[opendtv] Re: Analog v Digital TV
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Tue, 16 Jan 2007 10:28:41 -0500
At 10:26 AM -0500 1/15/07, Manfredi, Albert E wrote:
I never said the MPEG process introiduces redundancy. Just try to follow
the discusasion, please.
I said the MPEG compression deliberately removes redundancy. That's how
it works. But then the digital transmission system reintroduces
redundancy in the bit stream, in the form of convolutional and block
forward error correction.
Get it? No reason to go on about how MPEG works.
Well actually I was responding to the following statement:
Albert Manfredi wrote:
Agreed, Tom. I was taking issue with your "no extra info is sent."
You send redundant info, so that even though MPEG encoding deleted much
of this redundancy info from the image itself, your FEC schemes put it
back in.
Perhaps I did misinterpret what you wrote, but your statement was
highly misleading.
You challenged Tom on the notion that no extra information is sent.
He is absolutely correct.
The FEC bits have absolutely nothing to do with the image bits,
except that they can make it possible to recover the image bits when
some of the data packets are lost or corrupted. The redundancy you
are talking about is error correction bits that protect the payload.
Your statement made it sound like there is redundancy in the image
bits - i.e. the FEC bits put back what MPEG took out.
Regards
Craig
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