After spending what feels like nearly a week, I've successfully got the Pi decoding to RGBA instead of YV12. This was a lot harder than it sounds because I had to add on a hardware "resizer" to the hardware "decoder". It is the resizer which is doing the colorspace conversion from YV12 to RGBA. Getting these two to interact with each other was quite tricky despite having example source code to refer to. But it's all working now so the next step is to add support for RGBA surfaces to my existing GLES2 code and then modify my LDImage code also work with RGBA surfaces in addition to the YUV444 surfaces that it already supports. Finally, I need to copy the pi's reference EGL code into the dexter code to make my GLES2 code work on the pi.
And then... video should work!