[mythtv-users] Occasional metallic sound when recording

[Eloy A. Paris]

Hi,

I sent the message below to the alsa-devel mailing list. One of the
responses (see below) suggests it might be a problem in MythTV. I
doubt it but I just wanted to post here to see if anyone has
experienced something similar. I searched the archives and didn't find
anyone reporting a similar problem. This is very annoying, and I would
really like to solve it because I've recorded several programs that
are hard to understand because of the metallic noise.

Thanks for any pointers.

Eloy.-

========= Original message =========

Date: Wed, 22 Oct 2003 12:22:19 -0400
To: alsa-devel at lists.sourceforge.net
Subject: Occasional metallic sound when recording (cs46xx)

Hello,

I am trying to troubleshoot a very annoying problem I have with a Santa
Cruz Turtle Beach (cs46xx). Sometimes, when recording, the recorded
sound is very metallic. If when I get the metallic sound I run alsamixer
and toggle the capture facility of the ADC on and off, sound is fixed
and back to normal.

This problem happens randomly but is very annoying, specially if I
program my PVR (MythTV) to automatically record a show - the show can
get recorded with metallic sound, which makes it very hard to understand
during playback.

This is not MythTV-specific since I have been able to reproduce the
problem using other applications, like the Gnome sound recorder. It is
unrelated to full-duplex operation since when recording a show MythTV
doesn't open /dev/dsp for writing.

I really have no idea about how to troubleshoot this. I don't think
the problem is hardware, but is driver-related instead.

Any suggestions? Are there any debug switches I can enable to get more
information about the problem? I can recompile the drivers and try
anything. I really want to see this fixed, so if anyone has any ideas
to try just let me know.

========= One reply =========

its almost certainly a software problem in mythTV and gnome sound
recorder. i've written code that does this several times - every time
it takes me ages to figure out why, and then i can never remember when
i do it the next time. its related to off-by-1 errors in processing
incoming audio.

not necessarily, of course, just a point of view.