Mark Atherton, ZL3JVX, New Zealand DigiLiteZL Digital Video TV Modulator project

Mark Atherton, ZL3JVX, New Zealand

DigiLiteZL

Digital Video TV

Modulator project


Why ?• 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


How ?• 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’


Status• 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


What is Digital TV ?• 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


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


Video processing• 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)


Audio processing• 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)


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.


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”


DigiLite (UK)• 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)


DigiLiteZL - 1• 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


DigiLiteZL - 2• Where to go from here

– PC-less standalone repeater– Video source from modified consumer DVR– User interface using soft processor– UDP over Ethernet

• Needs 100 base T


DigiLiteZL - 3

Documents

Mark Atherton, ZL3JVX, New Zealand DigiLiteZL Digital Video TV Modulator project