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One sample rate converter
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Three encoders
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One set of audio outputs
Audio inputs front-end
The audio multiplexer selects a digital audio stream from one of the following three audio
sources:
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Analog audio source
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SDI audio source
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HDMI audio source
The analog audio interface digitizes the analog audio stereo signal at 48 kHz.
The HDMI and SDI interfaces extract up to two audio channels of the embedded audio/video
signal. The sampling rate for such audio signal is determined by the HDMI/HD-SDI source.
Sampling rate converter
The sample rate converter adapts the sample rate of the audio stream to the desired rate.
The sample rate is defined once for all the encoded audio streams and the audio outputs. If e.g.
we want to use G.711 encoder (8kHz), simultaneous output as linear PCM or AAC is only possible
at 8kHz!
Audio encoders
There are 3 audio encoders: one G.7xx encoder, one AAC encoder and one Linear PCM encoder.
Up to 3 encoders can be used providing that they are requiring the same sampling rate. This is
tested and enforced by the web service layer, that will not allow simultaneous use of two
encoders requiring conflicting sampling rates.
Important side-effect: producing G.711 out of de-embedded audio might thus be available only
when embedded audio is sampled by the source at 8kHz.
Audio outputs set
The audio stream can feed:
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Two digital audio channels of the HDMI Output
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Left and Right channels of the analog audio output through a stereo DAC converter.
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