Embedded Video Processing and Radio Unit
The embedded video processing and radio unit (VPRU) is a small, high performance single board computer for capturing and transmission of high definition video and for providing a simple TM/TC interface for the system it is built into.
- Capture high quality video in 640x360 and 1280x720 pixels, 25 fps, progressive scan
- Perform some basic compression of the video stream in real time
- Provide a TM/TC interface to other processing units
- Interleave telemetry from other processing units and the video stream and transmit it over a radio link
- Receive telecommands via the radio and forward them to the other processing units
Nice to have requirements:
- Pan, tilt, and zoom
- Transponder functionality in the radio unit for ranging
The camera can be either CCD or CMOS. It sends RGB or YCbCr data to the video engine from which it also receives control signals.
Video engine & Cam control
Compresses and encodes the video data from the camera in real time. The video engine has three major operating modes:
- High-rate TM: The high quality video is forwarded in real-time at its original size to the TM encoder. This mode is used when there is sufficient radio bandwidth for high-rate transmission.
- Low-rate TM: The high quality video is stored in the Storage at its original size for later retrieval and a reduced-size preview is forwarded in real-time to the TM encoder. This mode is used when the radio link can only provide sufficient bandwidth for low rate transmissions.
- Retrieve: This mode is used when the capturing was done using the Low-rate TM mode and the high quality & size video needs to be downloaded in non-real time.
The storage is used for storing video for later retrieval when only low-rate TM transmission is possible.
The telemetry encoder receives video data stream and telemetry data from the video engine and interleaves them with telemetry from other sources. The interleaved telemetry stream is sent to the radio transmitter (TX).
The TC decoder receiver telecommands from the receiver unit (RX) and decodes them. Camera and video related commands are sent to the video engine and cam control, other TCs are sent to the Auxiliary Units.
RX and TX
These are the radio units: Transmitter (TX) and Receiver (RX). The transmitter converts a digital data stream fromt he TM encoder into a radio frequency signal. On the other hand, the receiver converts a radio frequency signal into a digital data stream and sends it to the TC decoder.
This has been added to allow using the same antenna for both transmission and reception.
This has been included to allow interaction with other on-board units so that they can share the RX/TX connection.
The VPRU is going to be developed in three incremental iterations resulting in three prototypes:
- First Prototype
- This prototype will focus on the video processing functionality and the TM/TC interface. For the radio part, a simple Wi-Fi interface will be used allowing laptops and handheld devices to act as hosts.
- Second Prototype
- This prototype will focus on the radio unit and implement the transponder functionality.
- Third prototype (TBC)
- This prototype will focus on adding the pan tilt and zoom functionalities and will be likely to replace the camera unit from the first and second prototypes.
Two processors from Texas Instruments are evaluated:
Both are based on the DaVinci™ technology and contain hardware accelerators for video processing (both front end and backend). The OMAP2530 also contains a C64x+ DSP using which Software defined radio functionality could be implemented.
While these may not provide the best solution, they are relatively easy and cheap to get started with, because development environments are available in the form of the Beagle Board, the Leopard Board, and the Gumstix series.
To begin with, following borads have been acquired:
- Leopard Board that comes with a VGA camera and a 5 Mpix camera.
- Gumstix Overo Fire with the Summit expansion board.