With Debian Jessie and KDEnlive 0.9.8-1 (updated from version ? before), I got this error message when I tried to create a proxy clip:

Code: Select all

avconv version 9.8-6:9.8-2+b2, Copyright (c) 2000-2013 the Libav developers
  built on Oct  9 2013 06:17:24 with gcc 4.8 (Debian 4.8.1-10)
-deinterlace is deprecated, use -filter:v yadif instead

I couldn´t find anyone else with this problem, and finally solved the problem myself. Hope this post helps others having the same problem.

Solution:
Change the proxy encoding parameters via "Settings > Configure KDEnlive > Project Defaults > Proxy Clips"
- replace "-deinterlace" with "-filter:v yadif"
- replace "libmp3lame-ac" with "libmp3lame" to prevent another error "Unknown encoder 'libmp3lame-ac'"