[pvrusb2] saa7115 1-0021: Video signal: bad

[Mike Isely]

On Thu, 21 Feb 2008, dan wrote:

> Thanks for the reply...I had read the ref'd page(s)...but as you have 
> found its hard to write it and its even harder for a stubborn old man to 
> read it with any degree of comprehension... Thanks for holding my 
> hand..or as we used to say ''''RTFM""". Off subject but you will 
> appreciate: My first technical training was; age 18, navy comic books at 
> naval training center for electronics...This worked as I had no math, 
> science or knowledge...
> Second instance; age 26, junior engineer for aerospace co----They 
> supplied tech writer with 30 years experience to turn my design into 
> tech manual for air force...Last (recent); age 72,  puppy linux, 
> mepis....these have built short, concise, location (problem ?) specific 
> popups with well written, short, descriptive  items that really help 
> those of us that can't or wont read in the depth you have done for the 
> driver you built.....This is not a critisism of your documentation, just 
> to show understanding of your frustration..It would be wonderful of you 
> could access an old experienced tech writer....but again "that's linux".....
> 
> I spent the morning reading and trying to get tv working...I tried 
> kdetv, kmplayer, mplayer, kino..etc. but I have been unable to set it 
> up(or too lazy to find the setups to set it up). I googled and forumed 
> and wikied for a easy way to setup mythtv....some referrals to synaptic 
> appear but my mepis 7 install does not download any mythtv packages. I 
> downloaded the tarball from mythtv site and one day may try to unball 
> and compile??? it.

One significant issue that you can't escape is that the pvrusb2 driver 
emits an mpeg2 video stream via the V4L API.  In order for an app to use 
this it has to be able to handle mpeg2.  And there are precious few V4L 
apps that can do this - just xawtv and mythtv are the only two I know 
about.  There are some other apps that can also just "read" a random 
path and decode mpeg2 from that - this is how mplayer can be made to 
work.  Unfortunately that's about it.

There's a much larger set of video apps that can decode mpeg2 from the 
DVB API.  But unfortunately this driver doesn't use the DVB API.  I'd 
like very much to "fix" that issue, and there's been some progress along 
this line, but DVB is a complex beast and there are some aspects to it 
(like it really is meant for true digital TV receivers) that may yet 
scuttle this ability.  I'm still learning however...


> 
> Tried mplayer (yes, w/o the kde)....results:
> 

   [...]

In amongst all that noise (mplayer output is very noisy), I see this:

> MPEG-PS file format detected.
> VIDEO:  MPEG2  720x480  (aspect 2)  29.970 fps  8000.0 kbps (1000.0 kbyte/s)

   [...]

So it looks like it worked for you.

> 
> Don't understand what this means or at least at a loss as to what to try.

mplayer tries to open and do a lot of things, and it gets noisy if 
certain things don't work.  But it's not fatal.  For example, mplayer 
will try to talk to LIRC so you can use an IR remote with it, but if it 
fails to open a channel to LIRC it complains loudly (and then goes on 
without it).  That's OK.  Another thing is that when you stream a 
real-time feed like this, there's really no "beginning" to it - mplayer 
just starts getting data at some point.  So it may take a second or so 
for mplayer to lock on.  That's ok too.

Did you get a picture with it?  You still might not have since you 
didn't try to tune the device.  When the driver comes up it will by 
default first try to tune US broadcast frequency channel 7.  If you have 
an antenna connected and there *is* a channel 7 in your area then you 
should have seen something.

>  
> I am using kernel 2.6.22-1-mepis-smp

I am unfamiliar with mepis, but assuming they've just repackaged the 
vanilla 2.6.22 kernel then that should be fine.


> 
> It looks like I will have to use mplayer if I get tv...I suspect I have 
> no tv channels or freq tables spec'd...but don't know what you mean by 
> using Sysfs to control it..  I looked at your info but cannot figure 
> what I type at term or ????

There's another page on the site that talks about sysfs.  See here:

http://www.isely.net/pvrusb2/usage.html#sysfs

Basically "Sysfs" in this context is a small directory hierarchy where 
each file is actually a virtual node that directly controls an aspect of 
the driver.  By cat'ing files in that area you can inspect driver state 
and by echo'ing new values into files there you can control driver 
state.  Look at that page now and see if it makes more sense.

You should also be able to use xawtv, but you're going to have to build 
it first since you need a 4.x version of it.

Of course, the real use for this driver is mythtv.  I *have* built 
mythtv from sources in the distant past, but I've long since given up on 
that particular form of self-torture.  I run Debian here and instead 
install mythtv from prebuilt Debian packages available at 
www.debian-multimedia.org.  Since I don't know about mepis, I don't know 
what packaging style it expects.  But in your shoes I'd probably be 
hunting around mythtv.org (in addition to perhaps a google search like 
mepis+mythtv) for some answers.

  -Mike

-- 

Mike Isely
isely @ pobox (dot) com
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