[mythtv-users] Cannot change channel and "low FPS" problems

Bruce Markey bjm at lvcm.com
Thu May 5 19:38:11 UTC 2005


Rickard Borgmäster wrote:
> Hello,
> 
> Could someone please explan what is what of:
> * Channel ID

The database unique row number used to find that specific
set of information.

> * Channel number

The number on the dial (back when TV's had dials) that you
twist to in order to receive that channel.

> * Channel callsign

The short set of letters to identify the TV station that is
normally broadcast over this channel.

* Channel name

A longer text name to identify the TV station that is normally
broadcast over this channel.

First, a "channel" and a "station" are not the same thing. A
station is in a building with employees with lots of wire and
equipment and usually has an antenna on top or on a nearby hill.
A channel is a frequency or identifier that a TV set uses to
select a signal on the wire from an antenna or cable. The same
station may be available on two or more channels or from two
or more video sources (over the air, cable, satellite, digital).
The same channel (frequency) in another location may carry a
different station's broadcasts.

mysql> select chanid, channum, freqid, sourceid, callsign, name from channel
    -> where callsign = 'CNN' or callsign = 'HBO' or callsign = 'KVBC'
    -> order by callsign;
+--------+---------+--------+----------+----------+--------------------+
| chanid | channum | freqid | sourceid | callsign | name               |
+--------+---------+--------+----------+----------+--------------------+
|   1020 | 20      | 20     |        1 | CNN      | Cable News Network |
|   2210 | 210     | 210    |        2 | HBO      | Home Box Office    |
|   1003 | 3       | 3      |        1 | KVBC     | KVBC (NBC)         |
|   2003 | 3       | 3      |        2 | KVBC     | KVBC (NBC)         |
|   2123 | 123     | 123    |        2 | KVBC     | KVBC (NBC)         |
+--------+---------+--------+----------+----------+--------------------+
4 rows in set (0.01 sec)

Chanid distinguishes that 1003 and 2003 are the information for source
1 and 2 even though they are the same station on the same channel.

Channum 123 is a different channel for KVBC and needs a different
frequency to get the programming from the same station that is also
on channel 3.

Freqids for source one are sent to the tuner for the coax input.
Source 2 is a digital cable box connected to s-video and the freqid
is sent to an external script.

Sourceid 1 is analog coax cable. 2 is from a digital settop box.

The callsigns can be used in small spaces in the UI to identify
the station such as the left column of the EPG or the middle column
for Upcoming Recordings. However, it is also used by the scheduler
for 'channel matching'. If I set a Channel record rule for "The
Apprentice" (NBC) on 123, the scheduler sees that this is on KVBC
and it could use chanid 1003, 2003, or 2123 to record this. More
info on how and why it chooses which one to use can be found at:

  http://www.mythtv.org/docs/mythtv-HOWTO-11.html#ss11.7

The channel name has no function other than for display in the
UI where there is room for a full station name like the information
area at the bottom of the Set Priorities page.

--  bjm


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