Public bug reported:

Hi friends. I'd like to share some findings. These have included the
17.10 repo version of MPV (v0.26) as well as a more recent PPA version
(v0.27). Behaviors have been the same between the two versions. This is
using VAAPI hardware acceleration. My processor is an i5-7200u. My
system is Ubuntu 17.10. I'm using the Wayland session.

mpv.conf:

gpu-context=wayland
hwdec=vaapi
vo=gpu
save-position-on-quit


The issue comes in when streaming certain videos online. I was finding some 
videos would work fine, yet others would present a lot of gray box-like 
artifacts, enough where visibility of the video was impossible. I began to pay 
more attention to the terminal output when launching mpv + youtube.com URL via 
CLI. After some searching about video codecs, I began to wonder if the issue 
was specific to VP9 videos.


jason@JasT470:~$ mpv https://www.youtube.com/watch?v=V54CEElTF_U
Driver 'opengl' has been replaced with 'gpu'!
Driver 'opengl' has been replaced with 'gpu'!
Resuming playback. This behavior can be disabled with --no-resume-playback.
Loading config 
'/home/jason/.config/mpv/watch_later/13BA6C9FE6A59BE339409C1DB84E3403'
Playing: https://www.youtube.com/watch?v=V54CEElTF_U
 (+) Video --vid=1 (*) (vp9 1920x1080 29.970fps)
 (+) Audio --aid=1 --alang=eng (*) 'DASH audio' (opus 2ch 48000Hz) (external)
AO: [pulse] 48000Hz stereo 2ch float
Using hardware decoding (vaapi).
VO: [gpu] 1920x1080 vaapi[nv12]
AV: 00:00:26 / 00:03:26 (12%) A-V:  0.000 Cache: 10s+23MB
Saving state.


The above resulted in video that looks like the attached image. At times the 
video would seemingly buffer enough and work, though most of the time it looked 
like that image. Even when it would clear up a little bit, any sort of seeking 
would instigate the gray to overtake the majority of the player window again. 
During this time I experienced no issues with audio when the video was playing.

After doing some digging and finding some discussion regarding folks
wanting to avoid VP9 (but not having much context as to why), a string
to pass in mpv.conf was provided as follows:

ytdl-format=bestvideo[vcodec!=?vp9]+bestaudio/best

After appending this to my mpv.conf, I re-ran the same video as I did
above.


jason@JasT470:~$ mpv https://www.youtube.com/watch?v=V54CEElTF_U
Driver 'opengl' has been replaced with 'gpu'!
Driver 'opengl' has been replaced with 'gpu'!
Resuming playback. This behavior can be disabled with --no-resume-playback.
Loading config 
'/home/jason/.config/mpv/watch_later/13BA6C9FE6A59BE339409C1DB84E3403'
Playing: https://www.youtube.com/watch?v=V54CEElTF_U
 (+) Video --vid=1 (*) (h264 1920x1080 29.970fps)
 (+) Audio --aid=1 --alang=eng (*) 'DASH audio' (opus 2ch 48000Hz) (external)
AO: [pulse] 48000Hz stereo 2ch float
Using hardware decoding (vaapi).
VO: [gpu] 1920x1080 vaapi[nv12]
AV: 00:00:07 / 00:03:26 (3%) A-V:  0.000 Cache: 10s+25MB
Saving state.


As you can see in this second output (yet sourcing the same YouTube video), 
h264 is used in place of VP9. In this case, I had no video artifacts 
whatsoever, leading me to suspect the issue may be isolated around the VP9 
codec.

Please let me know if I can be of any assistance with testing. Thank you
for your time!

** Affects: mpv (Ubuntu)
     Importance: Undecided
         Status: New

** Attachment added: "Screenshot from 2017-11-04 23-48-39.png"
   
https://bugs.launchpad.net/bugs/1730551/+attachment/5005094/+files/Screenshot%20from%202017-11-04%2023-48-39.png

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https://bugs.launchpad.net/bugs/1730551

Title:
  Issue streaming VP9 based videos with MPV in 17.10 with VAAPI hardware
  accel in Wayland session

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