Step 1: Log in as root

We're not going to dick around with sudo in this tutorial, so set your root password and log in as root.
Then, update for kicks.

cubie@Cubian:~$ sudo passwd root
Enter new UNIX password: 
Retype new UNIX password: 
passwd: password updated successfully
cubie@Cubian:~$ exit
Cubian login: root
Password:
root@Cubian:~# apt-get update
root@Cubian:~# apt-get upgrade

Step 2: Write stuff in config files

Since MPV isn't part of Debian Wheezy, first add the Debian Jessie repo to /etc/apt/sources.list. 

root@Cubian:~# cd /etc/apt
root@Cubian:/etc/apt# nano sources.list

On the bottom of the page add the following line

deb http://http.us.debian.org/debian jessie main

Now press ctrl + x
It will ask if you want to save. Press y.
It will ask what filename to use. Press enter. Now update atp-get again.

root@Cubian:/etc/apt# apt-get update


Change the amount of memory dedicated to the VPU from 80 megabytes to 256 megabytes.

root@Cubian:/etc/apt# cd /boot/
root@Cubian:/boot# nano uEnv.txt

The last line of uEnv.txt should start with "extraargs=". Add

sunxi_ve_mem_reserve=256

to the file. Save it. By default the VPU only has access to 80 megs of memory. Now it has access to 256.

Change some user permissions for video and audio

root@Cubian:/boot# cd /lib/udev/rules.d
root@Cubian:/lib/udev/rules.d# nano 90-sunxi-disp-permission.rules 

Add the following lines

KERNEL=="disp", MODE="0777", GROUP="video"
KERNEL=="cedar_dev", MODE="0777", GROUP="video" 
KERNEL=="g2d", MODE="0777", GROUP="video"

Save and exit nano. Now add the default user "cubie" to the some needed groups.
Alternatively if you have a different user prepared for this, use that.

root@Cubian:/lib/udev/rules.d# usermod -G sudo,video,audio cubie


Enable the sunxi VDPAU driver and it's experiment OSD support.

root@Cubian:/lib/udev/rules.d# cd /etc/
root@Cubian:/etc# nano environment

Add these lines:

VDPAU_DRIVER=sunxi
VDPAU_OSD=1

Step 3: Install stuff

Use apt-get to grab almost everything you need.

root@Cubian:/etc# apt-get install xorg build-essential git libvdpau-dev mpv

Once that finishes use git to get the latest source for the video driver and then compile the drivers.

root@Cubian:/etc# cd ~
root@Cubian:~# git clone https://github.com/linux-sunxi/libvdpau-sunxi.git
root@Cubian:~# cd libvdpau-sunxi
root@Cubian:~/libvdpau-sunxi# make
root@Cubian:~/libvdpau-sunxi# make install

Step 4: More configuration and Testing

All the necessary software should be installed at this point. 
Let's throw some basic configuration at MPV.

root@Cubian:~/libvdpau-sunxi# cd /etc/mpv
root@Cubian:/etc/mpv# nano mpv.conf

Add these lines:

vo=vdpau
hwdec=vdpau
hwdec-codecs=all
ao=alsa:device=[hw:1,0], pulse
slang=en,
fs=yes
force-rgba-osd-rendering=yes

Reboot.

root@Cubian:/etc/mpv# reboot

Now we're ready to test MPV with your favorite video file.
Login as cubie or whoever you usermodded above.
Then try playing a video file.

cubie@Cubian:~$ cd ~/yourmoviesfolder
cubie@Cubian:~/yourmoviesfolder$ startx -e "mpv yourvideofile.mkv"