[pvrusb2] Noise

Sun Apr 21 11:49:33 CDT 2019

Some things about firmware...

First, when comparing firmware versions, it is more reliable to compare 
md5 sums than just modification date and file size.  The modification 
date is effectively meaningless and there are versions floating around 
that have the same size.

Second, while the pvrusb2 driver web site is, well, quite long in the 
tooth, everything there about dealing with firmware should still be 
valid (well maybe except the part about ivtvdriver.org - I don't manage 
that site and I have looked there in years).  Keep reading...

Third, there is a tool you can grab, called fwextract.pl (yes written in 
perl, long before I learned python...) that does an intelligent job of 
physically extracting useable firmware images straight out of the 
windows driver package that would have come with your device.  The tool 
works via extensive use (some might say abuse) of md5 sums to locate and 
verify specific firmware images.  While you can of course just use 
whatever you find on the net or that came with your distro, if you want 
to use the exact firmware images that came with your hardware, you can 
always use fwextract.pl to get at it.  This page includes a discussion 
about using that tool:

http://www.isely.net/pvrusb2/setup.html#Firmware

The reason I bring up this last bit is that I believe for the HVR-1950 
the cx25840 firmware needed for it may conflict with the cx25840 
firmware needed for other devices and that the common one(s) floating 
around might be a problem for the HVR-1950.  This was something I had 
become aware of shortly before I had stopped working on the driver and 
never really learned the full story.  So if there's any question about 
what is the "right" cx25840 firmware image to use, the answer may very 
well be just to use fwextract.pl on your hardware's bundled driver 
package and therefore get the same precise version that was intended for 
that hardware when run under Windows.

BTW, if you look at fwextract.pl itself, you will see a data table 
listing all the firmware images it "knows" about, complete with md5 
sums.  You can, if you want, compare that with md5 sums of the firmware 
images you happen to be using.  That will at least tell you if we know 
the pvrusb2 driver has been used with the firmware you are trying.

Note that for the pvrusb2 driver there is not just one firmware image.  
There are multiple parts in the hardware that each need firmware images.  
The exact needs depend upon the model of course.  The web page I linked 
above has more information on that.

  -Mike

On Sun, 21 Apr 2019, Diego Rivera wrote:

> Interesting question: which firmware version are you using (and how big is it in bytes)?  There are
> several versions floating about out there, and I know only one is the "latest and correctest" one.
> Perhaps in your travails of O/S upgrades over the years you've mistakenly installed the wrong one?
> Cheers...
> 
> On Sun, 2019-04-21 at 08:55 -0500, Mike Isely wrote:
> > The pvrusb2 driver is supposed to select the audio input in conjunction with the video choice. 
> > There is a map in the driver that, based upon the particular model, should be selecting the
> > correct audio input for you when you select the "overall" input. It has always been like that.  If
> > there's a problem there now with that, well, it is another thing that needs to be
> > investigated.More stuff to dig out, with no extra time in which to do it :-(Sent from my T-Mobile
> > 4G LTE Device-------- Original message --------From: Jan Ceuleers <jan.ceuleers at computer.org>
> > Date: 4/21/19  8:21 AM  (GMT-06:00) To: pvrusb2 at isely.net Subject: Re: [pvrusb2] Noise Mike,Thanks
> > for your reply.Given that in the past it was possible (in fact necessary) to select theaudio input
> > and that this is no longer possible/necessary now, am Iright in thinking that the driver programs
> > the hardware to add all audiosources together on the assumption that only the "correct"-one
> > willactually be producing an audio signal and the others will be silent?If so, are there
> > circumstances under which this assumption might be false?Again if so, is there anything I can do
> > about that? For example, in myuse case (where I'm only recording from line in and composite video
> > in)can I disable certain components that aren't being used? For example getrid of certain firmware
> > images, or use certain pvrusb2 module parameters?Thanks, JanOn 21/04/2019 14:54, isely at isely.net
> > wrote:> Jan:>> That's an odd symptom.  Getting audio from an RF signal actually has a > longer
> > processing path than audio from the line-in port.  In fact, > there should be very little (if
> > anything) involved with the line-in port > that isn't also involved with processing audio from an
> > RF signal.  In > either of those two cases, the audio is processed by a separate chip > (cx25840
> > IIRC) and the result of that is what is fed into the mpeg > encoder chip.  Once past the cx25840,
> > there's no difference in the > datapath.>> There's a separate driver for the cx25840, which the
> > pvrusb2 driver > employs, which is part of the v4l2 subsystem as a whole, so any problem >
> > involving audio like you describe should also be likely with any other > video capture driver that
> > also happens to use a cx25840.  I know this > isn't being very helpful, but it does suggest that
> > looking for other > online chatter involving that part might reveal another clue.>>   -Mike>>> On
> > Sun, 21 Apr 2019, Jan Ceuleers wrote:>>> Dear list,>>>> I am seeking some help with an audio
> > defect that afflicts some>> recordings made using Hauppauge PVR 1950 devices.>>>> I have two
> > mythtv backends:>>>> - the slave backend has three 1950s that record from analogue cable.>> Audio
> > recorded from these tuners is fine.>>>> - the master backend has two 1950 PVRs that record from
> > set-top boxes>> (i.e. from the composite video input and line audio inputs). All>> recordings made
> > using these two tuners suffer from an audio defect as>> described below.>>>> The audio defect is a
> > clearly audible repetitive "whistling" noise, with>> a periodicity of about 1 second. This noise
> > is not present on the audio>> signal that goes into the PVR.>>>> I have tried many variations of
> > v4l2-ctl -d$device -f $freq without>> effect (and have settled on 450 MHz as the frequency). The
> > point of>> doing this is that I want to exclude noise from the channel the analogue>> tuner
> > happens to be tuned to.>>>> Many moons ago a pvrusb2 device had multiple audio inputs from which
> > one>> could select the right-one using v4l2-ctl -d$device>> --set-audio-input=$audiodev , with
> > valid values for audiodev being 0, 1>> and 2. The correct setting for my use case was 1. This is
> > no longer the>> case: the device presents only one audio input which is numbered 0.>>>> I'd be
> > grateful for any hints.>>>> Thanks, Jan>>>> _______________________________________________>>
> > pvrusb2 mailing list>> pvrusb2 at isely.net>> 
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-- 

Mike Isely
isely @ isely (dot) net
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