[FFmpeg-devel] Fixpoint FFT optimization, with MDCT and IMDCT wrappers for audio optimization

Mike . giac2000
Mon Aug 13 04:22:43 CEST 2007

Let me try this again. >On Mon, Jul 30, 2007 at 10:33:16PM -0400, Marc Hoffman wrote:> I will do it if it makes sense right now I don't see it being the most> efficient. Lets get through the basic acceptance and when you and I> decide to move forward we can talk about more efficient mechanisms for> general machines. (I'm not going anywhere so even if you accept this> we can change it in the future).>> The split radix is not the most efficient way to do things on the> BlackFin machine. It has to do with all the extra pointer stuff you> need to maintain. On other machines this is more efficient. Not to> go into this too much anyways I agreed earlier to implement this for> us (ffmpeg-devel) and I will just not right now. I really want to see> if I/we can get one audio codec to work in fixEDpoint and achieve high> quality I think this is what you/we really care about anyways.Marc,  I've implemented a the ffmpeg wma decoder in fixed point while you were discussing this.  Sadly I didn't see your mailings until now.  The code is a huge mess, but quite functional on several portable mp3 players.  I converted the MDCT/FFT to fixed point in a very similar way as above, and got very good results (typically 15 bits identical to the fp version) and good playback (needs about 40MHz on my iPod).  Please feel free to take a look at my code:http://svn.rockbox.org/viewvc.cgi/trunk/apps/codecs/libwma/?pathrev=14307Though once again, the code is extremely messy, and I'm still tracking down a handful of remaining bugs.__
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