T 1280/07 08-06-2010

1. The appeal is admissible.

2. Main request: clarity of claim 1 (Article 84 EPC 1973)

2.1 Article 84 EPC 1973 requires that the claims define the subject-matter for which patent protection is sought, and that they shall be clear. This signifies that "an independent claim within the meaning of Rule 29 EPC [1973] should explicitly specify all of the essential features needed to define the invention, and that the meaning of these features should be clear for the person skilled in the art from the wording of the claim alone", see the opinion of the Enlarged Board of Appeal G 1/04 (OJ EPO 2006, 334), point 6.2. It is also established case law that all features which are necessary for solving the technical problem with which the application is concerned have to be regarded as essential features (see Case Law of the Boards of Appeal of the European Patent Office, 5th edition 2006, II.B.1.1.3).

2.2 In the present case it is common ground that the invention as defined in the present amended claims is concerned with solving the technical problem of producing, in the context of an MPEG-like transport stream, a frame accurate, seamless splice in which differences in video buffer verifier (VBV) levels can be seamlessly accommodated (see for instance page 15, paragraph 2, of the description). In the application a "seamless splice" is explicitly defined as "a splice which results in a continuous, valid MPEG stream" (see page 1, lines 23 and 24). Hence claim 1 should explicitly specify the features of the invention which solve this technical problem disclosed in the application, and the meaning of these features should be clear from the wording of claim 1 alone.

2.3 A frame accurate seamless splice from a first information stream into a second information stream requires that, considered in display order, all the frames of the first stream up to and including the target out-frame (last frame) and all the frames starting from the target-in frame and the following frames of the second stream be included in the spliced stream. However, an MPEG-like transport stream (including B frames) is transmitted in a different "transmission order", where I- or P-frames which are not intended for display in the spliced stream are transmitted before the target out-frame (see the top and bottom drawings of figure 5 of the application).

2.4 The present application proposes a transition clip which comprises frames of both the first and second streams. This transition clip necessitates a change in the last frames of the original first stream and in the first frames of the original second stream. It is common ground that this transition clip is one of the essential features of the invention. Thus claim 1 should explicitly specify the frames which are included in the transition clip such that the splice is frame accurate and also specify how the transition clip is formed such that a seamless splice results.

2.5 If the concatenated combination of the first stream, the transition clip and the second stream is to form a seamless splice, the transition clip has to contain all those frames of the original first stream up to and including the target out-frame and all those frames including and following the target in-frame of the original second stream which are no longer contained in the new first and second streams, everything considered in display order. In the example of figures 5 and 6, the last frame to be displayed which is still transmitted in the first stream, is frame 13 (see page 17, lines 8 and 9 and page 21, lines 2 to 5). Thus frame 14 and the target out-frame 15 (also called exit frame) of the original first stream should be contained in the transition clip (see page 22, lines 18 to 21). Likewise if the first frame to be displayed and contained in the newly created second stream ("to-stream") is frame 25 (see page 18, lines 4 to 6), then frames 23 and 24 should also be contained in the transition clip. If these frames are not contained in the transition clip, they should be part of the second stream (as actually hinted at in the bottom drawing of figure 6). Although the display order should remain unchanged, the transmission order of the frames in the newly created spliced stream may be different, in particular because frames of the transition clip are re-encoded. Confusion in the definition of claim 1 has been created by referring to display order, transmission order - sometimes within the same feature - and first and second streams without clearly distinguishing between original and newly created transmission order.

2.6 Claim 1 specifies that the transition clip is formed from re-encoded frames which are determined by the step of re-encoding specified in claim 1 and from "encoded frames comprising in transmission order the next I-frame and all frames between the next I-frame and the following I-frame". From the application as a whole it is clear that the next I-frame (figure 6: 19) and the frames between the next I-frame and the following I-frame (figure 6: 25) are the encoded frames of the second transport stream which follow the re-encoded frames of the second transport stream. Since the claim uses the expression "comprising", other encoded frames of the second transport stream may be included in the transition clip as well. But in the given technical context the frames between the next I-frame (19) and the following I-frame (25) depend on whether the display order or the transmission order is being considered (see the top and bottom drawings of figure 6 of the application). Claim 1 specifies that the transmission order is being considered for the specified encoded frames. This is in contrast to the step of re-encoding "some of said decoded frames" specified in claim 1, namely all decoded frames of the first transport stream following the actual transition out-frame up to and including the target out-frame and the decoded target in-frame and the following decoded frames up to the next I-frame of the second transport stream, in which the display order is being considered. The actual transition out-frame is defined in claim 1 as the frame immediately preceding the anchor frame preceding the target out-frame in transmission order (if the target out-frame is a B-frame), which anchor frame is frame 16 according to the example of figure 5 (the actual transition out-frame (12) being the frame after which the first stream is left; see also pages 20 and 21, bridging paragraph). Frame 13 in this example follows the actual transition out-frame (12) in display order and would thus have to be re-encoded according to claim 1, but is not contained in the transition clip according to the description (see page 17, lines 8 and 9 and page 21, lines 1 to 5).

2.7 When the (original) transmission order is being considered for the encoded frames and the display order is being considered for the re-encoded frames, some of the encoded frames may be the same frames as frames which have been re-encoded. Furthermore, depending on the manner of re-encoding, the re-encoded frames in the transition clip may have a transmission order different from the transmission order in the original streams. In the example of figure 6 of the application, for instance, the "next I-frame" is frame 19 and the "following I-frame" is frame 25. Since the (original) transmission order is being considered (bottom drawing of figure 6), frames 17 and 18 are between the next I-frame and the following I-frame. Frames 17 and 18, however, are also included in the transition clip as decoded and re-encoded frames (see the top drawing of figure 6). On the other hand frames 23 and 24 in the original transmission order (see bottom drawing of figure 6) are not between frame 19 and frame 25 and hence are not included in the transition clip specified in claim 1 even though they should be present in the resulting spliced transport stream if frame 25 constitutes the "first frame to be displayed from the to-stream" as stated in the description, page 18, lines 4 to 6. Although from the overall disclosure it may be assumed that copied frames in the transition clip and the new second stream may be transmitted in the original transmission order since the frame types remain the same, nothing is said about the transmission order of the re-encoded frames in the transition clip, except that the transition clip may be encoded as a closed GOP structure, that is a self-contained video clip (see page 22, lines 25 to 27).

2.8 Since the expression "encoded frames comprising in transmission order" covers the possibility that one and the same frame is present in a transition clip both as a re-encoded frame and as one of the frames forming part of the encoded frames, the transition clip is not clearly defined and the claimed method over its whole range would not result in a frame accurate splice. Hence claim 1 does not make clear which frames are included in the transition clip.

In this context the board has taken note of the appellant's argument that frames 17 and 18 were re-encoded frames and therefore did not form part of the encoded frames set out in claim 1. This argument does, however, not resolve the above ambiguity since claim 1 specifies "encoded frames comprising in transmission order the next I-frame and all frames between the next I-frame and the following I-frame" (emphasis by the board). Furthermore the appellant's argument that the frames of the transition clip were independent of whether display order or transmission order was being considered is not reflected in the definition of the transition clip given in claim 1 and does not resolve the confusion created in the definition of the claimed subject-matter as set out in point 2.5 above.

2.9 The appellant's argument that the person skilled in the art would understand from the description which frames were included in the transition clip did not convince the board. First, claim 1 itself should make clear which frames are included in the transition clip (see point 2.3 above). Second, in the present case the transition clip is described in the context of a specific embodiment having GOPs of a specific structure in the original streams. The description does not give a general definition or even explanation of the transition clip for GOPs of different original structure. Furthermore the description also comprises errors and inconsistencies in particular in those parts which describe the transition clip in the context of the specific embodiment.

2.10 In addition to the lack of clarity as to which frames are included in the transition clip, there is also a lack of clarity as to the technical meaning and effect of the "encoded frames" which are included in the transition clip. In the context of the technical problem underlying the invention (see point 2.2 above) the mere presence of these encoded frames in the transition clip does not have a technical function or effect that can be understood from the description, since the difference in VBV levels is accommodated by responsively adapting the re-encoding. It is not clear how the copied encoded frames can contribute to an adjustment of the VBV levels. Therefore their technical meaning in the context of claim 1 does not help in deciding which frames have to be included and which have not. In this context the appellant has argued that the temporal reference fields were restamped in order to achieve a seamless splice when the transition clip was put in transmission order. However claim 1 does not specify a restamping of temporal reference fields. The appellant has also argued that the presence of these encoded frames allowed for a smoothing of the transition resulting from the reordering of the frames in transmission order. However the appellant did not specify which parameter was smoothed by the reordering, nor does the description disclose how smoothing can be achieved by merely copying encoded frames.

The appellant's argument that there was no requirement in the EPC that every feature in a claim have a technical effect did not convince the board in the context of the objection raised against claim 1. The transmission clip is necessary for solving the technical problem with which the application is concerned and is thus an essential feature of the invention (see points 2.1 to 2.4 above). In particular the transmission clip is formed from re-encoded frames and encoded frames. Thus the technical meaning of both the re-encoded frames and the encoded frames in the context of the technical problem with which the application is concerned must be clear from the wording of claim 1 alone.

2.11 In view of the above the board judges that claim 1 according to the main request is not clear (Article 84 EPC 1973).

3. Auxiliary request: clarity of claim 1 (Article 84 EPC 1973)

The objection as to lack of clarity raised in point 2.10 above applies to claim 1 according to the auxiliary request as well. More specifically, claim 1 according to the auxiliary request specifies that the transition clip is formed from the re-encoded frames and the "encoded frames consisting of in transmission order the next I-frame and all frames which occur in display order after the next I-frame and occur in transmission order before the following I-frame". Hence the encoded frames are selected from the second transport stream so as to comply with two different conditions. Nevertheless the technical meaning of this selection is not clear from claim 1. If it is assumed that the original transmission order in the second stream is maintained in the first part of the spliced stream (i.e. the order as shown in the bottom drawing of figure 6: 25, 23, 24, 28), then the first frame to be displayed, which is transmitted in the second stream, would be frame 23 contrary to what is stated in the description (see page 18, lines 4 to 6). The description does not provide support which could serve as guidance as to how the copied frames have to be selected since it does not set out how the inclusion of these frames contribute to an adjustment of the VBV levels. Moreover, the mere selection of frames specified in claim 1 of the auxiliary request does not result in a seamless splice. As discussed in the context of the main request, the appellant has argued that the temporal reference fields were restamped in order to achieve a seamless splice when the transition clip was put in transmission order. However claim 1 of the auxiliary request does not specify a restamping of temporal reference fields. Hence the board judges that claim 1 according to the auxiliary request is not clear (Article 84 EPC 1973).

4. Under these circumstances the decision under appeal cannot be set aside and the appeal must be dismissed. Furthermore there is no need to decide whether the application meets the other provisions of the EPC referred to in the reasons for refusing the application given in the decision under appeal.