Issue with audio sync on longer movies

[vistal]

Hello,
I have been experiencing an issue where when I stream longer movies the audio seems to get more and more out of sync as the movie goes on. Pausing/Seeking doesn't seem to fix it. I have noticed, however, that if I load a movie up and immediately seek to very far forward in the movie the audio is synced properly. I can only assume this is some sort of issue with transcoding?

My video transcoding is settings are from the recommended settings, but I will include them below:

Name:
flv/h264 video

Convert From:
avi mpg mpeg mp4 m4v mkv mov wmv ogv divx m2ts

Convert to:
flv

Step 1:
ffmpeg -ss %o -i %s -async 1 -b %bk -s %wx%h -ar 44100 -ac 2 -v 0 -f flv -vcodec libx264 -preset superfast -threads 0 -

I'm aware that converting these to a different video format is a possibility, but I have a very large collection with many different types of video (avi, mkv, mpeg, mp4 etc) and would prefer to avoid this. I have also checked my performance when these issues occur and I'm not even close to pushing my CPU or otherwise stressing the server.

Any help or suggestions that could be provided would be greatly appreciated.

[vistal]

Just thought I would add that I'm running Subsonic 4.9 on Centos6 in case it helps.