Need Help Converting few videos.

I am trying convert few mkv,avi,mp4 for ipod touch.
Problem i am having, is that i don't want sound quality to change.
Here what happend using Total video converter:

Source 1080p video with 256kbps sound bitrate.
When i set the audio bitrate to 256 in TVC( audio codec: Auto) and video bitrate to 600kbps.
When video is converted its audio bitrate is about 160 instead of 256.
So i change the audio codec to aac again same 160(something).
changed it to ac3 or mp3 it converts them to 256kbps but the itunes says it can't be played in ipod.

Next i used VLC to convert in settings i choose
Encapsulation : mp4/mov
video codec : h-264
video bitrate and frame rate : 800kbps and 24 fps
Keed orignal audio track: yes
audio codec : MPEG 4 audio (aac)

after video is converted its extension is ts or ps i don't remember correctly, so i changed it to mp4 and tried to put in ipod and itunes said it can be done.
Any solution

Here's what i want:
I want no change in audio quality (bitrate etc) as far as possible
video : resolution 480x320 and bitrate i wanna try 600,800,1000 and see which one is best viewed in ipod.
Am i doing something wrong?

Thanks in advance
 
avidemux is what you want

just select audio to 'copy' and in video select 'filter' and select crop/resize according to your need
 
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