Don in 30 lines

30-line Television Today

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Contents: [ Digital Scan Converting | Examples of Frame Sequential Colour | Olympic Gymnast | Other Low Definition TV developers ]

Digital Scan Converting
In 1987, after several years of saying that 30-line TV was better than my restored images, I built a digital scan converter to prove it. 
Don's Scan Converter (High to Low Definition) The device (on the left) took 625-line PAL and converted it to a variety of low definition TV standards in monochrome and colour. It was a modular design to allow any format to be tried out - though I built it for 64 line, 32 line and 30-line mono and colour and even 15-line colour (as per Baird's 1928 experiments). Converting down from broadcast format gave me the benefit of having a broadcast quality source (excellent lighting and camera view) with professional action (plenty of movement). (Amateur material usually cannot address both those categories).
  • There is a 'super-resolution' effect as objects move across the 30-line frame.  This gives the effect of having more detail.
  • With a human subject, the brain contributes substantial 'recognition' capability. At 1/900th of original broadcast bandwidth, the recognised content bizarrely surpasses the capabilities of the system.
  • Conversely, with static subjects like landscape and buildings, the image often is totally unrecognisable - even in colour.

Examples of Frame Sequential Colour

Frame Sequential Colour Images (from audio tape)

©D F McLean 1990 from off-air broadcasts
In all instances, the television programme was stored on stereo audio tape - vision and sound taking the left and right channels.  The pictures above show how good low-definition colour can be. I'm sure you can recognise at least one - (Richard Feynman, Suzanne Vega, Terry Wogan). They are single frame-sequential R-G-B frames captured off audio tape on my colour frame store (built in 1978).

Olympic Gymnast on Beam
Whilst frame-sequential colour has a slow update rate and suffers from colour break-up, the straight monochrome image yields excellent quality in movement. This Real Video sequence on the right, though much poorer than the version off audio cassette, gives an idea of why movement is so important. The off-tape original is 30lines 12.5 frames per second.

(The scan converter has an additional facility for manually panning the scanned field within the high-definition field of view to capture the movement)

 Olympic Gymnast

reallogo.gif (1268 bytes)

Click icon or image for Real Video (with audio) extract.

from BBC transmission

Other Current Low Definition TV developers
Check out the NBTVA on my Links page.  

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Main Index, | The World's FIRST TV Recordings, | Early Television History, | The Earliest Recording of Broadcast TV: Silvatone 1933, | The First Recording to be Sold - Major Radiovision 1934, | The "Marcus Games" Discs ]

All material in this page is copyright ©DFMcLean 1998 except where specified.

Last updated by Don McLean on 08 March 2005