User's Manual
D-Cam Clip-On Operators Manual Issue 1 Page 22 of 22
UNUM-CCAM -0104
5.2 Audio / Video Encoder
The Encoder board consists of the following main functions:
• SDI to Digital deserialiser. Converts the SMPTE-259M-C serial digital video
input to an 8 bit parallel digital video bus.
• Analogue to Digital Video Converter, 10-bit over sampling ADC. Takes either
Composite Video (75 ?, 1v p-p) (CVBS); YC or YUV inputs in either PAL /
NTSC format and converts to an 8-bit parallel digital video bus.
• Analogue to Digital Audio Converter, 48kHz, 24 bit
Two high impedance analogue inputs. Audio 1 (or left channel). Audio 2 (or
right channel). The two channels are first buffered by a variable gain stage to
cater for either Mic or Line level inputs. A switchable 20dB stage is also
included to cater for low level Mic inputs. The two audio channels are then
converted into an I
2
S serial data stream.
• FPGA. Selects the required 8 bit-parallel digital video bus from either the SDI
deserialiser or the video ADC for input to the MPEG2 encoder, a relay is used to
route the input from the BNC (either SDI or CVBS) to either the deserialiser or
ADC.
• Microcontroller. Writes control data and reads status data to/from the MPEG2
Encoder.
• MPEG2 Encoder
A suite of MPEG2 compliant compression techniques, where the data bit rate is
reduced by processing over multiple picture frames. The absolute picture (Intra
frame) is interleaved with pictures that are created using difference data
(Predicted frame) with Bi-directionally predicted frames (4:2:2 Only) in
conjunction with motion compensation; thus low data rates down to 6 Mbps, can
be achieved.
A set of encoding parameters is loaded into the encoder at power up. These
are selected from one of the ‘preset’ encoder memories. See 3.2.4
• DC Power Supplies
Switching DC/DC converters are used to generate the various supplies from the
incoming 9-18V battery supply. These include 2.5, 3.3V, 5V, 8V and +/-5V
supplies.
There are no field replaceable parts on the Encoder board. If a fault occurs with the board,
contact Gigawave for technical assistance.