I see that I may need to clarify this subject and place a link from WIKI.
Error correction is a technology that is used by the ATSC tuner to make sure that any data that is missing can be corrected. For instance, sometimes interference or a poor-quality signal will cause the loss of data information that the ATSC tuner receives. With error correction, the tuner has the ability to perform a number of checks and repair data so that a signal can be viewed on a TV set.
There is a subsection in the ATSC standard (ATSC-E) that allows broadcasters to add extra (and variable types) of error correction to their broadcast streams.
This error correction service is not mandatory in the US, nor is it mandatory in Canada.
It is not known how many HDTV receivers support this error correction standard.
For the transmission of HDTV at 720 or 1080, an extra 1% to 3% added error correction codes will help reduce some of ATSC's poorer performance with weak signals under adverse multipath conditions.
One can assume that if anything is not mandatory, neither the tuner makers nor the brodcasters are likely to implement it. On the CECB side it should be easier to figure out since one could look up the specs of the tuner chips used. When a broadcaster can't even get PSIP and other things right yet, expecting them to implement something that is not even required is too much of an expectation.
Mark posted this over in the DMA forum for Baltimore.
We did a test with ATSC-E about 1.5 years ago, with a 54.2 subchannel. It helped with trying to pick up a signal in a bad multipath area. It used a lot of bits for error correction that would otherwise go toward getting a nice HD picture. I'm pretty sure that no one in the US is using this.
I wonder why they didnt make that mandatory originally ? With digital transmission, thats exactly what is needed. Just think back when modems didnt have error correction, heh.
I don't know if you are thinking that ATSC does not require error correction or not but this is not the same as modems not having error correction since the ATSC standard for digital transmissions does mandate error correction.
What is being discussed here is the "extra" error correction which is optional in ATSC-E. If digital transmissions did not have error correction at all then you would have to have a 100% signal quality for undisturbed viewing.
About 1/3 of the data in ATSC transmissions is forward error correction (FEC) data. ATSC has an FEC of 2/3 which means only about two-thirds of the data transmitted is the main signal and 1/3 is used for error correction.