VHS capture : frate slows down + bad sound

[cotcot]

I want to capture VHS from an old camcorder with video through composite and audio (mono) through white RCA to 3.5 mm jack microphone input with mencoder on a ubuntu hardy system.
Question 1 :
The VHS tape is 45 minutes. It starts at 25 fps and slows down to 20 fps when the tape is at the end of 45 min. I tried to capture the tape in 1 sequence. The lower the framerate the higher the number of frame drops (although not high in total some 150 frames dropped on 63000 captured). Play back of the capture mpeg is good in the beginning but less smooth at the end.
I capture with this command : mencoder -tv norm=PAL:driver=v4l2:width=720:height=576:input=1:fps=25 tv:// -oac lavc -ovc lavc -of mpeg -mpegopts format=dvd -vf pp=lb/ha/va/dr,hqdn3d,harddup -srate 48000 -af lavcresample=48000 -lavcopts vcodec=mpeg2video:vrc_buf_size=1500:vrc_maxrate=8000:vbitrate=7000:keyint=15:acodec=mp2:abitrate=192:aspect=4/3 -o capture.mpg
Is there anything I can do to keep de framerate constant at 25 fps (PAL) ?

Question 2
The sound level is OK. The sound quality is not OK. It is distorted with high frequency tones. (A speaking voice however can be understood).
Capturing the sound of the same tape with ubuntus default Sound Recorder gives good result (i do not know the command that it uses). I think that there is something wrong with the resampling but I do not know how to modify the mencoder command to get correct sound.
Any suggestions ?

[nm]

Is there anything I can do to keep de framerate constant at 25 fps (PAL) ?
Probably there is a way, but you may need to experiment with MEncoder options a bit. Try adding -fps 25 -noskip to the command line and perhaps remove harddup from the video filters.

I think that there is something wrong with the resampling but I do not know how to modify the mencoder command to get correct sound.
Any suggestions ?Well, have you tried without resampling (remove -srate 48000 -af lavcresample from the command)?

[cotcot]

Thanks for your reply nm.
The -fps 25 -noskip option seems to improve the frame rate dropping problem only a little bit. The framerate is stable during the first 10 minutes. Same for deleting harddup. I am going to capture the vhs in chunks of 10 minutes.
The sound remains bad. So i will have to record sound separately from video and put them together afterwards.