[pvrusb2] remote, radio and other issues

[Mike Isely]

On Sun, 25 Feb 2007, leonardo wrote:

> 
> I have not seen that problem.  However (and I imagine this doesn't help 
> much) the only involvement of the pvrusb2 driver in IR is at the very 
> lowest level: The pvrusb2 driver just provides an I2C control path to 
> the IR receiver chip; the actual driver for the IR receiver comes from 
> elsewhere (the lirc package or V4L itself depending on how you have 
> things set up).  For 24xxx devices, the pvrusb2 driver also emulates 
> the presence of the IR receiver chip but the outward result is the 
> same.
> 
> ok, I noticed that if I fire up irw I see the right code of the last botton pushed, 
> so I'm starting to think it's related to irexec. but can't figure it out now.
> Somebody has an .irexec file to share?
> 
> > 
> > then, I'd like to set up a media center using an Xbox, but I've seen there are some 
> > issues with that. Are the issues still present and relevant?
> 
> So the short summary is that the pvrusb2 driver will work on xbox, but 
> it takes some tweaking of a few xbox I2C drivers first.
> 
> this seems enough for wasting 80€ for an old xbox, see what happens and
> then come to knock again... :-)
> One more thing.. how does the driver work with an usb 1.1 port as the xbox has?

The pvrusb2 driver does not actually "care" about the USB speed.  To the 
driver the bits are the same only slower.  The default capture settings 
are conservative enough that the device should work OK over USB 1.1.  
But realize that you're probably going to be limited to only one PVR 
USB2 device at the end of that cable (i.e. don't insert a hub and more 
devices and expect things to still work smoothly).


> 
> 
> > I'm having problems with FM tuner, I can read from the device with mplayer and use cat to set
> > the channels, but I have no luck with kradio.. again is this I should work out with 
> > my configuration?
> 
> You will not be able to play the audio through kradio.  However you 
> should be able to use kradio to tune the device and then another app 
> (like mplayer) to play the audio.  Also realize that the PVR USB2 
> 
> ah.. I was missing that part. 
> 
> hardware uses a separate F-connector for FM radio reception.  If you 
> still have the coax connected to the TV input F-connector, then the 
> radio won't receive much :-)
> 
> I didn't quite get this, there are two separate connectos so why should 
> one interfere with the other?  anyway, mplayer works..

It's not a case of interference.  It's that there are different circuits 
(apparently) for FM radio tuning versus TV tuning.  It doesn't matter 
what's coming in the F-connector for the TV when tuning the radio.  It 
_does_ however matter what you have coming in the F-connector for the FM 
radio.  You can certainly connect to both at once, with a suitable 
splitter.


> The fact that kradio doesn't work is due to what? that it cannot read from an 
> mpeg stream? it should produce some pcm or mp3 code?

There's some V4L history here.

My understanding is that early and/or cheap radio devices in V4L just 
emitted the audio out an analog jack on the back of the card.  There 
simply wasn't a digital means to pick up the audio data.  Even today 
cheap TV tuners work the same way - the software grabs the video frames 
but the audio is line-out from the back of the card.  Typically what you 
did in those cases was to connect a loop-around cable from the capture 
device's line-out into your sound card's line-in.  This is how apps like 
tvtime expect to work - they don't bother at all with the audio beyond 
messing with the mixer and letting the sound card route the signals.

Being able to grab PCM data from a radio card came later.  Thus radio 
apps don't always (or at all) expect to be able to grab audio data.

In the case of the PVR USB2, there is no "line out" analog jack, and we 
(currently) can't grab PCM directly.  Instead, what you get is an mpeg 
stream whose audio component just happens to carry the FM radio station 
you're tuning.  V4L apps unfortunately don't generally know about 
reading mpeg stream data from a V4L device, and certainly it's going to 
be unlikely that something like kradio would know how to do this.  So 
for something like kradio, the program just has to treat the device like 
an "old radio card" and assume that somebody else is handling the actual 
audio - only in this case instead of a loop-around cable it's mplayer 
grabbing the stream and decoding it into something that can be sent 
digitally to your sound card.

  -Mike


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