mkv to avi - audio out of sync problem

[HitcherUK]

Following on from my previous thread I thought I'd found the perfect answer for converting 720p mkv files to HR avi files while keeping 5.1 sound in SUPER.
All the samples I tried came out great at 960x544 resolution with AC3 sound so I converted a batch of episodes but when I watched one the other day the audio gradually went out of sync until it was about ½/sec out at the end.

At first I thought I'd used the wrong framerate but upon checking both input and output files were 23.976.

Any help appreciated.

[guns1inger]

What was the codec used in the mkv ? Not everything correctly reads the framerate from AVC encoded mkv files. If the video starts in sync and drifts out over time, generally it means that the framerates have not matched correctly. Open the two videos in mediainfo and check the running times of both video and audio, and see if any of them differ.

[HitcherUK]

Input file info -

General #0
Complete name        : E:\Downloads\x264\3x04 - The Frank Factor.mkv
Format               : Matroska
File size            : 550 MiB
PlayTime             : 20mn 17s
Bit rate             : 3793 Kbps
Encoded date         : UTC 2007-10-12 03:23:44
Writing application  : mkvmerge v2.0.2 ('You're My Flame') built on Sep 20 2007 09:25:45
Writing library      : libebml v0.7.7 + libmatroska v0.8.1

Video #0
Codec                : MPEG-4 AVC
Codec/Info           : MPEG4 ISO advanced profile
PlayTime             : 20mn 15s
Width                : 1280 pixels
Height               : 720 pixels
Aspect ratio         : 16/9
Frame rate           : 23.976 fps
Language             : English

Audio #0
Codec                : AC3
Codec/Info           : Dolby AC3
Channel(s)           : 6 channels
Sampling rate        : 48 KHz

Output file info -

General #0
Complete name        : E:\Downloads\3x04 - The Frank Factor.avi
Format               : AVI
Format/Info          : Audio Video Interleave
Format/Family        : RIFF
File size            : 349 MiB
PlayTime             : 20mn 15s
Bit rate             : 2401 Kbps
Director             : created.with.SUPER(C).v2007.bld.23
Writing application  : SUPER(C) by eRightSoft

Video #0
Codec                : XviD
Codec/Family         : MPEG-4
Codec/Info           : XviD project
Codec settings/Packe : No
Codec settings/BVOP  : No
Codec settings/QPel  : No
Codec settings/GMC   : 0
Codec settings/Matri : Default
PlayTime             : 20mn 17s
Bit rate             : 2004 Kbps
Width                : 960 pixels
Height               : 528 pixels
Aspect ratio         : 16/9
Frame rate           : 23.976 fps
Resolution           : 8 bits
Chroma               : 4:2:0
Interlacement        : Progressive
Bits/(Pixel*Frame)   : 0.158
Writing library      : SUPER(C)

Audio #0
Codec                : AC3
PlayTime             : 20mn 15s
Bit rate             : 384 Kbps
Bit rate mode        : CBR

[HitcherUK]

Is there a way of converting the original 720p mkv to a lower resulotion mkv? Maybe XBMC will be able to play it then?

[HitcherUK]

By the way I'm using the following output settings -

Output Container - AVI
Output Video Codec - MPEG-4 (XVID rendered file optimizer)
Output Audio Codec - AC3
MEncoder