[opendtv] Re: ATSC-Mobile

  • From: Tom Barry <trbarry@xxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Mon, 12 Feb 2007 23:13:08 -0500

Correction - meant "very little effort".

- Tom

Tom Barry wrote:
Except for memory for buffering I thought LDPC took very effort, linear time and just a bunch of xor's. What is the bottleneck?

BTW, I just noticed Raptor codes (used in DVB?) on Wikipedia the other day. These seem interesting also.

In computer science, raptor codes are the first known class of fountain codes with linear time encoding and decoding. They were introduced by Amin Shokrollahi in 2004.


- Tom

PS - My brain-dead spell checker didn't know "raptor". Must not have seen the movie.

Allen Le Roy Limberg wrote:

Smells like a low density parity check system proposal might be in the works. The problem with current LPDC technology is that the receiver gets pretty complicated. A-VSB employs turbo coding, which has the advantage that receiver costs can be better kept in hand. Nobody in DTV seems to be noticing that NASA is using Golay coding with (255, 223) R-S coding to get very close to Shannon limits. New ways to perform list decoding allows many, many more byte errors than 16 per codeword to be corrected by the R-S forward-error correction coding without hardware and software costs getting completely out of hand. Cost of receivers that approach Shannon limits will probably be a major factor in deciding on a mobile transmission scheme, IMHO. Al Limberg

Tom Barry                       trbarry@xxxxxxxxxxx     
Find my resume and video filters at www.trbarry.com

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