DigiLiteZL
Digital Video TV
Modulator project
Mark Atherton, ZL3JVX, New
Zealand
Why ?
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Amateur TV may need to go digital by 2012
Educational platform
Completely open source project
General purpose Digital TV development platform
Possibility of building a PC-less DATV repeater
Mark Atherton, ZL3JVX, New
Zealand
How ?
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Building on Digilite (UK) project
FPGA rather than dsPIC based
DigiLite compatible
Team effort
First attempt managing an open source project
FPGA designer works for Google
RF guy works for Tait
As Charles says ‘you get to order the pizza and sweep the floor’
Mark Atherton, ZL3JVX, New
Zealand
Status
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2 units built and completely working based on DigiLite (UK)
1 partial kit sent to FPGA designer in US
BOM up to date
Schematic marked up
Verilog of modulator nearly ready for simulation
Web site up
– http://tinyurl.com/423ppt3
– 1100+ hits
– Want comments about alternate configurations
– Other possible uses
Mark Atherton, ZL3JVX, New
Zealand
What is Digital TV ?
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A mix of video, audio and data
Majority of Video coding uses MPEG2
Majority of Audio coding uses MPEG2 or Dolby Digital
Different modulation for Terrestrial, Cable and Satellite
US and Europe use different terrestrial modulation
Satellite modulation mainly used by Hams, even for terrestrial
Broadcast Digital Video is just a continuous stream of data
Data rate is in the region of 4-45Mb/s
Modulator depends on the medium
Mark Atherton, ZL3JVX, New
Zealand
What does a broadcast stream contain ?
• One or more program(s)
• Each program generally contains one or more audio channel
– “Radio” channels are audio only
• Each program generally contains zero or more video channels
• System Information (SI) tables that provide context
• Possibly also Electronic Programme Guide (EPG) tables
Mark Atherton, ZL3JVX, New
Zealand
Video processing
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Acquire analogue video, convert to baseband digital, ~270Mb/s
Compress using MPEG2 encoder, 2-10Mb/s
Wrap in packets of 188 bytes, add packet identifier (VPID)
Now called a Video Packetized Elementary Stream (VPES)
Mark Atherton, ZL3JVX, New
Zealand
Audio processing
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Acquire analogue audio, convert to baseband digital, ~1.5Mb/s
Compress, using audio encoder, around 200kb/s
Wrap in packets of 188 bytes, add packet identifier (APID)
Now called the Audio Packetized Elementary Stream (APES)
Mark Atherton, ZL3JVX, New
Zealand
System Information
• 188 byte metadata (tables) giving context to the complete stream
• Program Association Table (PAT)
– Always located at PID 0
– Number of programs present in the stream, and where
– List of PMTs
• Program Map Table (PMT)
– Binding audio and video into programs
• Electronic Programme Guides
– What’s-on-next etc.
Mark Atherton, ZL3JVX, New
Zealand
System Multiplex
• A mix of video, audio and SI tables
• Padded to required data rate using null packets
• Resulting data is called a “Transport Stream”
Mark Atherton, ZL3JVX, New
Zealand
DigiLite (UK)
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Low cost satellite modulator project from the UK
Requires closed source pre-processed TS
Closed source dsPIC
External LO
USB 2.0 data interface
Digital power from PC (via USB)
Mark Atherton, ZL3JVX, New
Zealand
DigiLiteZL - 1
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On board, or external LO
Direct interface to DE0-nano FPGA board
Plug in baseband IQ filters
USB 2.0 data interface
Digital power from PC (via USB)
PICKIT2 programming header for dsPIC
Single ext 5V analog supply
Low cost Digital TV development platform
(very) extensible, replaces dsPIC with FPGA
Many other possible data sources
– Ethernet
– ASI
Mark Atherton, ZL3JVX, New
Zealand
DigiLiteZL - 2
• Where to go from here
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PC-less standalone repeater
Video source from modified consumer DVR
User interface using soft processor
UDP over Ethernet
• Needs 100 base T
Mark Atherton, ZL3JVX, New
Zealand
DigiLiteZL - 3
Mark Atherton, ZL3JVX, New
Zealand