hi,  I have tried to create matroska movie from h264 video, but output file size was always 5kB - regardless of input file. I have used following instruction: gst-launch-0.10.exe filesrc location=movie.h264 ! "video/x-h264,height=480,width=640,framerate=25/1" ! matroskamux ! filesink location="E:\output.mkv" I have also tried to decode my h264 video and create matroska from received raw video: gst-launch-0.10.exe filesrc location=movie.h264 ! "video/x-h264,height=480,width=640,framerate=25/1" ! ffdec_h264 ! matroskamux ! filesink location="E:\output.mkv" I have receiced output file, but I can't play it in mplayer, because (this is part of my mplayer log): (...) ==> Found video stream: 0 ID_VIDEO_ID=0 ds_fill_buffer: EOF reached (stream: video) LAVF_check: Matroska file format libavformat file format detected. [matroska @ 00B5D3B4]Read error at pos. 13 (0xd) LAVF_header: av_open_input_stream() failed demux_aac_probe, failed to detect an AAC stream WINSOCK2 uninit Exiting... (End of file) I don't know why I have this "error at pos. 13". I suppose that something is wrong with my command, but I can't find what. I've search through this list archive, but I didn't find anything helpful. Monika