mencoder, convert mkv to avi + ac3. sound issues

[clavain]

Hello all,

I am trying to convert various .mkv files to smaller .avi files. I have settled on using mencoder, the video looks fine but there seems to be a problem with the audio.

The problem is that while the input and output both have 6 channel ac3 sound, when the output file is played in anything but mplayer only the background sounds can be heard none of the other channels are heard. If I change the audio options in VLC to stereo then the sound is fine so it is there and in mplayer everything sounds great.

Thanks in advance for any help, some more info on what I am doing is below:

I am using Windows XP SP2 with MEncoder 1.0rc2-4.2.1 using following command:

mencoder.exe input.mkv -ffourcc XVID -ovc lavc -lavcopts vcodec=mpeg4:threads=8:vbitrate=2000:cmp=2:subcmp=2:trell=yes:v4mv=yes:mbd=2 -vf scale=960:528 -oac lavc -lavcopts acodec=ac3:abitrate=384 -channels 6 -o output.avi

The output from a successfully encoded video is:

MEncoder 1.0rc2-4.2.1 (C) 2000-2007 MPlayer Team
CPU: Intel(R) Core(TM)2 CPU          6400  @ 2.13GHz (Family: 6, Model: 15, Stepping: 6)
CPUflags: Type: 6 MMX: 1 MMX2: 1 3DNow: 0 3DNow2: 0 SSE: 1 SSE2: 1
Compiled with runtime CPU detection.
success: format: 0  data: 0x0 - 0x22651c46
[mkv] Track ID 1: audio (A_AC3), -aid 0, -alang und
[mkv] Track ID 2: video (V_MPEG4/ISO/AVC), -vid 0
[mkv] Will play video track 2.
Matroska file format detected.
VIDEO:  [avc1]  1280x720  24bpp  23.976 fps    0.0 kbps ( 0.0 kbyte/s)
[V] filefmt:31  fourcc:0x31637661  size:1280x720  fps:23.98  ftime:=0.0417
==========================================================================
Opening audio decoder: [liba52] AC3 decoding with liba52
Using SSE optimized IMDCT transform
Using MMX optimized resampler
AUDIO: 48000 Hz, 6 ch, s16le, 384.0 kbit/8.33% (ratio: 48000->576000)
Selected audio codec: [a52] afm: liba52 (AC3-liba52)
==========================================================================
Opening video filter: [expand osd=1]
Expand: -1 x -1, -1 ; -1, osd: 1, aspect: 0.000000, round: 1
Opening video filter: [scale w=960 h=528]
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffh264] vfm: ffmpeg (FFmpeg H.264)
==========================================================================
Forcing output FourCC to 44495658 [XVID].
VDec: vo config request - 1280 x 720 (preferred colorspace: Planar YV12)
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 1.78:1 - prescaling to correct movie aspect.
SwScaler: reducing / aligning filtersize 7 -> 8
SwScaler: reducing / aligning filtersize 7 -> 8
SwScaler: reducing / aligning filtersize 7 -> 6
SwScaler: reducing / aligning filtersize 7 -> 6
[swscaler @ 00D24D00]SwScaler: BICUBIC scaler, from yuv420p to yuv420p using MMX 2
[swscaler @ 00D24D00]SwScaler: using 8-tap MMX scaler for horizontal luminance s caling
[swscaler @ 00D24D00]SwScaler: using 8-tap MMX scaler for horizontal chrominance scaling
[swscaler @ 00D24D00]SwScaler: using n-tap MMX scaler for vertical scaling (YV12 like)
[swscaler @ 00D24D00]SwScaler: 1280x720 -> 960x528
videocodec: libavcodec (960x528 fourcc=44495658 [XVID])
[VE_LAVC] High quality encoding selected (non-realtime)!
Writing header...
ODML: Aspect information not (yet?) available or unspecified, not writing vprp header.
Writing header...
ODML: Aspect information not (yet?) available or unspecified, not writing vprp header.
Pos:   0.0s      3f ( 0%)  0.00fps Trem:   0min   0mb  A-V:0.008 [0:0] 1 duplicate frame(s)!
Pos:   0.2s      5f ( 0%)  0.00fps Trem:   0min   0mb  A-V:0.014 [0:0] 1 duplicate frame(s)!
Pos:1266.9s  30376f (99%) 27.79fps Trem:   0min 360mb  A-V:0.041 [1999:383]
Flushing video frames.
Writing index...
Writing header...
ODML: Aspect information not (yet?) available or unspecified, not writing vprp header.

Video stream: 1999.332 kbit/s  (249916 B/s)  size: 316627331 bytes  1266.932 secs  30376 frames
Audio stream:  384.000 kbit/s  (47999 B/s)  size: 60816384 bytes  1267.008 secs

[45tripp]

The problem is that while the input and output both have 6 channel ac3 sound,

why re-encode then?
copy audio