Thursday, September 05, 2013

Technologies that made the difference in Television

Will Strauss (writing for Broadcast Magazine) asked me for a couple of ideas for an article he was putting together; you can read it here. My Engineer's Bench collaborator Hugh Waters got in with SMPTE timecode.

The original ideas I sent to him were;

  1. The Mostek MK4096 Dynamic RAM chip (and subsequent MK4196 16k DRAM) was the enabling technology that allowed construction of all early digital video devices in the seventies; TBCs, Framestore Synchronisers and Digital Video Effects (ADO, Quantel 5000, Squeeze-Zoom etc) - being dynamic memory these chips required constant refreshing but the nature of video is that the store is constantly being read to make the next line or frame of video. The chips were fast enough that once multiplexed in banks of (typically eight) video pixels at around 75nS clock could be stored. Without DRAM there would have been no picture-in-picture, no timebase correction, no standards conversion, no digital video effects and no digiscan telecines.
  2. The Discrete Cosine Transform - as a mathematical technique for transforming pixels into frequency distributions the DCT doesn't actually provide any reduction in data for digital TV signals but it does then allow all manner of compression to take place. MPEG2 in the nineties allowed DVD, Transmission servers and DVB-T and DVB-S powering the first wave of standard-definition digital television. In the noughties MPEG4 and later variants (H.264, AVC etc) allowed HD pictures to be compressed to data rates unthought-of previously. Most contemporary video compression starts with the DCT.
  3. Pixel and even frame-free video(!) - this will be the enabling technology of the next decade that will usher in ultra-high-definition TV. Prof Phil Willis of Bath University is pioneering work that will make video a descriptive object technology rather than pixels, lines and frames. Once divorced from set resolutions and framerates it will be up to the display device to render the vectors, contours and shaders at whatever resolution and framerate the device supports.

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