----- Original Message ----- From: "Ivan Dimkovic" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, January 23, 2002 6:05 PM Subject: Re: [MP3 ENCODER] MS stereo
> Take a look at your 'factor' - this is called "bmax" or BMLD protection > ratio. If you find a BMLD formula you will notice that it depends on a > median bark value of the codec partition band: > > bmax[b] = pow(10, -3 * (0.5 + 0.5 * cos (PI * min(bark_val(b), > 15.5)/15.5))); (as described in ISO doc) > > Now, like I said - although ISO says that you should apply "imaging" every > time (mld = Mspreading-energy*bmax[b]), this is not exactly correct. You > should apply imaging if and only if L and R threshold difference is less > than some value (LAME uses 2 dB) - this is described in the Patent Number I > gave you. That's why I said that Imaging depends on the masking thresholds > and not the energy. "Imaging thresholds" are derrived out of energy values > and bmax[b] - which represents amount of stereo masking for that particular > band. > > Take a look at LAME code, it has very good (for MP3, that is) M/S > implementation and you can identify the parts you quoted in the psymodel.c > code. There are some additional issues that need to be solved - i.e. to > avoid constant toggling of M/S on and off (in MP3 that causes additional > artifacts), and to verify does the bit allocation yield in bitrate savings, > etc.. Is there any mechanism on avoiding the toggling effect in Lame. Also, what is the effect on the constantly toggle > Best Regards, > > ************************************************* > Ivan Dimkovic, Technical Manager > > PsyTEL Research > Multimedia Coding Solutions > Belgrade Yugoslavia > > phone: +381 63 264 334 > phone: +381 64 11 40 600 > fax: +381 11 32 25 275 > _______________________________________________ mp3encoder mailing list [EMAIL PROTECTED] http://minnie.tuhs.org/mailman/listinfo/mp3encoder
