Extend duration of ambient audio track when converting 60fps to 30fps

[BG Davis]

Hello, all,

Can't seem to find a way to extend the duration of ambient audio track to match the increased length of 1/2 speed video (60fps input rendered as 30fps output).  As a result the ambient audio quits halfway through the new slow motion video.

What would be the correct configuration for the audio?  The only filter frame rate changes allowed are Film to PAL or PAL to Film; nothing about ~60 to ~30 or half speed or double the duration. 

Video input was AVCHD 1080/60p, audio input was ACC (Panasonic GX7).

I have audio output set to MP3 (lame).  Video output set to Mpeg4 AVC (x264).  Video results are awesome but only the first half has audio.

Thanks!

[mean]

Simplest would be to extract the audio track and manipulate it with audacity or similar then reimport it

[BG Davis]

Thank you!
Pity there's no way to "stretch" the ambient sound within Avidemux.