Sorry,
I forgot to mention that I am using mythtv 0.18.1.20050510-1, installed
via Gentoo's portage (Gentoo calls this 0.18.1-r2). I imagine you would
all want to know that :-)
Michael
Michael Cowell wrote:
Hi all,
I am also experiencing a problem like this. I have the following setup:
AMD Duron 1 GHz
384 MB SDRAM
Twinview DVB-T capture card
Pinnacle PCTV bt878 based capture card
SBLive! emu10k1 based audio card
Linux distro is Gentoo. Kernel version is 2.6.12-gentoo-r8. I am using
unpatched V4L.
Obviously the popping / clicking occurs only with the analog card.
You might think my box is outdated, that's because it is!
Interestingly I had this same hardware running MythTV 0.15 a while
ago, also with Gentoo and a 2.6 series kernel (I think it was around
2.6.2 back then), but there was no clicking.
My CPU does not max out when doing analogue recording. I have tried
ALSA and OSS, and have changed recording levels extensively. This did
not fix the issue.
I don't mind the popping too much because I only use the analogue card
when the digital one is busy.
I mention this because it seems to me that my experience indicates that:
1. This does not appear to be a hardware fault (I had clear audio
going using this hardware before software upgrade).
2. This does not appear to be a capture card problem (my capture card
is different to Sergio's, at both the board and chipset level).
3. The emu10k1 chipset is a common factor here. Maybe that is the
problem. I imagine the driver has had a lot of work since 2.6.2.
If I can provide any more information please let me know. This problem
interests me because I can't see a clear reason for it occurring. The
distortion "sounds analogue" (like clipping / RF interference), but
DSP is so advanced these days that this could easily be a digital
hardware / software issue.
Thanks,
Michael Cowell
Sérgio Gomes wrote:
David Ellis wrote:
Lower your volume level on the card setup in mythsetup.........I
think the
problem is with an input volume level that is too high.
David
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Sérgio Gomes
Sent: Friday, September 02, 2005 5:00 PM
To: [email protected]
Subject: [mythtv-users] Crackling and popping in non-PVR analog card
-- I
think I can say it's MythTV's fault
Hello everyone!
I'm probably one of the very few people left with a non-PVR analog
card (a simple Hauppauge WinTV Go, based on cx8800). The audio goes
from the TV card to the sound card via a simple external stereo
cable, as I'm sure is the case in many setups out there.
Now, I have been having a problem with audio on my MythTV since I
installed it yesterday: I get a lot of crackling and popping in my
recordings and in LiveTV. I've been running several tests.
Outside MythTV:
- The audio gets to the sound card in great quality: if I turn on
playback of the line-in channel, the sound is perfect
- It is also not the recording hardware of the sound card that is
ruining the sound, as both "record" and "arecord" record perfect sound
- "record" and "arecord" still record perfect sound with high CPU
and disk loads
- "record" and "arecord" record perfect sound whether or not video
is playing (with XawTV, for instance)
- If I start recording sound then start mythfrontend and select
"Watch TV", it won't get any sound (understandable, the device is
busy), but the "record" or "arecord" program will keep on recording,
and the sound is, once again, perfect
- Recorded MythTV shows play with crackling in mplayer
Inside MythTV:
- The amount of crackling (or at least the loudness) goes up with
the loudness of the broadcast; if it's quiet there's almost no
crackling, but if there are a lot of people talking or loud sounds,
there is a lot of crackling
- Happens with ALSA and OSS
- Happens with MJPEG and MPEG4
- Happens with or without "Agressive Sound Buffering"
- Happens with both WAV and MP3, at any of the available rates
- Happens with or without internal volume controls, at any level
- Music and videos play without any problems
- The amount of crackling goes up with the quality of the video;
there is almost no crackling at 160x160, but a lot of it at 768x576
So, given all this I think we can rule out any interference on the
sound from external sources, hardware or other software, and assume
the problem is limited to the TV functionality in MythTV. My guess
would be that the sound is being clipped due to volume adjustments
inside MythTV, and is only then recorded, assuming that MythTV does
some volume processing on the sound (even if just boosting it).
Now, this is all fine and well and a good theory until the last
point. I don't understand why the problem gets worse with higher
video resolutions. That completely ruins my theory. With that in
mind, I guess the problem could only be some kind of multiplexing or
demultiplexing bug (probably multiplexing, because for it to be a
demultiplexing bug it would also have to be present in mplayer), but
that wouldn't account for the problem getting worse on loud samples
(since WAV is constant bitrate).
So, I'm hoping someone who knows MythTV better than me can help me
out with this... I'll gladly provide recording samples if anyone
wants them. Here are my PC specs:
- Athlon 64 3200+
- NForce 3 motherboard (ASUS)
- Gentoo Linux with 2.6.12-r5 gentoo-sources kernel
- video4linux CVS (due to some cx8800 problems with the release
version). --> shouldn't be the problem because of all the above reasons
- WinTV Go 2 with cx8800 chip
- Audigy 2 ZS (snd-emu10k1 module), with hardware mixing
- MythTV 0.18.1 compiled from source in AMD64 (as the rest of my
system)
- Using PAL BG
Thank you for bearing with me through this exhaustive description.
Sérgio Gomes
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Well, I've tried that and it still happens :-/
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