working around MP3 patents, what features do specific patents refer to Options

[bawjaws]

I've been reading some of the mp3 patents and it appears to me (as someone with no general legal experience, no deep knowledge of patents, or great understanding of the inner workings of mp3) that some of them could be worked around easily if you cared more about avoiding patents than you did about making full use of the specification. And since many of the patents are expiring already a workable patent-free subset may already, or soon, be possible even before the very final patent expires around 2017.

To give a simple example, one of the last patents to go (according to http://www.osnews.com/story/24954/US_Paten..._MPEG-2_H_264/) is US patent 5812672:

"Method for reducing data in the transmission and/or storage of digital signals of several dependent channels"
http://patft1.uspto.gov/netacgi/nph-Parser...tnumber=5812672

This seems to be a patent on the concept of switching between different joint stereo modes based on the audio content. So a simple workaround would be to only produce mono files. No stereo means no joint stereo, means no switching between joint stereo modes, means absolutely no possible infringement of this particular patent (and if your intended input or output format was mono in the first place, absolutely no loss in quality compared with patented methods). If similar could be done for each of the remaining 12 (according to the link above) patents then you could include such an encoder in F/free software, and distribute mp3s created with such an encoder in games or in streaming radio without paying any fees and have them decoded by any standard-compliant decoder.

Note that I think for the example above, you could easily have stereo files without infringing the patent as long as you only had one stereo mode per file but I went with the mono example because it makes the non-infringement clearer. Maybe you could be very sneaky and still switch modes as long as you did it in a very slightly different manner from that described in the patent and get some further improvment in quality as a result. For all I know, maybe lame already does this differently/better than the patent. But that's just icing on the cake. Having *anything* that produces compatible mp3 files, even at a cost of reduced quality or flexibility would be a start and be useful to *someone* since mp3 is generally used today for compatability reasons rather than because of its technical qualities.

I'd like to know if there has been any concerted effort by people who actually understand this stuff (on both the legal and technical side) to create a functioning mp3 encoder and/or decoder that works around all known patents. Is it possible? At what cost in functionality, quality, bitrate etc. If not, which particular patent(s) are the blockers which you can't possibly work around and without which you cannot have a compatible, non-ear-killing mp3 and when does the last of them expire?

(There's also the interesting sub-issue, which seems to apply to most modern lossy codecs, which is if your encoder is doing something incredibly clever (and/or patented) to decide when to switch between different encoding modes, but your decoder is dumb as a rock and simply does what the encoded file tells it to, does the patent for the encoder process have any impact on the decoder?)

I'm guessing the messed up nature of patents means no-one with an actual business to protect is going to want to risk this when there are feasible alternatives (e.g. pay the fees or use vorbis) but it seems like it might be an interesting intellectual excercise anyway and some free audio tools (e.g. Audacity) might include such a thing if the general consensus was that it was possible (just as some people would avoid Vorbis because "you can never be sure" about patents, but it hasn't stopped most reasonable people).

This post has been edited by bawjaws: Mar 16 2012, 13:29

[bawjaws]

So, now you've got the general idea, some patents in reverse order of expiry (last to expire listed first):

Patent: Method and apparatus for encoding digital signals employing bit allocation using combinations of different threshold models to achieve desired bit rates
http://patft1.uspto.gov/netacgi/nph-Parser...tnumber=6009399
My uninformed take: use of multiple psycho-acoustic models, choosing most appropriate one based on targetted bitrate
Workaround: use the cited prior art which uses a single psycho-acoustic model but simply moves it up and down linearly to use up the correct amount of bits

Patent: Process of low sampling rate digital encoding of audio signals
http://patft1.uspto.gov/netacgi/nph-Parser...tnumber=6185539
My uninformed take: seems like a tweak in MPEG 2 layer III that repurposes MPEG 1 layer III to use three lower sample rates which are half the original spec (24, 22 & 16 added to 48,44 & 32 Hz)
Workaround: don't use those lower sample rates

Patent: Method for reducing data in the transmission and/or storage of digital signals of several dependent channels
http://patft1.uspto.gov/netacgi/nph-Parser...tnumber=5812672
My uninformed take: discussed in the first post, switching between joint stereo modes based on audio content
Workaround: Use Mono, Dual Stereo or Mid-Side for the whole file

If those three workarounds stand up then you've brought patent free mp3 forward almost exactly two years from April 2017 to April 2015. Then it gets tricky:

Patent: Digital adaptive transformation coding method
My uninformed take: No idea
http://patft1.uspto.gov/netacgi/nph-Parser...tnumber=5742735
Workaround: No idea

But since it gets easier again in the next one, I'm hopeful someone who actually understands what that patent means will see an easy workaround too.

Patent: Method for determining the type of coding to be selected for coding at least two signals
My uninformed take: an automatic way to choose when intensity stereo would be a good idea
http://patft1.uspto.gov/netacgi/nph-Parser...tnumber=5736943
Workaround: don't use intensity stereo ever, or let the user specify whether to use it or not

Patent: Method of coding a plurality of audio signals
http://patft1.uspto.gov/netacgi/nph-Parser...tnumber=5701346
My uninformed take: for encoding multi-channel surround sound
Workaround: only support stereo

Patent: Process for transmitting and/or storing digital signals of multiple channels
http://patft1.uspto.gov/netacgi/nph-Parser...tnumber=5706309
My uninformed take: for encoding multi-channel surround or multiple audio tracks like DVD commentaries
Workaround: only support stereo

etc. You get the idea. 6 out of 7 of these seem laughably easy to workaround (as long as you're not trying to encode multi-channel audio), and there's only 12 in total. So I'm guessing either I'm totally wrong about patents or law or encoding or there's some real doozies hiding in there that make it irrelevant to workaround the easy ones. Maybe the one that I don't understand is that doozie, but can anyone say for sure?

This post has been edited by bawjaws: Mar 16 2012, 17:03

[saratoga]

Maybe the one that I don't understand is that doozie, but can anyone say for sure?

I think claims 1-3 are basically for the quantization and scale factor system used in mp3. I don't think you could work around that while retaining compatibility with the standard.

[Garf]

Maybe the one that I don't understand is that doozie, but can anyone say for sure?

I think claims 1-3 are basically for the quantization and scale factor system used in mp3. I don't think you could work around that while retaining compatibility with the standard.

Reading the claims, I don't think this is the case for (1), the analysis of the original poster is correct that this is just one way to handle the bitrate vs distortion issue. This should be workable around, pretty easily in fact.

(2) is trickier, I wouldn't want to make a judgement without a careful rereading of the MP3 format spec. Understanding why this talks about low bit-rates - and how the spec differs there, would help.

(3) is indeed patenting a whole load of methods for M/S switching - this can be worked around easily, maybe at the loss of some efficiency.

(4) USPTO 5,742,735 initially looks like a killer, but as far as I understand patent law the claims have to match up exactly. At some point it says: "in view of psycho-acoustic aspects, quantification noise is masked for that frequency group; and if available after the preceding step, any additional number of bits are assigned to the individual frequency groups in correspondence to the quantitized maximum value occurring in the particular frequency group." The latter part makes this, IMHO, easily avoidable.

I haven't looked at the others yet.