[MPlayer-users] mencoder: determining cause of audio clipping/noise

[Henrik Eriksen]

Is there any tool that can be used to determine what value is set to
high, causing noise in an mencoder recording?  I.e. something like a
vumeter for all relevant channels?  Doing multiple takes with
different settings, and then listening to the result is a
time-consuming and inaccurate way to find the relevant values.

Currently I have muted every channel, set line-in as "capture", and
the level on the Capture item to 27.  I then get a recording that
sound fairly OK if I run mencoder with (split for readability):

   mencoder -tv driver=v4l2:buffersize=32:input=0:fps=25:\
   forceaudio:alsa:audiorate=44100:amode=0:adevice=hw.0,0:volume=0:\
   width=768:height=576 -frames 125 -cache 32000 -oac mp3lame \
   -lameopts cbr:br=128:vol=0 -ovc lavc -lavcopts \
   vcodec=mpeg4:vqscale=3:keyint=200:vrc_buf_size=8000 -o test.avi tv://

I find it surprising that volume should be 0, but if it is set higher,
more and more noise is included in the audio signal.

tvtime has no problems producing "noise-free" audio.

(I'm using MPlayer-1.0pre2, driver=v4l2 option, kernel 2.4.22 w/kraxel
patch and a saa7134 card)

Regards,
Henrik Eriksen