T 2407/19 17-08-2023

1. The appeal is admissible.

Main request and auxiliary request 1 - entitlement to the earlier claimed priority (Article 87(1) EPC)

2. As established by the Enlarged Board of Appeal in its opinion G 2/98 (OJ EPO 2001, 413) and confirmed in its decision G 1/15 (OJ EPO 2017, 82), the sole substantive condition laid down by the EPC (and the Paris Convention) for the right of priority to be validly claimed is that the priority document and the subsequent filing are directed to the same invention (Article 87(1) EPC). Article 4C(4) of the Paris Convention mentions "the same subject". However, the meaning is identical (see G 1/15, point 4.2 of the Reasons).

The requirement for claiming priority of "the same invention", referred to in Article 87(1) EPC, means that priority of a previous application in respect of a claim in a European patent application in accordance with Article 88 EPC is to be acknowledged only if the skilled person can derive the subject-matter of the claim directly and unambiguously, using common general knowledge, from the previous application as a whole (see G 2/98, Conclusion of the Opinion).

Moreover, the "same invention" must be disclosed in an enabling manner in the priority document (see G 1/15, Order of the decision).

3. In the case in hand, the examining division held that priority from the earlier application was not validly claimed for the subject-matter of all the claims of the main request and auxiliary request 1 because the following features in those claims were not disclosed in the earlier application (see section 1 of the Reasons for the decision):

"in order: the first context adaptive portion; the second context adaptive portion; the second bypass portion; and the first bypass portion, the second context adaptive portion and the second bypass portion being consecutively included"

4. The appellant has not disputed this finding.

5. The board concurs with the examining division that priority from the earlier application is not validly claimed for the subject-matter of all the claims of the main request and auxiliary request 1.

Main request and auxiliary request 1 - status of documents D4 and D5

6. Documents D4 and D5 were made available to the public after the filing date of the earlier application but before the filing date of the application at issue. Since the appellant is not entitled to the right of priority for the claimed subject-matter, these documents belong to the state of the art under Article 54(2) EPC.

7. The appellant has not disputed that documents D4 and D5 belong to the state of the art under Article 54(2) EPC.

Main request - inventive step (Articles 52(1) and 56 EPC)

8. Closest prior art and distinguishing features

8.1 It is common ground between the examining division and the appellant that either document D4 or document D5 may be regarded as the closest prior art and that each discloses all the features of the image coding method of claim 1 except the following distinguishing features:

(a) The second bypass portion is prior to the first bypass portion.

(b) The second context adaptive portion and second bypass portion are consecutively included.

(See points 2.1.1 and 2.2.1 of the Reasons for the decision under appeal, point IV.2, first paragraph, of the statement of grounds of appeal and Section III, first paragraph, of the appellant's letter of 7 August 2023.)

8.2 The board concurs with this finding.

9. Technical effect

9.1 Preliminary considerations

The relevant aspects of the coding in the method of claim 1 may be summarised as follows:

First binary data indicating a first intra prediction mode comprises two portions: a first context adaptive portion (hereinafter also referred to as "prefix_1") and a first bypass portion (hereinafter also referred to as "suffix_1").

Second binary data indicating a second intra prediction mode comprises two portions: a second context adaptive portion (hereinafter also referred to as "prefix_2") and a second bypass portion (hereinafter also referred to as "suffix_2").

Prefix_1 and prefix_2 are coded by context adaptive binary arithmetic coding (CABAC).

Suffix_1 and suffix_2 are coded by bypass coding.

In claim 1, coded data is generated which includes the prefixes and suffixes in the following order:

prefix_1, prefix_2, suffix_2, suffix_1 (distinguishing feature (a)),

wherein prefix_2 and suffix_2 are "consecutively included" (distinguishing feature (b)).

In contrast, in the closest prior art (D4 or D5), the coded data is generated in the following order:

prefix_1, prefix_2, suffix_1, suffix_2.

9.2 It is undisputed that a technical effect achieved by the method of claim 1 arises from the feature that suffix_1 and suffix_2 are next to each other in the coded data. According to the description of the application as filed, this feature makes it possible to perform the bypass coding on these two suffixes in parallel (see, for instance, paragraph [0056]).

However, it is also undisputed that the same technical effect is achieved by the same feature in documents D4 and D5 (see, for instance, Abstract and Introduction of D4 and Conclusion of D5). Hence this technical effect does not count as a technical effect achieved over the closest prior art.

9.3 Appellant's arguments

According to the appellant's statement of grounds of appeal, the technical effect over the closest prior art (D4 or D5), i.e. arising from the distinguishing features, may be summarised as follows.

The order suffix_2, suffix_1 in claim 1 (distinguishing feature (a)) instead of suffix_1, suffix_2 in D4 and D5, together with the feature that prefix_2 and suffix_2 are consecutive (distinguishing feature (b)), decreased the "complexity of processing" (see point IV.3 of the statement of grounds of appeal).

The existence of this technical effect was supported by paragraphs [60], [76] and [214] of the application as filed, which mentioned a decrease in the degree of complexity. This decrease in complexity arose from the fact that, because prefix_2 and suffix_2 were consecutive, prefix_2 did not require temporary storing in a buffer until suffix_2 was decoded, as a result of which the memory requirements were reduced in the encoder/decoder (page 3, third paragraph, and page 6, second paragraph, of the statement of grounds of appeal). Regarding the reduction of memory requirements, the appellant referred to paragraph [109] of the application as filed, which mentioned that the "prefixes of the intra prediction modes are not temporarily stored".

9.4 The examining division's view

The above arguments from the appellant regarding the alleged technical effect, which were essentially already provided in the first-instance proceedings, did not convince the examining division for the following reasons (see point 2.1.3 of the Reasons for the decision under appeal).

(1) The application provided no explanation on how having contiguous prefix_2 and suffix_2 would actually lead to a decrease in processing complexity in coding or decoding.

(2) The disclosure of Figure 9 and paragraph [109] of the application as filed did not teach the skilled person that the claimed invention solved the problem of providing a syntax that was suitable for both decoders that aimed at increased parallelism and decoders that had limited memory, as argued by the applicant. This technical effect did not appear to be derivable from other passages of the description either and thus could not form a basis for the definition of the technical problem.

(3) The alleged technical effect was not obtained by any claimed steps or means with reduced complexity, nor was it apparent from the application as a whole how such technical effect would be enabled by the claimed features.

The examining division therefore concluded that there was no meaningful technical effect achieved by having the prefix_2 and suffix_2 consecutively included in the coded data (see point 2.1.4 of the Reasons for the decision under appeal).

Hence, distinguishing feature (a) simply corresponded to one of a set of arbitrary alternatives to the order disclosed in D4 or D5, and it was an order that the skilled person would have obviously considered according to the circumstances (see point 2.1.4 of the Reasons for the decision under appeal).

9.5 Further arguments by the appellant

In its letter of 7 August 2023 and during the oral proceedings before the board, the appellant further developed its arguments in the following directions.

(A1) The fact that prefix_2 and suffix_2 were "consecutively included" in the bitstream allowed the coder/decoder to immediately use the output of the processing of prefix_2 as an input for the processing of suffix_2, thereby reducing the complexity of processing and reducing the memory requirements in the coder/decoder, because said output could, for instance, be stored in a low-level register instead of having to be fetched from the main memory at a later time. Prefix_2 could even be used as an address to a table for the processing of suffix_2 and thus not be stored at all.

(A2) The reduction of memory requirements could be a reduction in the amount of time for which the memory was used rather than a reduction in the amount of memory used.

(A3) The distinguishing features created a bitstream which provided an advantage both when decoded by parallelism-enabled decoders (parallel processing of bypass portions) and when decoded by sequential decoders (reducing the memory requirements and decreasing the complexity of processing).

(A4) There was a synergy between distinguishing features (a) and (b) because it was the combination of both that, on the one hand, allowed parallel processing of bypass portions (suffixes) and, on the other hand, made it possible to reduce the memory requirements and decrease the complexity of processing.

(A5) Even if the board did not recognise that the distinguishing features achieved a technical effect of reducing memory requirements and/or decreasing processing complexity, the fact remained that the distinguishing features were not suggested by any prior-art documents on file.

9.6 The board's view

For the reasons set out below, the board is of the view that the technical effects alleged by the appellant, i.e. a reduction of memory requirements and a decreased complexity of processing in the encoder/decoder, are not achieved by the features of claim 1.

9.6.1 The application as filed briefly mentions a decreased complexity of processing in paragraphs [60], [76] and [214] and a reduction of memory requirements in paragraph [109]. However, as pointed out by the examining division, it does not provide any explanation why these technical effects are achieved.

Since there are many ways in which encoders and decoders could be designed, such as in hardware, software or a mix of the two, and claim 1 covers all of them, the alleged advantages would have to exist for substantially all of these forms of implementation.

9.6.2 Re arguments (A1) and (A2)

The board is not convinced that merely placing prefix_2 and suffix_2 consecutively in the bitstream is sufficient for achieving the effect that the "prefixes do not have to be temporarily stored (e.g., until the suffixes are decoded)" as stated on page 3, third paragraph, of the statement of grounds of appeal. Decoded prefix_2 may indeed have to be stored for less time than decoded prefix_1 (compared with the methods disclosed in documents D4 and D5), but it must still be stored until suffix_2 is decoded.

The board is not convinced by the argument (argument A1) that the decoded prefix_2 could be provided as an address of a table for the processing of suffix_2 and thus would not have to be stored, because it is based on features (an address of a table) which are not present in claim 1 and, in fact, not even in the application as a whole.

Hence the board cannot discern any reduction in the amount of memory being used.

The board is also not convinced as regards the alleged reduction of the time for which the outputs of prefix_1 and prefix_2 are stored. The reverse order of suffix_1 and suffix_2 compared with D4 or D5 does shorten the storage time of prefix_2; however, it correspondingly lengthens the storage time of prefix_1. The sum of storage times for prefix_1 and prefix_2 thus remains essentially unchanged.

The argument (argument A1) that a (fast) register may be used instead of a (slow) main memory for storing prefix_2 is based on the assumption that prefix_2 and suffix_2 would be processed continuously as one entity at a low hardware level. However, no such features are present in claim 1. This is not implied by the contiguity between prefix_2 and suffix_2 because a return to a higher syntactic level of processing may be necessary between the end of the processing of prefix_2 and the start of processing of suffix_2.

For the above reasons, on the basis of the features of claim 1, the board cannot discern either a reduction of memory requirements or a decrease in complexity of processing compared with the closest prior art. Hence arguments A1 and A2 are not persuasive.

9.6.3 Re arguments (A3) and (A4)

The technical effect of the parallel processing of the bypass portions (suffixes) is already achieved by the closest prior art (D4 or D5). It is achieved not by distinguishing features (a) and (b) but by the feature that suffix_1 and suffix_2 are next to each other in the coded data. It is thus not a technical effect achieved over the closest prior art.

The alleged technical effects of reducing memory requirements and decreasing complexity of processing are not achieved by the distinguishing features of claim 1 for the reasons given in point 9.6.2 above.

It thus also follows that there is no synergy between distinguishing features (a) and (b) in achieving these effects.

9.6.4 Re argument (A5)

The appellant is correct that none of the prior-art documents on file discloses the following sequence of coded data of claim 1:

prefix_1, prefix_2, suffix_2, suffix_1 (distinguishing feature (a)), wherein prefix_2 and suffix_2 are "consecutively included" (distinguishing feature (b)).

In the closest prior art (D4 or D5), the coded data is generated in the following order:

prefix_1, prefix_2, suffix_1, suffix_2.

However, since in the closest prior art suffix_1 and suffix_2 are processed in parallel, it would have been obvious to the skilled person that the order of these two suffixes does not matter. Hence, the skilled person would have regarded the order of the suffixes in claim 1 as an obvious alternative to the order of the suffixes in the closest prior art.

For the reasons given in point 9.6.2 above, the reverse order of suffix_1 and suffix_2 compared with the closest prior art does not achieve the technical effects (reduction of memory requirements and decrease of complexity of processing) alleged by the appellant.

That is not to say that no technical effect at all is achieved, because any change to the order of suffix_1 and suffix_2 will necessarily have an effect on the structure of the encoder/decoder. However, this technical effect will merely amount to the predictable technical advantages and disadvantages associated with such changes.

9.7 Obviousness

For the above reasons, the board concurs with the examining division that the distinguishing features of claim 1 are merely one of several obvious alternatives to D4 or D5 with predictable pros and cons.

In the absence of an unexpected and credible technical effect arising from the distinguishing features, the distinguishing features are to be regarded as one of several obvious alternative solutions having predictable pros and cons, and the prior art does not need to contain an incentive for the skilled person to select the particular solution claimed (see Case Law of the Boards of Appeal of the European Patent Office, 10th edition, 2022, "Case Law", I.D.9.21.1 and I.D.9.21.9).

10. Conclusion on inventive step

For the above reasons, the subject-matter of claim 1 of the main request does not involve an inventive step in view of the disclosure of either document D4 or document D5 (Articles 52(1) and 56 EPC).

11. Conclusion on the main request

Since the subject-matter of claim 1 does not involve an inventive step, the main request is not allowable.

Auxiliary request 1 - amendments

12. Claim 1 of auxiliary request 1 differs from claim 1 of the main request on account of the following additional feature:

"wherein the first intra prediction mode is used to predict luma of the image, and the second intra prediction mode is used to predict chroma of the image"

Auxiliary request 1 - inventive step (Articles 52(1) and 56 EPC)

13. The board concurs with the examining division that the skilled person, starting from the closest prior art (D4 or D5) and wishing to increase the amount of parallelism even further, would have obviously considered extending the teaching of D4 or D5 regarding the luma intra prediction mode to the chroma intra prediction mode, thereby arriving at the additional features of claim 1 without an inventive step (see point 3.5 of the decision under appeal).

14. The appellant argued that the skilled person would not have arrived at the additional features of claim 1 without an inventive step because it would have required an extra step of dividing the chroma intra prediction mode into a context adaptive portion and a bypass portion.

15. The board does not find this argument persuasive for the following reasons.

In the closest prior art (D4 or D5), the luma intra prediction mode is divided into a context adaptive portion and a bypass portion. The division of the chroma intra prediction mode into a context adaptive portion and a bypass portion would thus have been a straightforward consequence of the teaching concerning luma being applied to chroma.

16. Conclusion on inventive step

For the above reasons, the subject-matter of claim 1 of the main request does not involve an inventive step in view of the disclosure of either document D4 or D5 (Articles 52(1) and 56 EPC).

17. Conclusion on auxiliary request 1

18. Since the subject-matter of claim 1 does not involve an inventive step, auxiliary request 1 is not allowable.

Auxiliary request 2 - amendments

19. Claim 1 of auxiliary request 2 differs from claim 1 of auxiliary request 1 on account of the features underlined under point X. above.

Auxiliary request 2 - admittance (Article 13(2) RPBA 2020)

20. In the case in hand, the summons to oral proceedings was notified after the date on which RPBA 2020 entered into force, i.e. 1 January 2020 (Article 24(1) RPBA 2020). Thus, in accordance with Article 25(1) and (3) RPBA 2020, Article 13(2) RPBA 2020 applies to the question of whether to admit the amended claims according to the appellant's auxiliary request 2, which were filed after the summons to oral proceedings was notified. The amended claims of auxiliary request 2 are therefore amendments within the meaning of Article 13(2) RPBA 2020.

21. Article 13(2) RPBA 2020 reads as follows:

"Any amendment to a party's appeal case made after the expiry of a period specified by the Board in a communication under Rule 100, paragraph 2, EPC or, where such a communication is not issued, after notification of a summons to oral proceedings shall, in principle, not be taken into account unless there are exceptional circumstances, which have been justified with cogent reasons by the party concerned."

22. Article 13(2) RPBA 2020 implements the third level of the convergent approach applicable in appeal proceedings (see document CA/3/19, section VI, explanatory remarks on Article 13(2), first paragraph, first sentence; see also Supplementary publication 2, OJ EPO 2020). Article 13(2) RPBA 2020 imposes the most stringent limitations on appeal submissions which are made at an advanced stage of the proceedings, namely after expiry of a period set by the board of appeal in a communication under Rule 100(2) EPC or, where no such communication is issued, after notification of a summons to oral proceedings (see document CA/3/19, section VI, explanatory remarks on Article 13(2), first paragraph, second sentence). Where an amendment is made to a party's appeal case at this advanced stage of the proceedings, Article 13(2) RPBA 2020 provides that it will, in principle, no longer be taken into account unless the party concerned has shown compelling reasons why the circumstances are exceptional. If such circumstances are shown to exist, the board of appeal may, in exercising its discretion, decide to admit an amendment made to the appeal case at this advanced stage of the proceedings (see document CA/3/19, section VI, explanatory remarks on Article 13(2), third paragraph, last sentence).

23. In the case in hand, auxiliary request 2 was filed after notification of a summons to oral proceedings and in a letter of reply (dated 7 August 2023) to the board's communication pursuant to Article 15(1) RPBA 2020 expressing the board's preliminary opinion. In that letter, the appellant submitted that the claims of auxiliary request 2 were identical to the claims of auxiliary request 2 forming the basis of the decision under appeal. No reason was given for filing auxiliary request 2 at this late stage.

24. During the oral proceedings, the appellant gave the following reasons for the late filing of auxiliary request 2.

- The appellant had not maintained this request with the statement of grounds of appeal because it was convinced that the examining division was clearly wrong in its assessment of the main request and auxiliary request 1 and that the board would concur with the appellant on these requests. It thus appeared unnecessary to the appellant to maintain auxiliary request 2.

- It was only when the appellant received the board's preliminary opinion that it realised, with surprise, that the board was inclined to concur with the examining division regarding the main request and auxiliary request 1.

In response to the board's surprising preliminary opinion, the appellant decided to re-file auxiliary request 2.

25. The board is of the view that the above circumstances are not "exceptional circumstances" within the meaning of Article 13(2) RPBA 2020 for the reasons set out below.

25.1 The appellant should have been aware of the possibility that the board might concur with the examining division regarding the main request and auxiliary request 1.

If the appellant was interested in auxiliary request 2 as a fallback position, it should have maintained this request in the statement of grounds of appeal so that the board could provide a preliminary opinion on the merit of the reasons given in the decision under appeal for not allowing this request.

By filing this request at a late stage of the appeal proceedings (only ten days before the date of the oral proceedings), the appellant prevented the board from properly reviewing it.

The appellant's justification that it was convinced that the board would not concur with the examining division on the higher-ranked requests cannot be accepted as describing "exceptional circumstances" within the meaning of Article 13(2) RPBA 2020. If the board were to accept the appellant's justification as sufficient, the admittance of every new claim request filed in response to a board's preliminary opinion could be justified on that basis, which would deprive Article 13(2) RPBA 2020 of its purpose.

25.2 The board notes that the appellant did not argue that auxiliary request 2 had been filed as a reaction to new facts or evidence, or a new interpretation of claim 1, set out by the board in its preliminary opinion. The board's preliminary opinion was essentially in line with the reasons given by the examining division in the decision under appeal.

26. Conclusion on auxiliary request 2

For the above reasons, the board did not admit auxiliary request 2 into the appeal proceedings (Article 13(2) RPBA 2020).

Auxiliary request 3 - amendments

27. Claim 1 of auxiliary request 3 differs from claim 1 of auxiliary request 1 on account of the features underlined under point XI. above.

Auxiliary request 3 - admittance (Article 13(2) RPBA 2020)

28. Auxiliary request 3 was filed at a late stage of the oral proceedings before the board, after the board had expressed a negative opinion on the higher-ranked requests.

29. Auxiliary request 3 had not been submitted in first-instance proceedings and included additional features taken from the description.

30. According to the appellant, the "exceptional circumstances" were that it had understood for the first time during the oral proceedings why the board was of the view that the distinguishing features of claim 1 did not achieve the alleged technical effect(s). Auxiliary request 3 was filed in response to this.

31. The board did not find the appellant's above reasons persuasive because during the oral proceedings the board essentially maintained the same position as in its preliminary opinion on inventive step, which itself was essentially in line with the examining division's assessment of inventive step in the decision under appeal. Of course, the discussion during the oral proceedings allowed the board to express certain aspects of its position in more detail than in its written preliminary opinion. However, this is almost always the case at oral proceedings. Thus, if the board were to accept the appellant's justification as sufficient, the admittance of every new claim request filed at an advanced stage of the oral proceedings could be justified on that basis, which would deprive Article 13(2) RPBA 2020 of its purpose.

32. Conclusion on auxiliary request 3

For the above reasons, the board did not admit auxiliary request 3 into the appeal proceedings (Article 13(2) RPBA 2020).

Conclusion

33. Since the main request and auxiliary request 1 are not allowable and auxiliary requests 2 and 3 are not admitted into the appeal proceedings, the appeal must be dismissed.