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Subject: search.filters.subject.H.264/AVC

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    Increase of embedding capacity of the H.264/AVC data hiding based on the intra-prediction modes
    (CERIST, 2011-09) Bouchama, Samira; Hamami, Latifa; Aliane, Hassina
    Data hiding methods applied to the newest video codec H.264/AVC are exploiting several modules of this codec such as the discrete cosine transform (DCT) coefficients and the intra prediction modes. The objective is to realize a good compromise between the embedding capacity, the increase in bitrate and the video quality, to satisfy several applications such as authentication or covert communication. In this paper we present a new approach to exploit the intra prediction modes for data hiding of the 4x4 luminance blocks. The objective is to ensure a good data embedding capacity and to preserve the encoding and the decoding times to satisfy reel time applications. The proposed method is based on dividing the intra prediction modes into four groups. Each group in composed of modes that have close prediction directions. Embedding the secret data is based on applying modification between modes of the same group in order to maintain visual quality and limit the number of additional calculation procedures. The increase of embedding capacity relies on the group composed on four modes since it allows the embedding of two bits per mode instead of one.
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    A comparative study between compressed video watermarking methods based on DCT coefficients and intra prediction
    (CERIST, 2011-09) Bouchama, Samira; Hamami, Latifa; Aliane, Hassina
    Several watermarking methods have been applied to the newest video codec H.264/AVC to satisfy different applications such as authentication, tamper proof and copyright protection. Our objective through this paper is to present a comparative study between watermarking methods based on the quantized (Q) DCT coefficients and those based on the intra prediction of the 4x4 luma blocks, in terms of embedding capacity, video quality and bitrate. The use of intra prediction modes is motivating because it is possible to embed a relatively high embedding capacity while preserving the video quality; however it seems difficult to maintain the bitrate. In this paper we show that the Intra prediction based method outperforms the QDCT based method using the same codec configuration.
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    H.264/AVC Data Hiding Algorithm with a Limitation of the Drift Distortion
    (CERIST, 2012) Bouchama, Samira; Hamami, Latifa; Aliane, Hassina
    Many data hiding algorithms have been proposed for the latest video codec H.264/AVC, most of them are based on the 4x4 luma DCT coefficients. However, the drift distortion is the main reason which limits the embedding capacity in data hiding algorithms based on DCT coefficients. Few methods have been proposed to compensate or eliminate the error propagation. Though, they are either non-blind, only detectable or need prior knowledge of the encoded blocks and thus cannot be used for real time broadcasting. In this paper we show that it is possible to reduce considerably the error propagation for real time applications. The proposed algorithm exploits the method of watermarking paired-coefficients in each block in order to bring the error to the middle of the block matrix. We evaluate the distortion caused by each paired-coefficients in order to give a watermarking priority to the pairs which introduce the minimum error. The proposed scheme offers a very good compromise between the video distortion, the increase in bitrate and the embedding capacity.
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    H.264/AVC data hiding based on Intra prediction modes for real time applications
    (CERIST, 2012) Bouchama, Samira; Hamami, Latifa; Aliane, Hassina
    A compromise is usually made between the different constraints of video data hiding methods, which seems more difficult to achieve for real time applications. In this paper, a new data hiding approach is presented for the video codec H.264/AVC. This method uses the intra prediction modes for the 4x4 luminance blocks. The objective is to ensure a high data embedding capacity and to preserve the encoding and the decoding times in order to satisfy real-time applications. The data embedding is based on changing a mode to the one of the closest direction. Good results have been obtained in terms of increasing the embedding capacity, maintaining the visual quality and limiting the additional processing time.
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    Error Drift Compensation for Data Hiding of the H.264/AVC
    (CERIST, 2013) Bouchama, Samira; Hamami, Latifa; Aliane, Hassina
    The error propagation problem is one of the most attractive issues in the field of data hiding of compressed video because the achievement of several data hiding characteristics remains dependant on it. In this paper, a solution to compensate the error propagation is proposed for data hiding of the H.264/AVC. The error compensation is performed by a prior measurement of the introduced error in the watermarked block or in the neighbouring blocks. Two schemes are proposed: The first algorithm exploits the method of watermarking paired-coefficients in each block in order to bring the error to the middle of the block matrix. The distortion caused by each paired-coefficient is calculated in order to give a watermarking priority to the pairs which introduce the minimum error. In the second scheme, the error estimated in the neighbouring blocks is reduced from the residuals during the encoding process. In both schemes, results show that an important improvement of the video quality can be achieved and a good compromise is provided between the video distortion, the bitrate and the embedding.