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 programs1 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
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
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.
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
To create my channels.conf I run scan with the path to au-Melbourne and redirect stdout to a file.
rick[~]$ scan /usr/local/share/dvb/dvb-t/au-Melbourne > channels.conf
The complete channels.config looks like this:
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
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.confto 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.
rick[~]$ ls /dev/dvb adapter0 adapter1
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.
rick[~]$ ls /dev/dvb/adapter0 demux0 dvr0 frontend0 net0
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.
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>
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.
rick[~]$ cat /dev/dvb/adapter0/dvr0
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<snipped>
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.
rick[~]$ cat /dev/dvb/adapter0/dvr0 > video_name.ts
The next command redirects stdout from dvr0 to stdin xine which will then open up in a window.
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.
The command to access dvr0 with mplayer is even simpler.
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>
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-ps2 (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].
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>
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 streams3. 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.
#!/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.
Rick Miles
03 March 2012
1 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.
2 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.
33 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/