I have found that -oac copy produces incorrect results in some particular cases. Here is a simple way to test the bug; take a dvd with LPCM audio and do: mencoder dvd://1 -ovc frameno -oac copy -aid 160 -frames 500 -o file.avi Now play file.avi: mplayer file.avi You will get only loud noise. Explanation of the bug: durning the copy mencoder stores in the avi header the format of the audio stream, the line of C code that does it in mencoder.c is: mux_a->wf->wFormatTag = sh_audio->format Now format, member of the structure sh_audio_t, is a unsigned int but wFormatTag, member of the structure WAVEFORMATEX, is a unsigned short. If the audio stream has a format that can be represented with 16 bit, the result is correct: 0x50 (mp2) 0x55 (mp3) 0x2000 (ac3) 0x1 (pcm) If the audio stream has a format that requires more than 16 bit, it cannot be stored correctly in the avi header. 0x10001 (dvdpcm) and all the other 32 bit format listed in codec.conf I have prepared this small patch: --- libmpdemux/ms_hdr.h.ori 2005-01-17 11:49:41.000000000 -0400 +++ libmpdemux/ms_hdr.h 2005-01-17 11:50:37.000000000 -0400 @@ -4,7 +4,7 @@ #ifndef _WAVEFORMATEX_ #define _WAVEFORMATEX_ typedef struct __attribute__((__packed__)) _WAVEFORMATEX { - unsigned short wFormatTag; + unsigned int wFormatTag; unsigned short nChannels; unsigned int nSamplesPerSec; unsigned int nAvgBytesPerSec; I did some tests and it seems to work. But I'm not sure if it breaks something else. Can anybody comment on this patch? I have found a similar structure defined in loader/wine/mmreg.h the following patch change wFormatTag as before, but I dont know if this should be appliend or not, may be it is not necessary. --- loader/wine/mmreg.h.ori 2005-01-17 12:30:33.000000000 -0400 +++ loader/wine/mmreg.h 2005-01-17 12:30:38.000000000 -0400 @@ -47,7 +47,7 @@ #ifndef _WAVEFORMATEX_ #define _WAVEFORMATEX_ typedef struct __attribute__((__packed__)) _WAVEFORMATEX { - WORD wFormatTag; + DWORD wFormatTag; WORD nChannels; DWORD nSamplesPerSec; DWORD nAvgBytesPerSec; I can prepare and submit a proprer patch if requested. Giacomo