Comment 4 for bug 1727210

I have the same problem - at least the same symptoms as the OP when playing MP4 viedos with totem on wayland.
My video card is an ATI HD5850 using the radeon driver.
The video will play in totem on xorg. It will also play on wayland with mpv or vlc.

The only warning I get from totem is:

(totem:7298): Gtk-WARNING **: Drawing a gadget with negative dimensions. Did you forget to allocate a size? (node slider owner GtkScale)

but I'm not sure if it is relevant.

vainfo output:

$ vainfo
libva info: VA-API version 0.40.0
libva info: va_getDriverName() returns 0
libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/r600_drv_video.so
libva info: Found init function __vaDriverInit_0_40
libva info: va_openDriver() returns 0
vainfo: VA-API version: 0.40 (libva )
vainfo: Driver version: mesa gallium vaapi
vainfo: Supported profile and entrypoints
      VAProfileMPEG2Simple : VAEntrypointVLD
      VAProfileMPEG2Main : VAEntrypointVLD
      VAProfileVC1Simple : VAEntrypointVLD
      VAProfileVC1Main : VAEntrypointVLD
      VAProfileVC1Advanced : VAEntrypointVLD
      VAProfileH264ConstrainedBaseline: VAEntrypointVLD
      VAProfileH264Main : VAEntrypointVLD
      VAProfileH264High : VAEntrypointVLD
      VAProfileNone : VAEntrypointVideoProc

As I prefer totem over the other players, my current workaround is to fallback to xorg.