I’ve been struggling for quite a while now on the best way to implement a movie player for the NSpire calculator. nPlayer was also born around the same time and I realised there were other’s trying to do the same thing as I. I had to gain an edge over them. I immediately identified a few things I could improve in nPlayer. First, nPlayer was closed source and secondly, it didn’t have decent video compression. From there, I set out on my journey to create a good movie player for the NSpire.
The first version I made was a failure. It worked but took way too much storage. I recall it was in the tens of megabytes for just over a minute.
Since then, I have been looking for ways to reduce the amount of storage needed for a video file. I looked at using run length encoding but I realised that if the video didn’t have simply the same data repeated all the time (which is basically all the time), run length encoding would actually take more storage than if I hadn’t used it.
At one point, I looked at porting libmpeg to the NSpire. After several failed attempts, I finally had something that ‘probably’ works. But I realised the converting process is too complicated. The library needs a pure mpeg2 stream and thats not so easy to produce. Eventually I gave up on that.
Next, I took a look at using zLib to compress the frames. This, however, only reduced sizes by around 10 percent maximum and that’s still not good enough.
After a long break, I realised that with videos, a lossy compression was needed or else the size wouldn’t reduce by much. And so, I decided to look at motion jpeg. However, I wasn’t successful to get it working on the NSpire.
Finally, I compromised. I decided to give up on porting a real video codec while still using lossy compression. I remembered that jpeg files compress extremely well and I decided I could concatenate a whole series of jpeg files together into a single file and have them uncompress on the spot as it was being played.
All that’s left was to find a library that would decode jpeg files. I found a one-shot C library that did exactly that. I would feed it jpeg data and it would spit out a decoded frame.
All that’s left is to process the buffer and convert the colors and draw them out.
And voila, that is how Nspire Movie Player was born!