Summary
NEC Corporation filed a national phase patent application in India for a video coding device combining an adaptive colour transform technique with a chroma quantization offset to improve subjective image quality during video compression. The Assistant Controller of Patents and Designs refused the application under Section 15 of the Patents Act, 1970, finding the invention lacked inventive step over three prior art documents from HEVC screen content coding standards. The Delhi High Court dismissed NEC's appeal, holding that each key claimed feature was already taught or rendered obvious by the cited prior art documents, and that NEC had taken contradictory positions between the examination stage and the appeal. The ruling underscores that courts will hold applicants to positions taken before the Controller and will scrutinise standards-body publications as rigorous prior art in technology patent cases.
Background
NEC Corporation filed Patent Application No. 201717010986 before the Indian Patent Office in March 2017, a national phase entry from PCT Application PCT/JP2015/004037, claiming priority from a Japanese application of October 2014. The invention relates to a video coding device combining two techniques: adaptive colour transform in residual domain (choosing, per coding unit, whether to compress the prediction error in the RGB or YCoCr colour space) and a chroma quantization offset (adjusting quantization strength per colour component to improve subjective image quality). The technical problem NEC identified was this: when both techniques are used together, blocks in RGB space and blocks in YCoCr space share the same quantization strength, eliminating the subjective quality benefit of the chroma quantization technique.
After a First Examination Report in January 2020 and a hearing in April 2021, the Assistant Controller of Patents and Designs refused the application on 21 June 2022 under Section 15 of the Patents Act for lack of inventive step. The three prior art documents cited were: HEVC Screen Content Coding Draft Text 1 (‘D1’), a paper on in-loop colour-space transform (‘D2’), and PCT publication WO2015143671 (‘D3’). NEC appealed under Section 117A(2) of the Patents Act.
Issues Before the Court
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- Whether the application satisfied inventive step under Section 2(1)(ja) in light of D1, D2, and D3, specifically the feature of deriving an adaptive chroma quantization offset for each of a plurality of colour spaces
- Whether D3, published after the priority date, was validly cited as prior art under Section 13(1)(b), given that its claims had not been granted
NEC’s Arguments
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- D1’s Section 8.6.2 discloses a chroma quantization offset for a plurality of colour components, not colour spaces; the concept of per-colour-space offset derivation is absent from D1
- D3 was published after the priority date and its claims had not been granted; it cannot constitute valid prior art for prior claiming under Section 13(1)(b)
- Corresponding patents were granted in the USA, Australia, and Japan, supporting the existence of inventive step
Controller’s Arguments
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- D1’s Sections 8.6.2, 8.4, and 8.6.8 read together disclose selecting from among colour spaces at coding unit level and deriving offset values for each; an offset of -5 or -3 when adaptive colour transform is applied, 0 when not
- D2 teaches delta QPs of (-5, -3, -5) for YCoCg; the reversal to 0 for the original colour space is implicit and obvious to a person skilled in the art
- NEC took contradictory positions: in post-hearing submissions it accepted D1 teaches per-colour-component offset derivation, then resiled from this in the appeal
Court’s Observations and Analysis
D1: Colour Space Switching and Adaptive QP Already Disclosed
The court found that D1, when Sections 8.6.2, 8.4, and 8.6.8 are read together, discloses selecting among a plurality of colour spaces at the coding unit level. Section 8.6.2 sets out equations through which the quantization parameter for each colour component is derived by applying an offset of -5, -3, or 0 depending on the adaptive colour transform flag: a flag value of 1 indicates the transform has been applied to the current coding unit. The combination of these sections discloses per-colour-space QP adjustment with different offset values depending on which colour space is active. The court held this directly anticipates the adaptive chroma quantization offset derivation feature that NEC claimed as its inventive contribution.
D2 and the Admissibility of D3
D2 explicitly discloses delta QPs of (-5, -3, -5) for YCoCg when colour space transform is applied. The court reasoned that a person skilled in the art would immediately understand that if the transform is not applied, the normal quantization parameter remains unmodified, implying a delta QP of 0 for the original colour space. This implicit understanding reinforces the prior art picture on per-colour-space adaptive offset derivation without requiring any creative step.
On D3, the court acknowledged NEC’s objection that it was published after the priority date and its claims had not been granted. However, the court held that D3’s claims must be read in conjunction with its specification, and that paragraph [0149] of D3 discloses two separate QP syntax elements for the first and second colour space respectively, indicating that QP adjustment is applicable to both colour spaces. The court did not rely solely on D3, but treated it as corroborative support alongside D1 and D2.
Contradictory Positions and the Inventive Step Conclusion
The court found NEC’s shifting positions damaging to its case. In post-hearing submissions before the Controller, NEC had accepted that D1 teaches derivation of an adaptive chroma quantization offset for each of the plurality of colour components. In the appeal, NEC argued that Section 8.6.2 describes no chroma quantization offset at all, and also argued that the section describes only an adjustment to the luma component. Neither of these positions was taken at the hearing stage. The court declined to accept arguments that contradicted concessions already made below, and held that in view of D1 and D2, the claimed subject matter was rendered obvious to a person skilled in the art. The appeal was dismissed.
Findings
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- D1, read across Sections 8.6.2, 8.4, and 8.6.8, discloses per-colour-space adaptive chroma quantization offset derivation, anticipating the key claimed feature
- D2 reinforces the prior art picture; D3 is admissible as a citation to the extent its claims are read with its specification
- The invention lacks inventive step under Section 2(1)(ja) of the Patents Act; NEC’s shifting positions between the examination stage and the appeal undermined its case
- The Controller’s order dated 21 June 2022 refusing the application under Section 15 is upheld; the appeal is dismissed
Case Citation: NEC Corporation v. Assistant Controller of Patents and Designs, C.A.(COMM.IPD-PAT) 486/2022, Delhi High Court, decided on 28 March 2026. Available at http://indiankanoon.org/doc/79381597/
Authored by Gaurav Mishra, IP Attorney, BananaIP Counsels