I am trying to convert an mkv file to dvd. The mkv contain h264 video and 5.1 dts audio. I have used both FAVC and AVS2DVD but the result was the audio and video were out of sync. Trying to find the root of the problem, I used mkvextract to extract the audio from the mkv. Surprisingly, I found out that the extracted audio was shorter that the original mkv. Below is some information from MediaInfo:

Original mkv:
- MKV, Video duration is 1 hour 36 minute
- Audio duration is 1 hour 36 minute
- CBR 1510 kbps 5.1 DTS audio
- Audio stream size 1.01 GiB

Extracted audio:
- Audio duration is 1 hour 32 minute
- CBR 1510 kbps 5.1 DTS audio
- Audio stream size 995 MiB

With other mkv, the extracted audio was ok. They were the same duration and same stream size. Only that particular mkv that is giving me headache. There is no delay and stretch parameter set in the mkv. The mkv can be play ok in pc. Any idea what is causing the discrepancy between the extracted audio and the audio in the mkv?