Frequency scan

In order to be able receive a particular signal with your TV tuner device you will need to tune/set it to the correct radio frequency used by that source transmission. Therefore, you (or, at least, the viewing application you are using) will first want to know which frequencies are used for transmission and, thereby, may be tunable by your receiver at your residing location. Frequency scanning utilities, listed below, perform such signal detection and, generally, provide a list of the frequencies upon which content is discovered, with which higher level applications can then in turn use for tuning purposes.

Note: Historically, the set of frequencies used under the older analogue systems have differed from one another, meaning that the particular frequencies used across North America, Europe, Asia, etc., etc., will differ depending upon the transmission standard adopted within each nation. When countries began to make the transition to digital TV systems, most have opted to continue to use their old channel frequency schemes so as to make the switch from analog to digital systems as seamless as possible for the end user.

Frequency Scanning Utilities

Analog

• scantv (part of xawtv package, both branches)
• apps with built in scanning ... tvtime, xawtv/motv (which call upon scantv), kdetv ...

Digital

On Digital TV, the scanning process consists on tuning into some physical channel/transponder frequencies and parsing the MPEG Transport Stream, in order to identify the services and the corresponding audio, video, teletext and data streams. The service is also known Virtual Channel.

There are two types of scanning applications: the ones that rely on frequency channel files and the ones that tries hard to identify the existing channels, based on the knowledge of the Country.

Scan apps based on a channel file

Those applications are faster to identify the channels, but they are unable to find any channel outside the channel table.

For them to work, an initial file is needed. Those files are provided at dtv-scan-tables repository, using dvbv5 file format.

Most common applications used for channel scan:

• LinuxTV dvbv5-scan, part of DVBv5_Tools package.
• alexplore (part of the v4 xawtv package).
• scan/"(dvb)scan", part of the unmantained LinuxTV dvb-apps.
• scan-s2 [1]
• "(dvb)scan", a utility included within the LinuxTV dvb-apps package.
• several apps also have their built in scanning ... kaffeine, MythTV, Me TV

Scan apps that don't require an initial channel file

Scan applications that don't need a channel file have internally a table that allows them to construct internally a table with possible frequencies and tuning parameters to seek. As the number of possible channels/tuning parameters are a way higher than the ones defined on a channel table, the scanning process will take several minutes (up to an hour, if the card doesn't support autodetection for some DVB properties).

Applications using this approach:

• w_scan

Comparison of DVB frequency scanning commandline utilities

Note: The differences between scan and dvbscan should be added to this wiki article. The information for dvbscan is still to be completed - please help.

The following table lists the main features of several of the popularly used command line scanners. For specific information on a particular utility's usage, have a look at its specific wiki article.

feature \ scanner	scan	dvbscan	w_scan	scan-s2	dvbv5-scan
download (upstream version)	linuxtv.org/hg/dvb-apps	linuxtv.org/hg/dvb-apps	wirbel.htpc-forum.de/w_scan/index.html	mercurial.intuxication.org/hg/scan-s2	git.linuxtv.org/v4l-utils.git
last stable	linuxtv-dvb-apps-1.1.1	linuxtv-dvb-apps-1.1.1	none / use latest version	?	v4l-utils-1.4.0
comments	linuxtv.org unmaintained DVB-S2 and DVB-T2 support missing	linuxtv.org unmaintained DVB-S2 and DVB-T2 support missing			linuxtv.org maintained
DVB API needs	DVB API version 3.2 or higher	DVB API version 3.2 or higher	DVB API version 3.2 or higher compiling needs DVB API version 5.0 or higher	DVB API version 5.0 or higher last update 02/2009	DVB API version 3.2 or higher
supported DTV types	DVB-S, DVB-C (Annex A only - mainly Europe), DVB-T, ATSC (VSB and QAM)	DVB-S, DVB-C (Annex A only - mainly Europe), DVB-T, ATSC (VSB and QAM)	DVB-S, DVB-S2, DVB-C (Annex A only - mainly Europe), DVB-T, DVB/T2, ATSC (VSB and QAM), DMB-TH (China)	DVB-S, DVB-S2, DVB-C (Annex A only - mainly Europe), DVB-T, ATSC (VSB and QAM)	DVB-S, DVB-S2, DVB-C (Annex A and C - worldwide), DVB-T, DVB-T2, ATSC (VSB and QAM), ISDB-T and more
initial scan file required (matching to your satellite or local aerial/cable network)	yes	yes	not required	yes NOTE: slightly different file format from scan because of additional DVB-S2 support.	yes (uses libdvbv5 file format by default, but dvb-apps and s2-scan file formats are accepted too)
can generate initial scan file	no	no	yes	no	no
can generate channels.conf for zap/xine/mplayer/vlc	yes (default)	yes (default)	yes	yes	yes
can generate channels.conf for VDR	yes, but hopeless outdated (vdr-1.3 only)	yes, but hopeless outdated (vdr-1.3 only)	yes (default)	yes (default)	yes (after version 1.4.0)
can generate channels.dvb for kaffeine	no	no	yes	no	no

External Links

Analog

Digital For some other general sources (which may or may not be that useful) for finding local channel frequency lists, see:

• http://www.vdr-wiki.de/wiki/index.php/Kanal_DVB-T - DVB-T channels in Europe
• http://www.wohnort.demon.co.uk/DAB/
• http://www.digitalspy.co.uk/terrestrial/tuning/