Hi, I have wrote simple script which (supposedly) could convert almost any video file into high-quality H264 MP4/AAC. Here it is: Dump both audio and video in raw format (because lavf cannot hadnle video streams with b-frames, and x264 can create only AVI, not MP4 container) mencoder $1 -ovc raw -nosound -o $1.temp.raw.avi mplayer $1 -vo null -ao pcm:file=$1.temp.wav Convert audio to AAC ffmpeg -i $1.temp.wav -acodec aac $1.temp.aac Here is the final stage, converting raw video into H264 while muxing it with AAC audio: mencoder $1.temp.raw.avi -audiofile $1.temp.aac -oac copy -of lavf -lavfopts format=mp4:i_certify_that_my_video_stream_does_not_use_b_frames -ovc x264 -x264encopts 4x4mv:subq=5:bframes=3:b_pyramid:weight_b -o $1.menc1p.mp4 Delete temp files. rm -f $1.temp.* However, I can play these on Linux (in VLC/Xine), on Mac VLC plays it without sound, While QuickTime Player and Windows Media Player cannot play them at all. Anyone could suggest what's wrong? Thanks in advance Andrei