Opened 13 years ago

Closed 13 years ago

Last modified 13 years ago

#2060 closed defect (fixed)

US cable frequency tables incorrect

Reported by: mrussotto@… Owned by: danielk
Priority: minor Milestone: 0.20
Component: mythtv Version: head
Severity: medium Keywords:
Cc: Ticket locked: no

Description

The cable and cable 78+ frequency tables for US Cable are incorrect, which results in channel numbers which don't match those on my digital TV. Cable channels aren't contiguous, instead they match broadcast from 2-13, 14-22 are tucked between 6 and 7, then 23-94, then 95-99 are between 6 and 14, and 100 starts where 94 left off. Also channel 78 is at 549Mhz, not 537Mhz (channel 76). See for example http://www.atxnetworks.com/qrf/catvfrq1.htm , although this gives the video carrier rather than the center freqeuncy.

For the 78+ table:

Current:

        FREQ(modStr[i], "cablehigh0", desc[i], "Channel %1", 
              78, 537000000,1005000000, mod[i]); 

Correct (I think):

        FREQ(modStr[i], "cablehigh0", desc[i], "Channel %1", 
              78, 549000000,645000000, mod[i]); 
        FREQ(modStr[i], "cablehigh1", desc[i], "Channel %1", 
              100, 651000000,999000000, mod[i]); 

Possibly this should be a different ticket, but the sub-channel number is incorrect also; digital sub-channels are numbered from 1 and mythtv numbers them from zero.

Change History (6)

comment:1 Changed 13 years ago by danielk

Resolution: invalid
Status: newclosed

Russotto, the table you reference looks like it is either a HRC or IRC table. (I didn't bother with the visual to centre frequency conversion, but probably only one of those will work for you so just try both.)

comment:2 Changed 13 years ago by mrussotto@…

Resolution: invalid
Status: closedreopened

Err, no, definitely not. The HRC and IRC channels are offset from the normal values; the frequencies used by MythTV for regular cable are completely incorrect; because they cover the right range, you get all the channels, but with the wrong channel numbers.

The chart I pointed to give the standard EIA-542 frequencies; add 1.75 to the video carrier to get the center. You can also look at the frequencies used by the linuxtv project in their dvb-apps application

linuxtv-dvb-apps-1.1.1/util/scan/atsc/us-Cable-Standard-center-frequencies-QAM256

comment:3 Changed 13 years ago by danielk

Resolution: wontfix
Status: reopenedclosed

comment:4 Changed 13 years ago by danielk

Milestone: 0.20
Resolution: wontfix
Status: closedreopened
Version: head

Reopening, this is not just a numbering problem for cable channels < 500 Mhz.

comment:5 Changed 13 years ago by danielk

Resolution: fixed
Status: reopenedclosed

(In [10593]) Fixes #2060. Fixes some of the frequencies scanned by MythTV for QAM in the US.

The upper frequencies had the wrong enumaration and some of the lower channels had the wrong frequency. Most systems still use the lower channels for analog channels, so in practice few people will see additional channels, but...

comment:6 Changed 13 years ago by danielk

I mostly used the frequencies in frequencies.c to build the table.

The T-# channels did disagree with the ones in the URL you referenced. One of them has to be wrong...

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