Opened 15 years ago

Closed 15 years ago

Last modified 14 years ago

#2087 closed patch (fixed)

Clean up US frequency tables

Reported by: sphery <mtdean@…> Owned by: danielk
Priority: minor Milestone: 0.21
Component: mythtv Version: head
Severity: low Keywords:
Cc: Ticket locked: no


As described in #2060 and the thread at , the NTSC cable frequency tables (including standard, HRC, and IRC) have various discrepancies. The attached patches can be used to correct the discrepancies as described in the comments.

Attachments (1)

mythtv-digital_hrc_irc_finetune.patch (7.8 KB) - added by sphery <mtdean@…> 15 years ago.
Patch for finetuning the digital HRC/IRC frequency tables.

Download all attachments as: .zip

Change History (20)

comment:1 Changed 15 years ago by danielk

Milestone: 0.20
Type: patchtask
Version: head

Changing to a task. The digital tables should be fixed as well and there are no patches for those.

comment:2 Changed 15 years ago by sphery <mtdean@…>

Summary: Clean up NTSC cable frequency tablesClean up US cable frequency tables
Type: taskpatch

Added patches for digital frequency tables. My recommendation is to apply the following patches before 0.20 release (in the order specified):


Doing so will only fix the values that will not work and does not remove any channels (even where they're not defined for the frequency table). Once these patches are applied, milestone can be changed to 0.21.

After 0.20, we can do the more experimental changes, such as:

  • removing channels (i.e. channel 1 in standard and T-band channels in HRC/IRC), if desired
  • finetuning frequencies (i.e. using the 6.0003MHz step for HRC and adjusting IRC by 12.5kHz (or 25kHz for 42, 98, and 99)
  • possibly creating a new frequency table to allow for differentiation between positive and negative offsets in the radionavigation/radiocommunications bands for channels in the standard frequency tables

These patches may require digital users to rescan channels (depending on which frequencies their cable companies use), but likely no more so than [10593] did.

comment:3 Changed 15 years ago by sphery <mtdean@…>

Summary: Clean up US cable frequency tablesClean up US frequency tables

Added one more that should go in before 0.20 ( mythtv-atsc_fix_freqtable.patch ). Currently, in the atsc_vsb8 frequency table, channels 5 and 6 are at the wrong frequencies (75MHz and 81MHz instead of 79MHz and 85MHz) because of a 4MHz jump between channels 4 and 5.

comment:4 Changed 15 years ago by danielk

(In [10644]) Refs #2087. Applies "mythtv-atsc_fix_freqtable.patch" with a copy paste error fix (channels 5 & 6 were called 2 & 3); plus adds some useful whitespace in frequencies.c at frequency discontinuities.

comment:5 Changed 15 years ago by danielk

(In [10645]) Refs #2087. Applies "mythtv-digital_cable-scanfrequencytable_labels.patch" + updates help text to match.

This just changes the human names of the high frequency tables to use "High" as the modifier, instead of trying to express the frequencies scanned via incomplete reference to the corresponding channel numbers. That just caused confusion, and didn't add anything except _maybe_ to the limited number of people who had read way too much cable industry technical literature.

comment:6 Changed 15 years ago by danielk

(In [10646]) Refs #2087. Removes T-band channels from digital HRC & IRC tables. See:

These were harmless, but unneccesary.

comment:7 Changed 15 years ago by danielk

(In [10647]) Refs #2087. Removes T-band channels from analog HRC & IRC tables. See:

These were harmless, but unneccesary.

comment:8 Changed 15 years ago by danielk

(In [10648]) Refs #2087. Removes NTSC Standard Cable Channel 1.

This channel was removed from the broadcast standards in 1945 (on which this portion of the cable channel assignments is based).

According to what I have found via google, it has not been used since the 1970's.

This applies "mythtv-digital_cable-remove_channel_1-before_fix_standard.patch" and "mythtv-ntsc_cable-remove_channel_1.patch"

comment:9 Changed 15 years ago by danielk

(In [10649]) Refs #2087. Fixes T-Band channels for both digital and analog tables.

These channels were off by 1.25 Mhz, the wrong carrier was probably referenced when these were initially created.

Applies "mythtv-digital_cable-fix_t_band-before_fix_standard.patch" and "mythtv-ntsc_cable-fix_t_band.patch"

comment:10 Changed 15 years ago by danielk

(In [10650]) Refs #2087. Re-enumerates the "cable#" internal names and coaleses the 23-69 & 70-94 frequencies into a single entry since they are continuous.

Applies the idea of "mythtv-digital_cable-fix_standard.patch", the exact patch did not apply.

comment:11 Changed 15 years ago by danielk

Milestone: 0.200.21
Severity: mediumlow

I've applied all the major fixes, I'm pushing the fine-tuning of the tables off to 0.21. We also probably want to add some code to fix any fine-tuning the users have already done to match the new fine-tuned table entries.

comment:12 Changed 15 years ago by sphery <mtdean@…>

There were a couple of changes that got lost in the mess of patches. They are fixed by the patches mythtv-20060726-digital_cable.patch and mythtv-20060726update-digital_cable_hrc_irc.patch . (Please don't use mythtv-20060726-digital_cable_hrc_irc.patch--without the word update--it's missing an end frequency change. Sorry.)

comment:13 Changed 15 years ago by danielk

(In [10792]) Refs #2087. Adds back missing channels in standard cable frequency table thanks to report from Harley Peters.

comment:14 Changed 15 years ago by danielk

[10794] applied mythtv-20060726-digital_cable_hrc_irc.patch and mythtv-20060726update-digital_cable_hrc_irc.patch

comment:15 Changed 15 years ago by danielk

(In [11390]) Refs #2087. Finetunes Cable HRC table.

Our HRC table entries are a few kHz off. This corrects for that with a patch from mtdean at thirdcontact com.

Generally the lower channels were within the rounding error of the bttv and ivtv drivers, but the error accumulates so that at 125 it is three bttv/ivtv finetune ticks from the correct value. If you are using HRC and are not finetuning the upper channels this should improve your analog reception a bit. If you were finetuning, you should clear for your HRC channels.

comment:16 Changed 15 years ago by danielk

Resolution: fixed
Status: newclosed

(In [11391]) Fixes #2087. Finetunes Cable IRC frequency table.

Like the HRC table our IRC table was a little off. Except for three channels this was within rounding error for ivtv/bttv drivers, the three channels that were off by more, were off by only about one finetuning tick in these drivers. This should make no real difference in tuning for either of the most popular analog cards, but simply aligns the table with published standards.

Changed 15 years ago by sphery <mtdean@…>

Patch for finetuning the digital HRC/IRC frequency tables.

comment:17 Changed 15 years ago by sphery <mtdean@…>

Resolution: fixed
Status: closedreopened

The attached patch fine tunes the digital HRC and IRC frequency tables. The code changes compile fine and I've re-checked the frequencies multiple times, so I'm pretty certain everything is correct in the patch. However, I don't have cable, so it's untested.

I couldn't find the macros used for creating DVB frequency tables to see if one was what I needed, so I just modified the one that was used for US digital cable to allow specifying the bandwidth (instead of using a value of 6MHz for all frequency tables). If there is other code I could have re-used, instead, please let me know.

The patch breaks creation of the frequency tables into two sections of code rather than using a loop to create HRC and IRC as before. While HRC and IRC were very similar (allowing a simple mathematical calculation of frequencies) when using "approximate" values, using exact values makes the calculation far more complex (and much less maintainable code). To get an idea of what it looks like, see .

comment:18 Changed 15 years ago by danielk

Resolution: fixed
Status: reopenedclosed

(In [11492]) Fixes #2087. Finetunes digital IRC and HRC tables.

In order to use these new finetuned frequencies you must delete all channels on the source and rescan. In practice the old frequencies were not far off enough to justify doing this.

comment:19 Changed 14 years ago by Jarod Wilson

(In [13219]) - Backport changesets [11390], [11391] and [11492] to 0.20-fixes

  • Refs #2087
  • Fixes up US cable irc and hrc frequency tables
  • Resolves digital channel scanning failures (at least for me, w/Comcast, us-cable-irc)
  • Possibly related to #2636

(11390, 11391, 11492)

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