I guess I was confusing it with LDPC erasure codes where you already know which blocks or symbols are missing. That becomes much simpler. At my last job I implemented those in software for real time Internet video streaming. It would only take 2-5% of percent of a 3 Ghz PC to error correct a 3 mbps stream, leaving plenty of room to spare for software video decoding. But I was xor'ing entire blocks together, with a tiny bit of assembler code added for optimization. And I didn't have to try to figure out which blocks were missing or erroneous, just calculate the values of the blocks known to have not arrived in time.
- Tom Allen Le Roy Limberg wrote:
Tom Barry queiried:Except for memory for buffering I thought LDPC took very little effort,linear time and just a bunch of xor's. What is the bottleneck? The decoder end is the concern. In 1958, Robert Gallager, then a Ph.D. student at the Massachusetts Institute of Technology (MIT), created a class of codes that, like Hamming's codes, add redundant bits that permit decoders to do even-odd checks to guess which bits of the original message have been corrupted by noise. As with turbo codes, Gallager's LDPC codes use cross talk between decoders to gradually establish confidence about the likely bits of the original message. However, in contrast to turbo codes, which use just two decoders, LDPC codes use a separate decoder for each bit of the message, creating a giant rumor mill. That requires thousands, or even tens of thousands, of decoders. Al Limberg----------------------------------------------------------------------You can UNSUBSCRIBE from the OpenDTV list in two ways:- Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.
-- Tom Barry trbarry@xxxxxxxxxxx Find my resume and video filters at www.trbarry.com ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways:- Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.
