add movie link for popcorn

README.md

@@ -14,7 +14,7 @@ you have that much more time to do even more things!
 
 Name|Description 
 ---|---
-[popcorn](apps/popcorn)| This is a movie player for 30fps 320x240 movies with 44100 stereo sound, read in a custom format from SD card... it can even play backwards :-) TODO: add a link to big buck bunny in the right format TODO: add converter
+[popcorn](apps/popcorn)| This is a movie player for 30fps 320x240 movies with 44100 stereo sound, read in a custom format from SD card... it can even play backwards :-) Sample movie file linked from [here](apps/popcorn/README.md).
 [usb_sound_card](apps/usb_sound_card)| A no frills but functional USB sound card... hooked up via our old (pre TinyUSB) USB device stack. Keeping it around as it works nicely!
 
 ## Audio

apps/popcorn/README.md

@@ -0,0 +1,24 @@
+This is a 320x240x30 movie player that runs at a 48Mhz system clock (it was developed on FPGA which ran at that frequency).
+
+The compression format is not surprisingly not crazily advanced, so movie files are large!
+
+### Sample Movie
+
+Here is "Big Buck Bunny": https://drive.google.com/file/d/1q3szTVccPZ08v_TMDxy9ZgqeOOXXwHCX/view?usp=sharing which is 1.6GB
+
+### Using a movie
+
+These are raw disk images without a filesystem. These instructions assume a certain level of knowledge Please feel free to submit PRs
+to improve them!
+
+#### Single Movie
+
+A single movie can just be burned as the entirety of the SD card (via `dd` on unix). Note this will overwrite everything on the card.
+
+#### One or More Movies
+
+You can format the card with a GPT and then image movies onto the partitions (the partitions must obviously be big enough). The partition name from the GPT is used as the title for the movie.
+
+### Converting
+
+TODO - will upload a converter and instructions soon.