I can obviously not say that either of us is right, only that I can understand that after reading this particular patent, one might have the idea that one could come up with a time-varying overlapped transform coder that is safe from this patent.

IIRC, on last AES conference in Amsterdam  Dolby presented  variable-length overlapped transform codec that uses MDCT (I think) - the purpose of this codec was to perfectly match the NTSC/PAL timing  frame-by-frame, which wasn't quite possible with today's codecs.  Perfect timing was needed because in case of cut/copy operations small "click" artifacts appeared due to discontinuities.

5853
Michael J. Smithers,Brett G, Crockett,Louis D. Fielder,
Two methods of coding and delivering ultra-high quality audio are presented. Both methods are video frame synchronous and editable at common video frame rates (23.98, 24, 25, 29.97 and 30 frames per second) without the use of sample rate converters. The first is an ultra-high quality audio coder that exceeds 4.8 on the ITU-R 5 point audio impairment scale at a data-rate of 256 kbps per channel and at up to three generations of encoding/decoding. The second is an enhanced method of video frame synchronous PCM packing. Specifically the problem of transmitting 48 kHz audio in 29.97 Hz frames is examined.
Ultra High Quality, Video Frame Synchronous Audio Coding

Doesn't Parseval's Theorem say that frequency domain energy is equal to time domain energy?

Even if Vorbis does the energy calculation in the frequency domain on a specific frequency band, there are ways to do the exact same in the time domain, making it a direct function of the amplitude changes. A frequency domain representation is just a different way of presenting the signal, it is still the same signal.

I find the statement "function of changes in signal amplitude" a bit strange. A signal itself is fully defined by it's amplitude changes, meaning that every method of using the signal for the switching is covered, unless you use just 1 sample  . Or am I missing something here?

I think it was:

Quote

5853
Michael J. Smithers,Brett G, Crockett,Louis D. Fielder,
Two methods of coding and delivering ultra-high quality audio are presented. Both methods are video frame synchronous and editable at common video frame rates (23.98, 24, 25, 29.97 and 30 frames per second) without the use of sample rate converters. The first is an ultra-high quality audio coder that exceeds 4.8 on the ITU-R 5 point audio impairment scale at a data-rate of 256 kbps per channel and at up to three generations of encoding/decoding. The second is an enhanced method of video frame synchronous PCM packing. Specifically the problem of transmitting 48 kHz audio in 29.97 Hz frames is examined.
Ultra High Quality, Video Frame Synchronous Audio Coding

But don't take my word for it 

I think we got into one very serous discussion right now,  because this patent is applicable to many other codecs, some of them - not that open

It would be very interesting for the audio coding society to see what is the real influence of this patent to MDCT window switched codecs - I think the best way would be to call Mr. Edler to participiate as he is the principal inventor of the window-switched filterbank.

If patent proves to be applicable to Vorbis/WMA/...  it will be quite problematic to avoid it in any further "free" codec.   Otherwise, it would be a clear sign that it is possible to write audio coding-decoding system that works in MDCT domain without infringing some of the "unavoidable" patents.

/* build the window : we ensure that when the windows overlap
       their squared sum is always 1 (MDCT reconstruction rule) */

    /* XXX: merge with output */
    {
        int i, next_block_len, block_len, prev_block_len, n;
        float *wptr;

        block_len = s->block_len;
        prev_block_len = 1 << s->prev_block_len_bits;
        next_block_len = 1 << s->next_block_len_bits;

        /* right part */
        wptr = window + block_len;
        if (block_len <= next_block_len) {
            for(i=0;i<block_len;i++)
                *wptr++ = s->windows[bsize];
        } else {
            /* overlap */
            n = (block_len / 2) - (next_block_len / 2);
            for(i=0;i<n;i++)
                *wptr++ = 1.0;
            for(i=0;i<next_block_len;i++)
                *wptr++ = s->windows[s->frame_len_bits - s->next_block_len_bits];
            for(i=0;i<n;i++)
                *wptr++ = 0.0;
        }

        /* left part */
        wptr = window + block_len;
        if (block_len <= prev_block_len) {
            for(i=0;i<block_len;i++)
                *--wptr = s->windows[bsize];
        } else {
            /* overlap */
            n = (block_len / 2) - (prev_block_len / 2);
            for(i=0;i<n;i++)
                *--wptr = 1.0;
            for(i=0;i<prev_block_len;i++)
                *--wptr = s->windows[s->frame_len_bits - s->prev_block_len_bits];
            for(i=0;i<n;i++)
                *--wptr = 0.0;
        }
    }

I dunno about the patent - will take some time to analyse it carefully, but the provided ffmpeg code that is claimed to decode WMA smells like a MDCT block-switched coder with overlapped sine windows (as it could be seen in the code).

Actually, I never tried that FFMPEG code, so I am not sure.  But considering the fact that MS announced plans to open WMV/WMA specifications, I am sure they probably reworked all of the code to avoid any legal problems they might have.

It is also funny how FFMPEG used some of the Vorbis code for decoding WMA streams

If they paid for licensing that patent on window-switching (or any other patent which they use), would that allow them to open up the specs?

The LSP-to-curve code? I wonder if MS patented the idea of floor coding in general or only a specific way of coding the masking curve. Again a question for Vorbis (and probably a patent) that they should consider (or have considered, in which case it would be nice to know about it).

Actually, I never tried that FFMPEG code, so I am not sure.  But considering the fact that MS announced plans to open WMV/WMA specifications, I am sure they probably reworked all of the code to avoid any legal problems they might have.

recently, the official ffmpeg homepage had been closed to protest against software patents. so, they might suffer from legal problems

e.g. if the complete technological details were publicly available more than 20 years ago, then this technology is patent free. If there was a patent before, it has now expired. If there was a (same, similar or encompassing) patent filed more recently, then it doesn't cover this technology.

Ivan Dimkovic
That is also interesting,  would be worth trying digging in all NTT and Microsoft patents regarding this, since they are the only companies dealing with VQ / floor coding.

2Bdecided
But this doesn't mean that there's no such thing as patent free.

If a respected developer/researcher like Ivan is not certain whether a single patent applies to Vorbis (Ivan, if I misinterpret your postings, please correct me), how can a company be expected to obtain a view on this? Should they just accept the claim?

You are right - I am not sure,  of course - I did not take claims from people from big companies for granted,  I looked at the patent - and I disclosed my thoughts here.

Unfortunately, as it looks to me - this patent is very hard to avoid,  and, like everyone else on this forum I guess, I would really like to see some kind of official Xiph explanation how they manage to avoid this patent in their code.

Quote

Actually, I never tried that FFMPEG code, so I am not sure.  But considering the fact that MS announced plans to open WMV/WMA specifications, I am sure they probably reworked all of the code to avoid any legal problems they might have.

recently, the official ffmpeg homepage had been closed to protest against software patents. so, they might suffer from legal problems.

After digging through the code for not very long, that task seems to be performed by _ve_envelope_search, which in turn calls on _ve_amp. The comment in front of _ve_amp says this:

/* fairly straight threshhold-by-band based until we find something
   that works better and isn't patented. */

Consider this like a pure technical question called:

How can you avoid US Patent #5,214,742 in a MDCT window-switched codec?

...

So - we are getting down to elementary technical level, ok?

I hope that we can get back to meaningful discussion which could have some scientific importance.

Quote

Consider this like a pure technical question called:

How can you avoid US Patent #5,214,742 in a MDCT window-switched codec?

...

So - we are getting down to elementary technical level, ok?

I hope that we can get back to meaningful discussion which could have some scientific importance.

The only technical answer to this question is in Monty's code (envelope.c pointed to by c_haese). Anything more (debating the exact meaning of the words in the patents) is not a technical/scientific discussion but rather a legal one, which I don't think can be answered (without just stating opinions) by anyone on HA (including me). That is, unless you're a patent attorney?