I also had this issue, and converted the video to Matroska and it solved this issue; actually, most of the time I create my videos using Blender, and found MKV works best, so I don't actually convert them, but I did test this on two videos that I converted using Hand Brake and avconv (didn't test it with ffmpeg, but I am sure it would work also), from AVI to MKV, and another one from MP4 to MKV and they worked fine.
I do remember talk about an option to use avconv instead of FFMPEG, its in a configuration file from what I remember, looking at other threads, I found the conversation between ToK and Sergio Costas; an exert is below:
In /usr/lib/devede/devede_ffmpeg_convert.py near line 231 I can switch
from ffmpeg to avconv by removing the # in front of the line:
changing
#command_var=["ffmpeg"]
command_var=["avconv"]
Now the rest of the conversation talked (below) about the File Format being an issue; but I found that MKV format fixed this issue for me.
Yes, but the problem is the file itself: if has an AC3 audio stream in
stereo (which is fine), but a MP2 5.1 audio stream (which is wrong: mp2,
AFAIK, can have only two channels).
To show you this works; here is a link to my ISO and Video that I did using Ubuntu 12.04 and Devede (out of the box, no changes to them other then unchecked ffmpeg):
http://lightwizzard.com , you will find links to them in the body; and when I tried to use AVI or MP4, it did what you said, Audio Sync was not right and other issues; so it was an issue with the file format itself, and ffmpeg was an issue; avconv actually worked better, but I did not try to change to it, as stated above; I'm still running the stock version with only the one change I mentioned, which was to un-check ffmpeg.