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Cinavia, originally called Verance Copy Management System for Audiovisual Content (VCMS/AV),〔(【引用サイトリンク】title=Verance Milestones )〕 is an analog watermarking and steganography system under development by Verance since 1999, and released in 2010. In conjunction with the existing Advanced Access Content System (AACS) digital rights management (DRM) inclusion of Cinavia watermarking detection support became mandatory for all consumer Blu-ray Disc players from 2012. == Design == The watermarking and steganography facility provided by Cinavia is designed to stay within the audio signal and to survive all common forms of audio transfer, including lossy data compression using discrete cosine transform, MP3, DTS, or Ogg Vorbis. It is designed to survive digital and analogue sound recording and reproduction via microphones, direct audio connections and broadcasting, and does so by using audio frequencies within the hearing range. It is monaural and not a multichannel codec. Cinavia's in-band signaling introduces intentional spread spectrum phase distortion in the frequency domain of each individual audio channel separately, giving a per-channel digital signal that can yield up to around 0.2 bits per second〔Note: Cinavia's experimental patents make reference to up to 20 kilobits per second, but with high psychoacoustic visibility. The Cinavia standard as implemented in the Blu-ray Disc standards uses 3 bits per 15 seconds.〕—depending on the quantization level available, and the desired trade-off between the required robustness and acceptable levels of psychoacoustic visibility. It is intended to survive analogue distortions such as the wow and flutter and amplitude modulation from magnetic tape sound recording. On playback, no additional audio filters are used to cover up the distortions and discontinuities introduced. The signal survives temporal masking and sub-band coding by operating on the fundamental frequency and its subharmonic overtones, and by dealigning the phase relationship between the strongest signal and its subharmonics. Each phase discontinuity introduced by the encoder will result in a corresponding pulse of wideband white noise, so a further range of additional distortions are introduced as a noise mitigation strategy to compensate. The desired hidden digital data signal is combined in the distortion step using a pre-determined pseudorandom binary sequence for audio frame synchronization and large amounts of forward error correction for the hidden data to be embedded. The watermark is only embedded when certain signal-to-noise ratio thresholds are met and is not available as a continuous signal—the signal must be monitored for a period of time before the embedded data can be detected and recovered. Extraction of the hidden signal is not exact but is based on recovering the convolutional codes through statistical cross-correlation. The Blu-ray Disc implementation of Cinavia is designed to cover two use-cases: the first is the provision of a Cinavia watermark on all movie theater soundtracks released via film distribution networks; the second use-case is for the provision of a Cinavia watermark on all Blu-ray Disc releases that points to the presence of an accompanying AACS key. If a "theatrical release" watermark is detected in a consumer Blu-ray Disc audio track, the accompanying video is deemed to have been sourced from a "cam" recording. If the "AACS watermark" is present in the audio tracks, but no accompanying and matching AACS key is found on the disc, then it is deemed to have been a "rip" made by copying to a second blank Blu-ray Disc. known hardware players which can detect Cinavia watermarks include the PlayStation 3 (began with v3.10 System Software), as well as newer Blu-ray Disc players. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cinavia」の詳細全文を読む スポンサード リンク
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