Patent term calculation is complicated in the US because there are essentially two different systems and quite a few corner cases. Even with a list of patents, it can be tricky to determine when the patents are all expired. Since I am a computer programmer (and not a lawyer), I created a program to try and automate this. This paper discusses how patent term calculation works, and some results from a combination of hand and automatic term calculation for MP3, MPEG-2 and H.264.
US Patent Basics
Patents provide the owner of the patent with the right to exclude others from using, making and selling the patented invention (that is, if someone else makes, uses or sells the invention without permission, the patent owner can sue them). The goal of the patent system is to provide inventors an incentive to invent and publish their inventions. Whether and how well this works for software is subject to debate. There is debate if software in the US is patentable or not, but those are discussed elsewhere. Patents must be filed by no later than one year after the publication of a description of the invention (and putting implementing source code on a public website or ftp site counts as publication), otherwise they are invalid. Other restrictions on patents exist as well. After a certain period of time, the patents expire. Calculating when this happens is complicated because there are basically two systems, the first is the older one where patents lasted 17 years after the grant date, and the newer system where patents last 20 years after the earliest filing date. This will be explained more later.
The patent status of a particular standard can vary. For example, the Fortran 66 standard can almost certainly be implemented without infringing any patents, since the standard is so old that any essential patents have long since expired (improperly issued patents could exist so there is a low but non-zero probability of getting sued). On the other hand, MPEG-2 has many essential patents (according to MPEG-LA) so it cannot be implemented and used without either licensing the patents or infringing on them. For some standards, the patent owners have released their patent rights and allow anyone to implement the standard using the patents without infringement. An example of this is the Theora video compression standard where On2 has licensed their patents.
However, just because a specification can be implemented without infringing patents doesn’t mean that a particular implementation doesn’t infringe patents. To invent an example, say you make a Fortran 66 compiler that will take a MPEG-2 video, decode it and look for fortran code and compile that code. Despite the fact that you could make a Fortran 66 compiler without infringing any valid and unexpired patents, this bizarre implementation would infringe on any MPEG-2 patents.
Searching for US Patent and Trademark Office’s patent database will produce large numbers of patents for many queries. For example, searching for Class 375/240.16, which is Subject matter wherein a signal is produced which represents the spacial change of an image portion, produced 1066 patents. That is many more patents than I want to look at. Smarter searches could reduce this number based on other criteria such as filing date, but still most searches for patents will quickly return more patents than anyone can handle. Instead, I used the ITU’s and ISO’s patent databases and MPEG-LA’s and the companies own claims for patents on the standard. The ISO’s patent database misses patents that have successfully been sued over so it should not be relied upon. On the other hand, companies that claim that their patents cover a standard and then ask for licensing fees have a bias to try and claim that they own as many essential patents as possible. In my spot checks, it looks like some of the patents that companies are claiming cover the standard are essential, and some look like they only cover possible implementations of the standard. Because of this method of search, two types of errors exist, errors of including patents that are not required for implementing the standard and missing patents that are required for implementing the standard.
Determining Patent Term and Start
As stated before, there are two different patent terms. It used to be that US patent terms lasted 17 years from the grant date. After the Uruguay Round Agreements Act the term was switched to 20 years (plus any term adjustments) from the first filing date. Patents that had already been filed get the longer of the 17 year or 20 year term (which ever term would make the patent expire last). Therefore determing the patent term requires determining the earliest filing date, determing whether a 17 year term could apply and if it could, finding the grant date. Finding the grant date is simple, it is on the patent. Finding the earliest filing date can get tricky however because of international patents, patent continuations, patent divisions and reissued patents. If the patent is from a Patent Cooperation Treaty (PCT), then the earliest filing date is when the PCT patent was filed. If the patent is a continuation or division of a previous patent, then the filing date is from the earliest continuation or division. If the patent is a reissed patent, then the earliest filing date on the original patent needs to be determined. The earliest filing date is also the one that counts for determining prior art. In the US, the prior art needs to have been available to the public one year before the earliest filing date. Determining whether a 17 year patent term could apply requires looking at the filing date and the PCT filing date. Patents filed before June 8, 1995 last the longer of 20 years from the filing date or 17 years from the grant date. If a patent is continued or divided, then the new filing date is the key one, not the earliest filing date (so a patent can loose the ability to have a 17 year term, though the earliest filing date stays the same). I think that if a PCT patent has a continuation or division, the date for determining if a 17 year patent is available will change, but I am not sure (see  and ). If the patent takes too long going through the patent office, a patent term adjustment can be added, which increases the 20 year term. Patents can expire early if the renewal fees are not payed.
Patent Term Calculation Examples
Simple one first: US 6009399.   Filed: 16 apr 1997 Granted: 28 dec 1999. No PCT, and no related US application data. It has no patent term adjustment. It is filed after June 8, 1995, so the term is just 20 years from the filing date, or 16 Apr 2017.
Two possible terms: US 4821260.   Filed: 16 dec 1987 Granted: 11 apr 1989. No PCT, and no related US application data. It has no patent term adjustment. It is filed before June 8, 1995, so term is longer of 17 years from grant date, or 20 years from filing date. 17 years from grant date is 11 Apr 2006, and 20 years from filing date is 16 Dec 2007, so expiration is 16 Dec 2007.
PCT Example: US 5706309.   Filed: 02 may 1995 Granted: 06 jan 1998. PCT Filed: 02 nov 1993. No related US Application data and no patent term adjustment. It is filed before June 8, 1995, so term longer of 17 years from grant date, or 20 years from earliest filing date. Since this is a PCT application, the earliest filing date is 2 Nov 1993, so the 20 year term is until 2 Nov 2013. The 17 year term ends on 6 Jan 2015, which is later so the the expiration is 6 Jan 2015.
Continuation Example: US 5321729.   Filed: 26 apr 1993 Granted: 14 jun 1994 Continuation of application Ser. No. 07/718,402, filed Jun. 24, 1991, now abandoned. No PCT, and no patent term adjustment. Since this is a continuation, the earliest file date is 24 Jun 1991, so the 20 year term ends on 24 Jun 2011. The 17 year term ends 14 Jun 2011, so the later of those is the expiration date of 24 June 2011.
Term Extension Example: US 7826532.   Filed: 03 mar 2005 Granted: 02 nov 2010 Division of of application Ser. No. 10/655,397 filed Sep. 5, 2003. No PCT. Patent term adjustment of 1546 days. Since this is a division, the earliest file date is 5 Sep 2003. The 20 year term should end on 5 Sep 2023, but because of the patent term adjustment of over 4 years, it instead expires on 29 Nov 2027.
Reissue Example: US RE39080.     Reissue of US 5627938. Filed: 22 sep 1994 Granted: 06 may 1997 Continuation of Ser. No. 07/292,598 filed Dec. 30, 1988 now
abandoned. No PCT. No Patent term adjustment. The 20 year term should end on 30 Dec 2008, but 5627938 was filed early enough that the 17 year term also applies, which would expire 06 May 2014, so the patent expires 6 May 2014.
Bonus example: US 5924060.   Filed: 20 mar 1997 Granted: 13 jul 1999. PCT filed: 29 Aug 1987. US 5924060 is a continuation of the abondoned PCT filing. If the PCT filing was able to grant a 17 year term, then this would expire in 13 Jul 2016. Based on my reading of the law, because the one filed with the PCT was abondoned, this instead expires at the end of the 20 year term which is 29 Aug 2007.
Automatic Term Calculation
In this report, most of the dates are calculated automatically with
the patent utilities that I wrote. They can be downloaded from
http://en.wikipedia.org/wiki/User:Jrincayc/Patent_utils . Note
that they are not perfect, since the data is not always stored in a
structured way. Unfortunately, since there are 230 plus patents in
the H.264 pool, it would be very time consuming to check all the
patents. On the other hand, if I did the calculations by hand, I would
invariably make mistakes by doing them manually. Take the conclusions
with a grain of salt. My previous calculations were wrong, and other MP3 term calculations I have found online have mistakes as well.
Maximum Patent Term
Because of the way that patent terms were calculated, before June 8, 1995, it was possible to make a patent quite a while after prior art via divisions, continuations and other tricks. After the 1995 date, some times a patent term extension can be granted. Without patent term extension and various tricks, the patents expire 20 years after filing, and the patent cannot be filed any later than 1 year after a publication, so 21 years after a specification is created, it starts becoming patent free. Taking into account the ability to do things like continuation before 1995, and adding in the approximately three years to get through the system plus 17 years after grant, an alternative date to be reasonably confident of being patent free is 1995+3+17+1 or 2016 for specifications published before 1995.
MPEG-1 ISO/IEC 11172
It is used for video cds and most DVD players can play these cds. MPEG-1 is a subset of
MPEG-2, so any complete MPEG-2 player can play MPEG-1 video and audio
as well. Both Microsoft Media Player
and Apple Quicktime play MPEG-1. There
are three different ways audio can be encoded in MPEG-1. The simplest
is layer 1,
layer 2 is more complicated and Layer 3 (also know as MP3) is the most
complex. A near
complete draft of MPEG-1 was created in September 1990 and the final
version of the decoding spec (ISO 11172-1,2,3) was published in
August 1993. The draft
standard was publicly available as
ISO CD 11172 by
December 6, 1991. Berkeley Plateau Multimedia Research Group created a
software MPEG-1 video decoder by November of 1992 (
Old versions download). Reference
encoders and decoders were published in 1998 by the
and the source code can be
The ISO has a patent database (Use the JCT1 one, and search for 11172) which lists one
patent owned by the Compusonics Corporation, US 4,472,747, which
expired in 2003. So,
is MPEG-1 be implemented without worrying about infringing patents?
Nope. This brings us to the next section of MPEG-1 Layer 3 audio or MP3.
at least three separate companies that claim to have patents,
their claimed US MP3 patents are listed in the automatically generated
MP3 patent list. The last of these patents expires in April of
2017. If you only look at the MP3 patents filed before December 1992
(one year after the decoding spec was published), then the last
decoding patent expires in September of 2015. AudioMPEG claims that
their patents cover MPEG-1 layers 1,2 and 3. The other companies just
talk about Layer 3. So, at the minimum, fully decoding and encoding
MPEG-1 audio is patented.
|Patent||Earliest File||Expiration Date|
An automatically generated patent expiration list is available at MP3 Patent list
An automatically generated patent expiration list is available at MPEG-2 Patent List. This list is generated from the MPEG-LA MPEG-2 list plus all the MP3 patents. MPEG-2 first came out in 1996. The last patent 7334248 expires in 2026, but it was first filed in 2002, so the initial MPEG-2 standard will count as prior art. Looking for patents that were filed in 1997 or before, 6181712 was filed in 1995, and does not expire until 2018, so 2018 might be a more reasonable date for MPEG-2 becoming patent free.
H.264 is a newer video codec. The standard first came out in 2003, but continues to evolve. An automatically generated patent expiration list is available at H.264 Patent List based on the MPEG-LA patent list. The last expiration is US 7826532 on 29 nov 2027 ( note that 7835443 is divisional, but the automated program missed that). US 7826532 was first filed in 05 sep 2003 and has an impressive 1546 day extension. It will be a while before H.264 is patent free.
The author Josh Cogliati is not a lawyer, so if you are basing your multimillionaire dollar business on this, you are a fool. I am also a human, so there are almost certainly errors in this. As well, these are my own opinions, not my employer’s. Starting 30 days after this is published, this may be distributed verbatim, or may be modified and or distributed under a Creative Commons Attribution 3.0 Unported License.