T 1280/07 () of 8.6.2010

Summary of Facts and Submissions

I. The appeal is against the decision of the examining division to refuse European patent application No. 99 307 392.3.

II. The reasons for the decision under appeal referred to Article 84 EPC 1973, Article 123(2) EPC, Article 83 EPC 1973, and Article 56 EPC 1973.

III. The applicant appealed and filed with the statement of grounds of appeal inter alia new claims upon which the appeal was based.

IV. The board issued a communication pursuant to Article 15(1) of the Rules of Procedure of the Boards of Appeal (RPBA) annexed to a summons to oral proceedings and dated 9 March 2010. In this communication the board inter alia expressed doubts that objections under Article 123(2) EPC and Article 84 EPC 1973 raised in the decision under appeal had been overcome with the claims filed with the statement of grounds of appeal.

V. With a letter dated 6 May 2010 the appellant filed replacement claims and arguments.

VI. Oral proceedings before the board were held on 8 June 2010. During the oral proceedings the appellant filed claims 1 to 9 of a main request and of an auxiliary request, respectively. The appellant requested that the decision under appeal be set aside and that a patent be granted on the basis of claims 1 to 9 of the main request and, auxiliarily, of the auxiliary request, both submitted in the oral proceedings before the board. At the end of the oral proceedings the chairman announced the board's decision.

VII. Claim 1 of the main request reads as follows.

"A method for concatenating first (from) and second (to) MPEG-like transport streams to produce a spliced transport stream, comprising the steps of:

parsing (1010) a transport layer of each of said first transport stream and said second transport stream to identify packets associated with at least one of sequence headers, picture headers and predefined splicing syntax;

determining (1020), for each frame in each of said first transport stream and said second transport stream, a picture coding type, at least one of a picture number, a start of frame transport packet number, an end of frame transport packet number, a presentation time stamp (PTS) and a decode time stamp (DTS);

determining (805), for said first transport stream, a target out-frame representing a last frame of said first transport stream to be included in said spliced transport stream;

determining (905), for said second transport stream, a target in-frame representing a first frame of said second transport stream to be included in said spliced transport stream;

decompression decoding (710) when considered in display order, all frames of said first transport stream from and including the I frame preceding said target out frame up to and including said target out frame together with any other frame from which any of said all frames depend;

decompression decoding (715) when considered in display order said target in-frame of said second transport stream and all subsequent non-I frames thereof occurring before the next I-frame together with any other frame from which said target-in-frame and said all subsequent non-I frames depend;

re-encoding (720) some of said decoded frames of said first and second transport streams, said some decoded frames being all decoded frames following, in display order, the actual transition out frame of the first stream up to and including the target out frame, wherein in the case that said target out-frame is a B-frame, the said actual transition out frame is the frame immediately preceding the anchor frame preceding said target out-frame in transmission order; and in the case that said out-frame is not a B-frame, the said actual transition out frame is the frame immediately preceding, in transmission order, said target out-frame, and the target in-frame and the following frames in display order up to the next I-frame of the second transport stream,

forming a transition clip from said re-encoded frames and encoded frames comprising in transmission order the next I-frame and all frames between the next I-frame and the following I-frame; and

wherein the re-encoding is responsively adapted to the difference in VBV levels between the from-stream and the to-stream;

transport encoding the said transition clip, and

concatenating, in the order named, the said first transport stream up to the actual transition out frame thereof, said transport encoded transition clip and the said second transport stream following a transition in-frame thereof, said transition in-frame being said following I-frame and being the first frame of the second transport stream to be transmitted."

VIII. Claim 1 of the auxiliary request has the same wording as claim 1 of the main request except that the feature of forming a transition clip reads as follows.

"forming a transition clip from said re-encoded frames and 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; and"

IX. The reasons for the decision under appeal can be summarised as follows.

According to the description, the invention concerned frame accurate, seamless splicing. The scope of the claims, however, did not cover the case of frame accurate splicing. Some frames were included both before the transition clip and within the transition clip. Furthermore some frames were included both within the transition clip and after the transition clip. Therefore the claims were not supported by the description, contrary to Article 84 EPC 1973, and also contravened Article 123(2) EPC. In the description, the last frame of the first transport stream to be transmitted was the target out-frame. Thus the transition out-frame was the target out-frame. Using different terms for the same technical feature introduced a lack of clarity. As a consequence some frames were included twice in the spliced stream. Moreover, since the application as such did not allow executing the alleged invention of frame accurate, seamless splicing, the requirements of Article 83 EPC 1973 were not fulfilled either. Furthermore the description and figure 8 of the application together contained so many errors or contradictions that the examining division was of the opinion that some of the objections could not be repaired.

X. The appellant's arguments which are applicable to the present amended claims can be summarised as follows.

The specification did not disclose the apparent double transmission of frames identified by the examining division. The target out-frame was the final frame of the first transport stream which was going to be included in the spliced stream. The actual transition out-frame was the last frame of the first transport stream to be displayed as such. It was not included in the transition clip. All subsequent frames (in display order) following the actual transition out-frame from the first transport stream up to and including the target out-frame were included in the transition clip. The transition clip also included all frames (in display order) starting from and including the target in-frame of the second transport stream up to and not including the first frame of the second transport stream to be transmitted directly therefrom.

The objective technical problem addressed by the present invention was to produce, in the context of a transport stream, a frame accurate, seamless splice in which differences in video buffer verifier (VBV) levels could be seamlessly accommodated. The invention addressed this problem by defining a transition clip which was a combination of re-encoded and encoded frames and which was of a length allowing the VBV levels to be adjusted. The transition clip bridged the splice point. It comprised the last frames of the first transport stream and the first frames of the second transport stream, and the frames of the transition clip were managed together as a unit. In particular, the invention re-encoded the last frames of the first transport stream together with the first frames of the second transport stream to form a single group of pictures (GOP). When these frames were re-encoded together the VBV level could be adjusted from the first frame of the transition clip to the last frame of the re-encoded frames. There were a number of errors and inconsistencies in the description as to which frames were included in the transition clip, but a person skilled in the art would nevertheless be able to understand which frames were included in the transition clip and how the re-encoding allowed the VBV level to be adjusted. Those frames of the second transport stream which were not re-encoded but merely copied as encoded frames to the transition clip formed a second GOP of the transition clip. This second GOP was included in the transition clip in order to allow restamping of the temporal reference fields. This restamping was required because of the rearrangement of the frames of the transition clip when the transition clip was put in transmission order. Putting the transition clip in transmission order did not change the definition of which frames were included in the transition clip. The invention was very flexible because it always allowed the creation of a valid spliced transport stream even though the structure of the first GOP was not known beforehand. With some structures of the first GOP the second GOP was necessary to create a continuous valid spliced transport stream. With other structures it was not necessary, but the second GOP never prevented the creation of a continuous valid spliced transport stream.

There was no requirement that every feature in a claim have a technical effect. Hence it was not necessary that the second GOP in the transition clip have a technical effect. Furthermore a technical effect of the second GOP would have to be considered when comparing the claimed invention with the prior art, not when assessing whether the claim was clear.

Reasons for the Decision

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.

ORDER

For these reasons it is decided that:

The appeal is dismissed.