> > Hi,all, > I have some questions to discuss with you: > 1)i used some sine wave whose frequencies are 997,1k,etc to encode with > lame mp3 encoder, but i found 997.mp3 is not as good as 1k.mp3. then i use > soundforge to check theirs decoding wav, and i found some errors in decoding > 997.wav, why?
Ths sounds like a bug. But the first thing to do before reporting such a bug is to decode the mp3 files with 'lame --decode'. A lot of decoders out there have bugs too. > 2)i have tried to encode without Psymodel, and i tested the result using > a sine wave, it sounds well and it's SNR is approx equal to the old. And i > also tried to encode music, they sounds well too, so i want to do fixed > point encoding without Psymodel, but whether does it do well for all music? > 3)And,you know that the results of subband systhesis are also greater > than 2^31or less than -2^31, and almost all data of the table enwindow[] is > divided by 2.384e-06, so, to lessen the results, i change 2.384e-06 to > 2.384e-04 first, and multipled win[4][36] with 1e2, the results can be > represent with int! But the precision is not enough, and the SNR of final > mp3 encoding with this method isn't as good as old. Before, i calc subband > systhesis using exponent+mantissa, but it runs slowly. How to maintain > precision and the results don't exceed int? What about your opinion? > > best regards > anne > You should be able to get pretty good results without the maskings from the psymodel, but you probably still need pre-echo detection and some default masking values. All the additional masking computations is probably only a 10-20% improvement. It's necessary if you want to compete on quality, but not necessary if you are just putting together an embedded app to sell to people who dont know any better :-) As for the precision problems, with carefull scaling (and you may have to rescale many times for different parts of the algorithm) I think you should be okay with 32 bit integers. But it will require a detailed understanding of every algorithm. I have no idea if commercial embedded encoders are using all integers, or software floating point - what ever they are doing it is probably a closely guarded secret! Mark _______________________________________________ mp3encoder mailing list [EMAIL PROTECTED] http://minnie.tuhs.org/mailman/listinfo/mp3encoder
