> > I was naively thinking that determining the right intensity > > position for > > each subband could also be a problem. > > No, this value is completely determined by the signal. It's an expensive > computation, but it's not complicated.
How do you determine the position? My idea would be (assuming you know that your sfb could be encoded with is) to compute power of left channel for a given sfb, compute the right power, and to divide left power by right power. According to the result, you could have a good idea about the is position. This doesn't seems so much expensive. Do you use something else? > Hmmm... I hadn't thought of trying to guess the threshold from the signal. > The idea clearly has merit; after all, that's how mid/side works. I was > just planning to check post facto, i.e. apply each level of intensity, and > see if it's an improvement or not. (Which is how Layer-I,II do joint.) You do encoding for each configuration? Well, this method is more likely to give you the best results, but it's sure it will be very very slow. Perhaps (in a given sfb) the following could work: Compute the average left and right power. Now, compute the ratio between left and right power. This will be our reference. Now, let's do a loop over each frequency band of this sfb. For each freq, compute the ratio between left and right. Compute the number of freqs that have a ratio that is more than 10% away of the average ratio. If less than 15% of freqs in this sfb are too far away (more than 10%) of the average ratio, then this sfb is qualified for is. Of course 10 and 15% are arbitrary and need to be determined by experiment. > Also, the concept of intensity is based on high-frequency signals not > needing stereo information. You'd probably want to do some research to see > whether similarity of shapes was actually relevant, and, if not, how low in > frequency you can progress before it is. Yes, you're right for very high sfbs. In sfb21 (as an exemple), it's very likely to be noise-like, and the left and right shapes are likely to be decorrelated. But I think my upper idea could be of use. Perhaps only in a given sfb range? _______________________________________________ mp3encoder mailing list [EMAIL PROTECTED] http://minnie.tuhs.org/mailman/listinfo/mp3encoder
