avplay vp9.webm
where vp9.webm is some vp9 encoded webm
avplay version 9.18-6:9.18-0ubuntu0.14.04.1, Copyright (c) 2003-2014 the Libav developers
built on Mar 16 2015 13:19:10 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
[matroska,webm @ 0x7fb968005be0] Unknown/unsupported AVCodecID V_VP9.
[matroska,webm @ 0x7fb968005be0] max_analyze_duration reached
Input #0, matroska,webm, from 'vp9.webm':
Duration: 00:10:34.56, start: 0.000000, bitrate: N/A
Stream #0.0(eng): Video: [0][0][0][0] / 0x0000, 854x480, PAR 1:1 DAR 427:240, 30 fps, 30 tbr, 1k tbn (default)
vp9.webm: could not open codecs
1454077380.02 A-V: 0.000 s:0.0 aq= 0KB vq= 0KB sq= 0B f=0/0
avconv -codecs | grep libvpx
avconv version 9.18-6:9.18-0ubuntu0.14.04.1, Copyright (c) 2000-2014 the Libav developers
built on Mar 16 2015 13:19:10 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
DEV.L. vp8 On2 VP8 (decoders: vp8 libvpx ) (encoders: libvpx )
libvpx lost vp9.
I'm gonna leave it to rest until April 21st 2016 for planned Release Ubuntu 16.04 LTS