you to view a traditional dB VU scale or dBFS as you please (see Section 15.8.1).
Whatever scale you choose, use Volume controls (and, for Mic connections, the Gain controls in the Configuration panel) to avoid over-modulation. TriCaster’s Compressor/Limiter feature (also located in the Audio Configuration panel) is another powerful tool to help you prevent clipping – see Section 15.7
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