it was reported in [1] that mplayer has issues playing newer video formats: I was able to reporduce the issue on a sample.mp4 video that uses vp9 video codec. Issue reported upstream at https://trac.mplayerhq.hu/ticket/2416 $ mplayer ./sample-vp9.mp4 MPlayer 1.5+svn38681-2+b1 (Debian)Can't open joystick device /dev/input/js0: No such file or directory Can't init input joystick mplayer: could not open config files /home/lorenz/.lircrc and /etc/lirc/lircrc mplayer: No such file or directory Failed to read LIRC config file ~/.lircrc. Playing ./sample-vp9.mp4. libavformat version 63.1.102 (external) libavformat file format detected. [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f8b97528f40]Protocol name not provided, cannot determine if input is local or a network protocol, buffers and access patterns cannot be configured optimally without knowing the protocol [lavf] stream 0: video (vp9), -vid 0 [lavf] stream 1: audio (aac), -aid 0, -alang und VIDEO: [vp09] 3840x1600 24bpp 25.000 fps 634.2 kbps (77.4 kbyte/s) ========================================================================== Cannot find codec matching selected -vo and video format 0x39307076. ========================================================================== Clip info: major_brand: isom minor_version: 512 compatible_brands: isomiso2mp41 encoder: Lavf62.12.102 Load subtitles in ./ ========================================================================== Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders libavcodec version 63.1.102 (external) AUDIO: 44100 Hz, 2 ch, floatle, 128.4 kbit/4.55% (ratio: 16050->352800) Selected audio codec: [ffaac] afm: ffmpeg (FFmpeg AAC (MPEG-2/MPEG-4 Audio)) ========================================================================== [AO OSS] audio_setup: Can't open audio device /dev/dsp: Device or resource busy [AO_ALSA] alsa-lib: pcm_dmix.c:1000:(snd_pcm_dmix_open) unable to open slave [AO_ALSA] Playback open error: Device or resource busy AO: [pulse] 44100Hz 2ch floatle (4 bytes per sample) Video: no video Starting playback... ========================================================================== Cannot find codec matching selected -vo and video format 0x39307076. ========================================================================== A: 0.0 (unknown) of 5.0 (05.0) ??,?% ========================================================================== Cannot find codec matching selected -vo and video format 0x39307076. ========================================================================== A: 0.0 (00.0) of 5.0 (05.0) ??,?% ========================================================================== Cannot find codec matching selected -vo and video format 0x39307076. ========================================================================== A: 0.0 (00.0) of 5.0 (05.0) ??,?% ========================================================================== Cannot find codec matching selected -vo and video format 0x39307076. ========================================================================== A: 0.1 (00.0) of 5.0 (05.0) ??,?% ========================================================================== Cannot find codec matching selected -vo and video format 0x39307076. ========================================================================== A: 0.1 (00.1) of 5.0 (05.0) ??,?% ========================================================================== Cannot find codec matching selected -vo and video format 0x39307076. ========================================================================== A: 0.2 (00.1) of 5.0 (05.0) ??,?% ========================================================================== Cannot find codec matching selected -vo and video format 0x39307076. ========================================================================== A: 0.2 (00.2) of 5.0 (05.0) 0.4% Too many key file descriptors, cannot register file descriptor 4. ========================================================================== Cannot find codec matching selected -vo and video format 0x39307076. ========================================================================== [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=939822#26