Informikon

I have mentioned that I started to write some Mpeg-1 decoding routines in C#. By now, I have an almost complete decoder written in C# from scratch (i.e. I just followed the spec. or the Standard document).

Since now I can play video segments with this code, I started measuring its performance. I knew it wasn't good but I hadn't done any profiling yet. I added some timing instructions and, my initial results, were something like: more than 11 secs for my decoder vs 0.09s for FFMpeg; or around 120 times slower. After further investigations, I found that more than 95% of the decoder execution time was spent in my "naive" implementation of the IDCT. So I've changed it to a simple but faster one (the Chen-Wang algorithm) and now the running time is within five times of FFMpeg.

I'm sure that there are plenty more opportunities for optimization in the original code, so my XMas Holidays asssignment will be to continue improving its speed. These observations certainly explain the considerable efforts done in improving the performance of this critical piece of video processing: the DCT/IDCT.