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**Command line dvb-t by example**

I have two budget dvb-t pci cards in a linux box that I use for saving dvb TV programs<sup>//1//</sup> and, since I am a minimalist, sometimes viewing in real time using xine. In this brief tutorial I will explain how to access DVB broadcasts on the command line and introduce a bare bones example script that will tune a channel, encode a broadcast on the fly and save it to disk.

You might ask why in the age of Myth TV would I bother with DVB on the command line to which I would answer that I'm happy enough to be able to open up a terminal (locally or remotely), type in a command, respond to a couple prompts, and schedule a show to be saved for later viewing. I don't need much more than that.

----

If you want to try any of this on your own machine you will need to install /dvb-apps/. If a package is not available for your distro or if you want the latest version go to [[http://linuxtv.org/wiki/index.php/LinuxTV_dvb-apps]] to get themost recent tarball and roll your own. It is a trivial compile with no dependencies or config file. Just run //make// then //make install// for instant gratification or build your own package. If you prefer, you can run most of the utilities straight from the build directory.

Note that some distros package //dvb-apps// as dvb-utils and that there is another bundle of dvb related utilities named DVBapps. If you have installed or built the correct //dvb-apps//, in addition to some include files, libraries and frequency listings you should have installed the following command line utilities

<code>
rick[~]$ ls saves/build/usr/local/bin/
atsc_epg         azap  dib3000-watch  dvbdate  dvbscan     femon  gotox  scan  tzap
av7110_loadkeys  czap  dst_test       dvbnet   dvbtraffic  gnutv  lsdvb  szap  zap
</code>

I will only discuss the use of //scan// and //tzap// in this tutorial. 

In order to tune a channel with //tzap// or indeed other applications including //mplayer// and //xine// you will first need a //channels.conf// file which is created using //scan// and a file containing initial tuning data for at least one transponder/channel for your area. //Dvb-apps// provides this data for the TV transponders in my area (on Mt. Dandenong) in the file ///usr/local/share/dvb/dvb-t/au-Melbourne//.

<code>
rick[~]$ cat /usr/local/share/dvb/dvb-t/au-Melbourne
# Australia / Melbourne (Mt Dandenong transmitters)
# T freq bw fec_hi fec_lo mod transmission-mode guard-interval hierarchy
# ABC
T 226500000 7MHz 3/4 NONE QAM64 8k 1/16 NONE
# Seven
T 177500000 7MHz 3/4 NONE QAM64 8k 1/16 NONE
# Nine
T 191625000 7MHz 3/4 NONE QAM64 8k 1/16 NONE
# Ten
T 219500000 7MHz 3/4 NONE QAM64 8k 1/16 NONE
# SBS
T 536625000 7MHz 2/3 NONE QAM64 8k 1/8 NONE
</code>

To create my //channels.conf// I run scan with the path to //au-Melbourne// and redirect stdout to a file.

<code>
rick[~]$ scan /usr/local/share/dvb/dvb-t/au-Melbourne > channels.conf
</code>

The complete //channels.config// looks like this:

<code>
ABC News 24:226500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:2314:0:560
ABC1:226500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:561
ABC2 / ABC4:226500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:2307:2308:562
ABC1:226500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:563
ABC3:226500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:2311:2312:564
ABC Dig Music:226500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:0:2317:566
ABC Jazz:226500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:0:2318:567
7 Digital:177500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:769:770:1328
7 Digital 1:177500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:769:770:1329
7TWO:177500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:801:802:1330
7mate:177500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:817:0:1331
7 Digital:177500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:769:770:1332
TV4ME:177500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:881:882:1335
Nine Digital:191625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:519:720:1072
GEM:191625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:0:1073
GO!:191625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_3_4:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:517:700:1074
ONE:219500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:514:0:1585
TEN Digital:219500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:512:650:1589
ONE:219500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:514:0:1591
ELEVEN:219500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_16:HIERARCHY_NONE:516:681:1592
SBS ONE:536625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_2_3:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:161:81:785
SBS TWO:536625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_2_3:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:162:83:786
SBS 3:536625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_2_3:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:161:81:787
SBS 4:536625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_2_3:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:161:81:788
SBS HD:536625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_2_3:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:102:103:789
SBS Radio 1:536625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_2_3:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:0:201:798
SBS Radio 2:536625000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_2_3:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE:0:202:799
</code>

Once the //channels.conf// file has been created you can put it in //~/.mplayer// or //~/.xine// if you want to use either of those programs to watch digital TV. I also save a copy as ///etc/channels.conf//to be accessed by the script I use for saving shows to disk.

Note that I have also successfully used this //channels.conf// on a budget WinFast dvb-s (satelite) card connected to an antenna pointed at Mt. Dandenong, however, I can not say if this would work with all dvb-s cards. 

I can now use //tzap// to tune any channel listed in my channels.conf.

//Tzap// needs to know what dvb card (adapter) to use. I have two cards installed.

<code>
rick[~]$ ls /dev/dvb
adapter0  adapter1
</code>

//Tzap// also needs to know which //frontend// and which //demux// to use. My two budget cards can only tune one channel at a time so they only have one //frontend// and one //demux// each.

<code>
rick[~]$ ls /dev/dvb/adapter0
demux0  dvr0  frontend0  net0
</code>

Tzap uses //adapter0//, //demux0// and //frontend0// by default, so I will only have to specify which adapter to use when tuning a channel. I will also need to tell //tzap// where the //channel.conf// is and what channel to tune. If I want to set up the device //dvr0// for recording an mpeg-ts (transport stream) I should also use the flag //-r//. The device //net0// is used when feeding packets into the network protocol stack, i.e. //streaming// a program.

<code>
rick[~]$ tzap -a 0 -c /etc/channels.conf -r "ABC1" 
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
reading channels from file '/etc/channels.conf'
tuning to 226500000 Hz
video pid 0x0200, audio pid 0x028a
status 01 | signal 2a2a | snr 8000 | ber 00003fff | unc 00000000 | 
status 1f | signal 2b2b | snr ffff | ber 00000000 | unc 00000000 | FE_HAS_LOCK
status 1f | signal 2b2b | snr ffff | ber 00000000 | unc 00000000 | FE_HAS_LOCK
status 1f | signal 2b2b | snr ffff | ber 00000000 | unc 00000000 | FE_HAS_LOCK
<snipped>
</code>

Once tzap has tuned the channel it will remain tuned until the process is terminated. Whatever is being broadcast on the tuned channel is available via dvr0 as stdout.

<code>
rick[~]$ cat /dev/dvb/adapter0/dvr0
���,j����{
          ���V12��W1���J��&���G�\���F���k�JjP�)6�)[]]lc�Q���L▒��Ǡ[DE�q�#
V+nx�:�Z�q��nzV��63k�m���[Wdf��Y,�a�m������                             ���F�mi"3a[W��j:�=�J�+
                                           n?>Ѵ�F���g���<E���gޒ�7�2*m�2F�=����]�0-��:eȱK▒�d����͒����G▒-�X�#5�▒����G��0�cW�b�0��Hгڳ
V&0¶s
     V�Ȕ{!��,F▒���+K��Ŕ��a��[V��1Xd��0���Z�sŌ0ٱ��D?�x @-��
                                                          )�@?��?��,[=&hE!2p\�C`@��e▒�KS��B=k1�`���A�2pmn<:6��G�8�@���(�;{��k����lʏ▒���{?sz��e���U��Ã
         V��$Z�i��ݬ,�)3h�-�h[L��6���w��G����P�9��Oe�M�t.l=�L���6���l|�D�Tؾ�ݖK�:���w���צ���O��j&B[0���▒ɘ��6����&+L�TFVG▒6�Q��˘�@����z�G0�V�hbcc-�s��b���X^[[?1;2c^[[?1;2cX�F��Z)��O�X�
٤��)▒ O�"0�#  �0��f@Ɔ2����
�ˌ#
<snipped>
</code>

Using cat to stdout is pretty useless but dvr0 can be redirected and saved as a transport stream (.ts) on disk or accessed by an application and viewed in real time by opening up another terminal and running the second command. The following will  redirect stdout from dvr0 to a file that can be either viewed as is or encoded to some other format.

<code>
rick[~]$ cat /dev/dvb/adapter0/dvr0 > video_name.ts
</code>

The next command redirects stdout from dvr0 to stdin xine which will then open up in a window.

<code>
rick[~]$ xine stdin://mpeg2 < /dev/dvb/adapter0/dvr0
This is xine (X11 gui) - a free video player v0.99.5.
(c) 2000-2007 The xine Team.
</code>

The command to access dvr0 with mplayer is even simpler.

<code>
rick[~]$ mplayer /dev/dvb/adapter0/dvr0
MPlayer 20101218-4.5.1 (C) 2000-2010 MPlayer Team

Playing /dev/dvb/adapter0/dvr0.
TS file format detected.

VIDEO MPEG2(pid=2307) AUDIO MPA(pid=2308) NO SUBS (yet)!  PROGRAM N. 0
VIDEO:  MPEG2  720x576  (aspect 3)  25.000 fps  10000.0 kbps (1250.0 kbyte/s)
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffmpeg2] vfm: ffmpeg (FFmpeg MPEG-2)
==========================================================================
==========================================================================
Opening audio decoder: [mp3lib] MPEG layer-2, layer-3
AUDIO: 48000 Hz, 2 ch, s16le, 256.0 kbit/16.67% (ratio: 32000->192000)
Selected audio codec: [mp3] afm: mp3lib (mp3lib MPEG layer-2, layer-3)
==========================================================================
AO: [oss] 48000Hz 2ch s16le (2 bytes per sample)
Starting playback...
Movie-Aspect is 1.78:1 - prescaling to correct movie aspect.
VO: [xv] 720x576 => 1024x576 Planar YV12 
A:39429.8 V:39429.8 A-V: -0.000 ct: -0.345 298/298  5%  0%  0.4% 0 0
<snipped> 
</snipped>
</code>

As I mentioned above, I sometimes watch dvb in real time with xine but using tzap in one terminal and then running xine from a second terminal is overkill. However, I do use mplayer's encoding/decoding tool, mencoder, to access dvr0 and encode the transport stream to an mpeg-ps<sup>2</sup> (program stream) on the fly before it is saved to disk.

Except for the inclusion of encoding instructions and a path/name for the out file, the mencoder command is the same as for mplayer, mencoder [/path/dvrX].

<code>
rick[~]$ mencoder -oac copy -ovc copy -of mpeg -mpegopts format=dvd /dev/dvb/adapter0/dvr0 -o video_file.mpg
MEncoder 20101218-4.5.1 (C) 2000-2010 MPlayer Team
success: format: 0  data: 0x0 - 0x0
TS file format detected.
VIDEO MPEG2(pid=2307) AUDIO MPA(pid=2308) NO SUBS (yet)!  PROGRAM N. 0
VIDEO:  MPEG2  720x576  (aspect 3)  25.000 fps  10000.0 kbps (1250.0 kbyte/s)
[V] filefmt:29  fourcc:0x10000002  size:720x576  fps:25.000  ftime:=0.0400
==========================================================================
Opening audio decoder: [mp3lib] MPEG layer-2, layer-3
AUDIO: 48000 Hz, 2 ch, s16le, 256.0 kbit/16.67% (ratio: 32000->192000)
Selected audio codec: [mp3] afm: mp3lib (mp3lib MPEG layer-2, layer-3)
==========================================================================
PACKET SIZE: 2048 bytes, deltascr: 43885
videocodec: framecopy (720x576 24bpp fourcc=10000002)
audiocodec: framecopy (format=50 chans=2 rate=48000 bits=16 B/s=32000 sample-1)
Limiting audio preload to 0.4s.
Increasing audio density to 4.
Writing header...
INITV: 0.200, 0.160, fps: 25.000
Pos:   1.0s     26f ( 0%) 24.88fps Trem:   0min   0mb  A-V:-0.084 [0:256]
<snipped>
</code>

I could just save every thing I want to watch as a transport stream but the overhead running mencoder is very minimal. Additionally i prefer to save shows as mpeg-ps videos and I can edit out commercials from using a very fast no frills gui application , gopdit, that was developed specically for editing program streams<sup>3</sup>. If I record an hour long show as an mpeg-ts I would later have to spend as much as another hour encoding it to mpeg-ps before I can edit it. Better just to encode o the fly.

Using two terminals and remembering commands, options and syntax gets to be a bit too much so I'll close this tutorial with an example script that illustrates how the commands tzap and mencoder can be used in a script to record a dvb broadcast. To use this script you would have to edit the variable declarations to suit and run it when the show is about to begin. I have written an interactive script that parses channels.conf, presents a list of channels for selection and then prompts for how long to save, where to save, etc. 

I'll present that script later on in my series of bash tutorials.

<code bash>
#!/bin/bash
# zap-men
# Edit variables to suit.
dvb_card=1
video_dir=/multimedia
chnl_cnf=/etc/channels.conf
channel=ABC1
duration=3600
name=luther-abc-friday.mpg

# Tune in and lock channel
tzap -a $dvb_card -c $chnl_cnf -r "$channel" &
tzap_pid=$!

# Give tzap time to tune in and lock channel
sleep 2

# Encode on the fly
mencoder -oac copy -ovc copy -of mpeg -mpegopts format=dvd /dev/dvb/adapter$dvb_card/dvr0 -o /$video_dir/$name &
mencoder_pid=$!

sleep $duration

kill $tzap_pid
kill $mencoder_pid

# end of script
##################################################
# Note:
# The ampersand "&" is used  tzap so that it will run in the background. If not.
# the script will never proceed to the mencoder command. Likewiseand the 
# mencoder command is follwed by an ampersand else the script will never
# proceed past that command to run the duration of recording and the shut 
# down.
</code> 

----
Rick Miles

03 March 2012

----

//<sup>1</sup> I am using a Dvico Fusion HDTV DVB-T Lite pci card and a WinFast DTV1000 T pci card. The Dvico was certainly not budget priced when I purchased it 7 or 8 years ago but feature wise today it would be considered a budget card. The Winfast was purchased 5 or 6 years ago for $35.00. The only difference was that the Dvico came with windows software and a remote that I never used.//

//<sup>2</sup> The mencoder options in this command will encode to a very basic mpeg-ps DVD standard. They would not be suitable for a .VOB quality mpeg.ps. I use a different set of options in a script that will also shrink the video to less than 4.2GB if required. See [[http://www.mplayerhq.hu/DOCS/HTML/en/menc-feat-vcd-dvd.html]] for more information on using mencoder to encode DVB quality videos.//

//<sup>3</sup>3 I have been using gopdit (GOP accurate eDITor) just about as long as I have been recording DVB TV. Gopdit is a is a fast and simple program that lets you cut and merge mpeg-ps files at GOP (group of pictures) boundaries without reencoding. It supports no other file types or operations. The fact is that it is simple and only does one video editing task is on one file type is probably why it is relatively unknown. You can find gopdit at [[http://gopdit.ath.cx/]]//