NCast Presentation Recorder Reference Manual
2.2. C
APTURE
M
ODULE
F
UNCTION
The capture module selects one of the available six inputs (VGA, DVI-D, DVI-A, HDMI, Composite, S-Video)
and locks onto the signal. The signal is converted into the appropriate digital formats, and each pixel in the
image is stored in a local memory buffer on the module. Any required sizing and re-scaling is done in the
module. At an appropriate time the pixels in module are transferred to the DSP where they are processed
and compressed.
If PIP mode is enabled, two signals may be selected (exceptions: Composite and S-video share one video
decoding chip and are the same signal, VGA and DVI-A share one input chip and are the same signal).
2.3. C
OMPRESSION
The digitized RGB signals are converted in format from an {R,G,B} representation to {Y,U,V}. Industry-
standard compression algorithms implemented in the DSP are then used to reduce the source data to a
more manageable size, and to generate sequences of I-P-B frames found in MPEG-4 media streams.
2.4. T
RANSMISSION
The MPEG media stream is split into segments, which are then encapsulated into RTP packets according to
the protocol standards set forth in IETF RFC 3016 or RFC 3984 (H.264). These packets are presented to the
Ethernet hardware interface for subsequent transmission on the attached IP network.
2.5. D
ECOMPRESSION
The received packet stream is decompressed and the resulting image is placed into a video frame buffer. At
that instant it will become visible to the receiving viewers.
2.6. D
ISPLAY
F
UNCTION
The display will output imagery from two different sources. If the unit is configured as the sending unit, a
local copy of the captured image (prior to compression, but after capture and conversion to digital format) will
be displayed. If the unit is a receiving unit, the displayed image will be from the remote sender.
2.7. A
UDIO
S
UBSYSTEM
Each Presentation Recorder supports an audio subsystem consisting of an high-quality codec and
associated input/output connectors. The unit has microphone and line-level input signals, and a line-level
output signal. Each line-level connector supports stereo signals. An XLR connector provides for mono
balanced audio input. Audio input via the HDMI connector is not currently supported.
2.8. A
RCHIVE
F
LASH
D
ISK
A flash memory card in the Presentation Recorder is available for recording transmitted sessions. The file
format is standard MPEG-4 Part 10 (H.264, .mp4), which can be played on a variety of desktop client
players, or these same files can be installed on a video-streaming server for on-demand playback over the
Internet. All unit come with 32 GB of storage standard, and an additional 32 GB of storage may be
purchased as an option.
NCast Corporation
Revision 1.1
Page 15
