Department of Electrical and Systems

Engineering

ABSTRACT

Television has been an excellent medium for entertainment and information ever since the invention of the electron scanning tube in 1923 by Vladimir Kosma Zworykin, who is considered the father of the modern television. Unfortunately, people sharing a television are forced to watch one channel at a time or use a different television if they want to watch different programs. As a result, there are often arguments about which channel to watch. There is currently no system that allows viewers in the same room to view different channels without the use of multiple televisions. Present day systems such as picture-in-picture (PIP) are largely ineffective as they only use a small fraction of the screen area for the secondary channel, and there is no way of hearing the audio from that channel.

The goal of this project was to design a system that solves these problems. The DoubleVision Television (DVTV) system comprises of a NTSC processing unit that allows two groups of viewers to simultaneously watch different channels on the same television. Two groups of viewers can use shutter glasses with built-in polarization properties to differentiate and watch two different channels. The two sound signals from the two different channels are separated and transmitted to the appropriate user via a wireless headphone system.

A mixer box [DVTV Box] was built to interlace two separate channels that can be displayed on any standard CRT TV. First, two analog NTSC signals of the viewers’ choice are extracted from the multi-channel frequency band coming from the cable provider or any video source such as VCR or DVD. The sound signals are simultaneously separated and sent to the RF transmitter which transmits the two separate sounds to two separate headphones. Then, the two video signals are synchronized using a time base correction unit. These two separate synchronized NTSC channels are interlaced by a video multiplexer circuit. The timing signal is extracted and used to control this video multiplexer. The output of the multiplexer becomes a single field-sequential NTSC signal with the odd and even fields representing channel A and channel B respectively. The same timing signal is used to control the shutter glasses, which turn ON and OFF at the right time to give two viewers two completely different channels.

PRESENTERS Nii Ayite Ayite EE ’05

Zereyacob Girma EE’05Aung Naing EE ’05

GROUP 9

ADVISORS Dr. Kostas Daniilidis

Dr. Nader Enghetta

SPECIAL THANKS TOMr. Sid Deliwala

Dr. Shih-Schon Lin

DEMO TIMESThursday, April 21st, 2005

11:30AM, 1:00PM, 1:30PM and 3:00PM

DoubleVision Television

1. NTSC SIGNAL

The NTSC standard for television defines a composite video signal with a refresh rate of 59.94 fields (half-frame) per second (approximately 60Hz). Each frame contains 525 lines stacked horizontally. A field is a set of even lines, or odd lines. The odd and even fields are displayed sequentially about every 1/60 of a second, thus interlacing the full frame.

4.  TIMING EXTRACTION

The vertical sync information is extracted from the tuned, synchronized channels and passed on to the control unit. The control unit uses the vertical sync to generate sync signals to control the video multiplexer unit as well as the switching of the shutter glasses.

2. CHANNEL EXTRACTION

Incoming NTSC signal (from cable provider, stored media or antenna) is split into two. From each of these signal streams, a desired channel is extracted using a TV tuner (TUN-181). The sound signals are simultaneously separated and sent to the Dual Channel RF Sound transmitter.

6. DISPLAY

The single stream of interlaced fields, which is in NTSC format, is fed into a standard CRT TV. Two complementary sync signals generated by the control unit trigger the glasses ON and OFF at the appropriate moment.

5. VIDEO MULTIPLEXING

The two synchronized channels are passed into the video multiplexing stage. Using the sync signal from the control unit, the two channels are interlaced. The output of the multiplexer becomes a single field-sequential NTSC signal with the odd and even fields representing channel A and channel B respectively. The output retains the NTSC signal structure.

3. TIME BASE CORRECTION

The two TV signals coming out of the TV tuners are out of phase. These signals are synchronized by a time base correction unit. As a result, both of the desired channels have identical vertical sync signals.

9. RESULTS AND CONCLUSIONS

• Two separate channels can be successfully watched by two groups of viewers.• This DVTV box can be used with any NTSC CRT TV.• Whilst each viewer is watching a 30Hz channel, the loss in quality due to the slower refresh rate is minimally noticeable to the average viewer. In other words, while there is a drop in quality in comparison to a regular TV, the viewing condition is more than satisfactory.• The use of 120Hz television will improve quality giving each viewer 60Hz.• TV screens with better response times will result in the optimal quality.• With the use of 120Hz TVs, the system could potentially be extended to four channels with 30Hz for each channel.• The DVTV box can be manufactured cost-effectively.• Potential applications include home theater, cinema, airplane and video gaming.

GROUP 9

7. SHUTTER GLASSES

The operation of the shutter glasses is such that if no electric field is applied, all light can pass through (ON) and if electric field is applied, all light is blocked (OFF). The light coming out of a normal CRT TV is unpolarized and hence suitable for the operation of the shutter glasses.

GROUP 9

8. CIRCUIT PICTURE