Here is the analysis of the board (emphasis added by the board):
Determining the closest prior artNote for the practice: If you argue that a certain document is not the closest prior art, be sure to know which one you think is closer.
3. The first step of the problem and solution approach is to determine the closest prior art, i.e. the most promising starting point - or the most promising springboard to the invention - for the assessment of inventive step. The jurisprudence of the boards of appeal has established criteria for identifying the closest prior art, see CLBoA, section I.D.3, with an emphasis on the following two:
(a) As a first criterion, the closest prior art should be related to the claimed invention, in the sense that it should disclose subject-matter conceived for the same purpose or aiming at the same objective, corresponding to a similar use, or relating to the same or a similar technical problem or, at least to the same or a closely related technical field.
(b) As a second criterion, the closest prior art should disclose subject-matter having the greatest number of relevant technical features in common with the claimed invention, i.e. requiring the minimum of structural and functional modifications.
3.1 In the present case, the subject-matter of claim 1 of the main request concerns a video processing method for decoding a bitstream according to the AVS standard. The claimed method provides an improvement over a conventional AVS decoding in that it allows the decoding of bitstreams coded according to different versions of the AVS standard (see section 2 above).
3.2 D1 is an article describing the main technical features of the AVS standard for coding and decoding video signals. The AVS standard is described in the present application as the starting point for the invention (see paragraphs  to  of the application as filed). D1 thus belongs to the same technical field as the claimed invention, i.e. the coding and decoding of video signals according to the AVS standard. It also serves a similar purpose and implicitly or explicitly addresses similar or the same technical problems as the claimed invention, i.e. those solved by the use of the AVS standard, such as a highly efficient video coding/decoding and an optimisation between absolute coding performance and complexity of implementation (see the INTRODUCTION section on the first page of D1). Moreover, the video processing method disclosed in D1 has several technical features in common with the method of claim 1, these features being essentially implied by the reference to the AVS standard in claim 1.
3.3 The appellant disputed that D1 could be regarded as the closest prior art, because it did not disclose the problem arising from the existence of different versions of the AVS standard (see paragraph  of the application as filed).
3.4 The board concurs with the appellant that D1 does not disclose this further problem, but disagrees that it should disqualify D1 as starting point for the assessment of inventive step. Indeed, the closest prior art need not disclose all the problems solved by the claimed invention, in particular it need not disclose the objective technical problem, which is only determined in the second step of the problem and solution approach based on the technical effect(s) provided by those features distinguishing the invention as claimed from the closest prior art.
3.5 In the present case, there is no other prior art on file which discloses the objective technical problem or which would qualify better than D1 as the closest prior art. During the oral proceedings, when asked by the board which prior art was the closest prior art if not D1, the appellant replied that there was none. The board cannot agree with this view. According to Article 56 EPC an invention is to be considered to involve an inventive step if, "having regard to the state of the art", it is not obvious to the skilled person. Hence, the assessment of inventive step has to be based on an evaluation of the invention in view of the prior art. The expression "closest prior art" also does not mean that it must be sufficiently close to the claimed invention on an absolute basis, but only that it must be relatively closer to the claimed invention than the other prior-art disclosures, i.e. it is selected as the most promising starting point - or the most promising springboard towards the invention.
3.6 The appellant further argued that, according to the established jurisprudence of the boards of appeal, it was essential that the (objective) technical problem be at least suggested in the closest prior art, in order to avoid an inadmissible ex post facto analysis. It referred to CLBoA, section I.D.6 and several decisions cited therein.
3.7 The board disagrees with the appellant's interpretation of the jurisprudence in section I.D.6 of the CLBoA. This section does not refer specifically to determining the closest prior art (dealt with in CLBoA, I.D.3), but generally to the interpretation of prior-art documents, which should not be influenced by the problem solved by the invention, where the problem is neither mentioned nor suggested in these documents.
When applied to D1, this jurisprudence means that the interpretation of D1 should not be influenced by a problem solved by the invention, but neither disclosed nor suggested by D1, which in the present case is a problem arising from the existence of different versions of the AVS standard (see point 3.3 supra). However, it does not mean, as argued by the appellant, that this problem should at least be suggested in D1 in order to avoid an inadmissible ex post facto analysis (see point 3.6 supra). The board's interpretation of D1 under point 3.2 supra is based on the disclosure of D1, without any reference to or influence by the above problem relating to different versions of the AVS standard.
Hence, the appellant's arguments under point 3.6 supra are not persuasive and the board's interpretation of D1 complies with the jurisprudence in CLBoA,
3.8 The appellant further submitted that the established jurisprudence of the boards of appeal required that the objective technical problem be related to the actual disclosure of the closest prior art. The appellant referred to CLBoA, I.D.3.3 and specifically to decisions T 835/00, T 686/91 and T 1898/07 cited therein.
3.9 The board is not convinced by these arguments for the following reasons.
According to the above three decisions, a prior-art disclosure not mentioning a technical problem which is at least related to that derivable from the patent specification under examination does not normally qualify as the closest prior art, however many technical features it may have in common with the claimed subject-matter (see T 686/91, point 4 of the Reasons, T 835/00, point 4.2 of the Reasons, and T 1898/07, point 45 of the Reasons).
In each of decisions T 686/91 (see point 4 of the Reasons), T 835/00 (see section 4.4 of the Reasons) and T 1898/07 (see points 46 to 48 of the Reasons), the board considered that the prior-art document which had the greatest number of features in common with the claimed subject-matter solved a technical problem unrelated to the problem solved by the claimed invention. For this reason, the board concluded in each of these decisions that the closest prior art, i.e. the most promising springboard towards the invention, was another prior-art document which had fewer features in common with the claimed subject-matter but solved a problem more closely related to that of the claimed invention.
In other words, in each of these three decisions the board considered that in those particular cases, although the afore-mentioned second criterion (greatest number of features in common) was met, the afore-mentioned first criterion was clearly not met, because the solved problem was unrelated to that of the invention. Hence, the board considered that, overall, that prior art was less suitable as closest prior art for assessing inventive step than other available prior art.
3.10 In the present appeal case, the situation is different from that of decisions T 835/00, T 686/91 and T 1898/07 in several aspects:
(a) D1 does not solve an unrelated problem. As explained above, it relates to the same technical field as the present application, which implies that it addresses problems related to video encoding using the AVS standard. Hence, there is no problem solved by D1 which is unrelated to a problem solved by the claimed invention.
(b) The application as filed describes the AVS standard as the starting point of the invention. D1 is essentially a prior-art document providing an overview of the AVS standard. D1 is thus essentially the same prior art as the one used by the appellant (and presumably also by the inventors) as the starting point for the claimed invention. It is thus surprising that the appellant argued that document D1 was not a suitable starting point for the assessment of inventive step.
(c) The reasoning in decisions T 835/00, T 686/91 and T 1898/07 is based on the underlying principle that the closest prior art should be the most promising springboard towards the invention (see T 835/00, point 4.1 of the Reasons). This is clearly the case for D1. Moreover, the appellant could not point to more suitable prior art; instead, it merely stated that in the present case there was no closest prior art.
Hence, the board is not convinced by the appellant's arguments that only with hindsight can D1 be regarded as the closest prior art.
3.11 In view of the above, the board considers that D1 meets the requirements established by the jurisprudence for being regarded as the closest prior art.
Point 3.4 hints to a discussion which is sometimes more problematic: Inventions sometimes solve a whole plethora problems (to render the apparatus cheaper, better, fancier or simply more beautiful) and these may depend on the starting point chosen and vice versa. The choice of the "subjective" problem is decisive for the "objective technical" problem and plays an important role not only in relation to inventive step (Art. 56 EPC) but also in relation to infringement by equivalent means.
Posted by Michael Thesen