Webcamd : Can it support dvb-s/dvb-s2 usb devices ?

Juergen Lock nox at
Tue Apr 13 20:48:55 UTC 2010

On Mon, Apr 12, 2010 at 11:53:27PM +0200, Juergen Lock wrote:
> In article <201003311322.56988.hselasky at> you write:
> >On Wednesday 31 March 2010 10:26:09 christophe LE ROUX wrote:
> >> Hello,
> >> 
> >
> >Hi,
> Hi!
> >
> >> As i can read on some web pages, webcamd can support webcam and dvb-t
> >> devices who have a linux driver.
> >> What about dvb-s (or dvbs2) usb devices ?
> >
> >Yes, many are supported, but some are not. Please see the main Makefile in 
> >webcamd.
> >
> >> i think about Tevii S650 ( or S660 ) with ds3000.c linux driver, Pinacle
> >> PCTV 452e Sat HDTV Pro USB with pctv452e.c linux driver or Technotrend
> >> Connect S2-3600 HDTV-S2 USB ( with pctv452e.c linux driver too ).
> >> 
> >> Another question,
> >> If webcamd can support these usb devices, can i use mythtv port with ?
> >
> >I have not tried this yet. If mythtv uses the linux DVB header files, then 
> >yes.
>  For the OP (and other readers:)  I haven't tried mythtv yet but after
> some hacking and a longer debugging session on #bsdusb I got a PCTV 452e
> Sat HDTV Pro USB working using szap-s2,
> checked out from hg and built by:
> 	gmake INCLUDE=-I/usr/local/include
> and the CFT mplayer port (looks like it still isn't committed),
> pointed at the dvr0 device:
> 	mplayer -demuxer lavf -cache 8192 /dev/dvb/adapter0/dvr0
>  kaffeine worked too but the version in ports doesn't yet know dvb-s2,
> (and even on Linux where I have a newer kaffeine it still has audio
> issues on the hd channels.)  vlc's builtin dvb support was useless with
> this tuner (and caused us lots of useless debugging looking for a problem
> in webcamd because vlc behaved like it got a corrupted stream...),
> what does `work' is pointing vlc at /dev/dvb/adapter0/dvr0 together
> with szap-s2 like mplayer, but vlc used too much cpu on hd channels so
> they weren't really watchable.  (unlike mplayer which played 1080i
> just fine using ~85% of one core and only xv on xorg's radeon driver
> on a PhenomII cpu...)
>  About szap-s2:  I ran it similar to this:
> 	./szap-s2 -V -n 6 -p -t
> and on some hd channels I need -b too or mplayer would get no audio.
>  -t is a new option I just added to pass teletext thru (vlc can display
> it, this needs -V because the teletext pid is only in the VDR channel.conf
> format), that patch I put here:
>  hps now has updated the webcamd svn to use only the pctv452e driver
> out of the s2-liplianin repo that I originally used entirely in place
> of the one (for some reason the pctv452e-related drivers
> are still missing in upstream Linux) and I just tested that svn version
> today:
>  I haven't tried building w_scan on FreeBSD yet
> but hps said he only needed to fix include paths - you need it if you
> don't have a channels.conf yet, I took mine from Linux with some
> updates off the web.  kaffeine can scan too, but as I said this
> version doesn't know dvb-s2, and also it uses its own channel list
> format.
>  Oh and a poor man's way of recording is to use szap-s2 and then
> cat /dev/dvb/adapter0/dvr0 to a file...  (you probably can play it
> with mplayer while it's still being written if you wait a little
> at first if you want to find out when the show you want ends.)

I forgot to say you need the svn version of cuse4bsd too, there was
a bug in the ioctl handling that broke ioctls that pass no data
(_IO) like dvb-s uses. (FE_SET_TONE, FE_SET_VOLTAGE...)

 And I played with w_scan a bit now and found three things:

1. the FE_GET_PROPERTY ioctl in <include/linux/dvb/frontend.h> needs
to be _IOW not _IOR - yes this is broken on Linux too but they do
a workaround (they just always do the copyin) in
linux/drivers/media/dvb/dvb-core/dvbdev.c:dvb_usercopy(), see the
comment /* some v4l ioctls are marked wrong ... */ here:

 And I think a workaround is impossible on FreeBSD since the copyin()
of the ioctl data is handled in the ioctl syscall directly not in the
drivers like on Linux:

so I'd say we'll have to patch our copies of the Linux includes if
we want FE_GET_PROPERTY to work. :(  (And I dunno if that's the
only broken one...)

2. w_scan for some reason seems to miss random transponders when
I use the updated svn webcamd that uses the pctv452e drivers in the v4l-dvb tree instead of just the entire s2-liplianin tree
like I originally did; I say `random' because if I do another scan
then other transponders are missing...  Using the s2-liplianin tree
I get a channels.conf with around 1170 lines, using the svn webcamd
I once got 762 lines, another time 884...  And I really don't feel
like debugging this because the reason could be anywhere in whatever
other fixes there are in the s2-liplianin tree compared to v4l-dvb,
so I think we really need something like a knob in the webcamd port
to select which tree to use.

And 3. there's a bug in w_scan that breaks scanning dvb-s when using
the old dvb api:  (which it will assume when FE_GET_PROPERTY doesn't
work; and also after applying this fix using the old api will still
make it skip dvb-s2 transponders.)

--- a/scan.c
+++ b/scan.c
@@ -1640,6 +1643,10 @@ static int set_frontend(int frontend_fd,
 		case 0x0302:
 			verbose("%s: using DVB API 3.2\n", __FUNCTION__);
 			copy_fe_params_new_to_old(&p, &t->param);
+#if 1
+			if (t->type == FE_QPSK)
+				p.frequency = intermediate_freq;
 			if (ioctl(frontend_fd, FE_SET_FRONTEND, &p) == -1) {
 				errorn("Setting frontend parameters failed (API v3.2)\n");
 				return -1;


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