GS2972 Datasheet, PDF (45/125 Pages) Semtech Corporation – 3G/HD/SD-SDI Serializer with Complete SMPTE Audio & Video Support

4.7 Audio Embedding
The GS2972 includes an Audio Multiplexer, which by default will be active when the
Transmitter is configured for SMPTE mode.
Audio embedding is controlled by:
• GRP1_EN/DIS and GRP2_EN/DIS pins are set HIGH to enable embedding of their
respective groups
• The AUDIO_INS bit in the IOPROC register is set LOW to enable audio embedding
• The IOPROC_EN/DIS pin is set HIGH to enable audio embedding
In non-SMPTE modes, the Audio Multiplexer will be powered down to reduce power.
Note: When audio is embedded by the GS2972, if either of the GRP1_EN/DIS or
GRP2_EN/DIS pins are toggled, the output video stream is lost. For example: With a
3Gb/s SDI Level A input signal as the source, and either AES or I²S mode audio
embedded; if one of the audio groups is disabled, there is no a longer valid video signal
present at the output.
Toggling the audio disable pins on the fly must be avoided. The user has to set the pins
before resetting the chip, and not change the setting during normal operation. The audio
may be enabled or disabled during the operation of the chip by writing to the Host
Interface registers. SD audio group embedding may be enabled, or disabled, by writing
to ACT1...ACT8 bits of register 40Fh. HD/3G audio group embedding may be enabled, or
disabled, by writing to ACT1...ACT8 bits of register 80Eh.
4.7.1 Serial Audio Data Inputs
The GS2972 supports the insertion of up to 8 channels of embedded audio, in two groups
of 4 channels.
Each audio group has a dedicated audio group enable input pin; a Word Clock (WCLK)
input pin operating at 48kHz; an Audio Clock input pin (ACLK) operating at 3.072MHz
(64 x WCLK); and two serial digital audio input pins (AIN_1/2, etc.), supporting one
stereo audio signal pair per pin.
The Serial Audio Data Inputs for each audio group are listed in Table 4-5.
Table 4-5: Serial Audio Input Pin Description
Pin Name
Description
GRP1_EN/DIS
AIN_1/2
AIN_3/4
ACLK1
WCLK1
Audio Group 1
Enable Input for Audio Group 1
Serial Audio Input; Channels 1 and 2
Serial Audio Input; Channels 3 and 4
64 x WCLK associated with AIN_1/2 and AIN_3/4
(channels 1, 2, 3and 4)
48kHz Word Clock associated with AIN_1/2 and AIN_3/4
(channels 1, 2, 3 and 4)
GS2972 3G/HD/SD-SDI Serializer with Complete
SMPTE Audio & Video Support
Final Data Sheet Rev. 9
GENDOC-047479 September 2013
www.semtech.com
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