[linux-dvb] HVR3000, cx88_alsa, crackly audio

Robert Longbottom RobertCL at iname.com
Thu Dec 21 15:14:54 CET 2006

On Wed, December 20, 2006 4:30 am, Steven Toth wrote:
> Robert Longbottom wrote:
>> Hi again!
>> After much messing around I've managed to get the HVR3000 to working
>> using Steven Toth's tree.
>> I still need to unload and reload the tuner module a few times on each
>> boot to make it pick up the TDA tuner chip, but it works once it has
>> been detected.
>> My problems with no audio was because I was using the wrong TV-norm :-/
>> ooops.
>> Now it is working, I have audio, but every now and again I get crackling
>> or distorted audio.  This is when I'm watching TV (or  recording) using
>> MythTV.
>> Has anyone else experienced crackling / distorted audio (I guess on
>> anything using cx88_alsa) and how did you fix it?
> I'm playing catchup on the ML. It's good to see people have the HVR3000
> patches limping/running.
> How would you categorize the audio noise and is their any kind of
> pattern to when it appears/disappears, or to the type of noise?

I did a bit of experimenting last night with the intention of recording a
sample and posting it but it never quite happened.

I'm running MythTV and I have two capture cards in the PC (the HVR3000 and
a fairly old Hauppauge PCI card (bttv kernel module))  Both are connected
to the same (analog) source.  The HVR card seems fine when it is the only
card in use, but when both cards are in use the HVR audio crackles - kind
of like it is tuned slightly off station.  Also during playback it kind of
sounds like the audio data is longer than the video data and it is being
"squashed" so that it stays in time with the picture.  The system is under
fairly heavy load in this case with 95% - 100% CPU in use.  The bttv card
however seems to manage to capture audio fine under these circumstances.

I decided to take MythTV out of the equation, so I setup xawtv displaying
the picture and set off "arecord | aplay" and everything seemed fine!  So
I'm wondering if the problem is MythTV related, or maybe due to the fact
that they system is under high load.  I'm sure I used to have the problem
that when doing this (xawtv + arecord) the audio from the HVR would end up
out of sync really quickly, like it was getting too much (or too little)
data back and that was causing it to drift out of sync with the picture -
but this didn't seem to be happening last night.

None of that is really very helpful I'm afraid!

Since you are back looking at the HVR code though :-))  I do have two
other problems...

1) The TDA tuner on the HVR rarely gets detected, and I have to rmmod
tuner && modprobe tuner a couple of times to get it to appear.  Until I've
done this analog TV tuning doesn't work.

2) I've been trying to get DVB-S to work.  Basically, it seems to be
working.  I've had a few problems getting it to tune into certain channels
and get a lock, but I can usually get it to lock on eventually by turning
on my satellite STB, tuning the channel on there and then turning it off

Also, the picture quality on the HVR has a lot of artifacts in it (pretty
much all of the time) whereas my STB displays the picture fine with no
artifacts at all.  My sat-dish is connected to my STB, which has a
loop-through connection which I have connected to the HVR card, so the
signals should be the same quality (I assume).  The picture via the HVR is
watchable most of the time, but the artifacts are pretty annoying (and
usually seem to be across the middle of the screen rather than round the
edges where it wouldn't matter as much!)

If I can do anything to help testing wise, let me know as it would be nice
to get the DVB-S working well then I can hopefully get it running in


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