HD-MAC

Abstract: The authors discuss the problem of MAC compatible broadcasting of a high definition television (HDTV) signal. The problem of MAC compatible broadcasting is studied as part of the Eureka 95 project and is called HD-MAC coding. The HD-MAC coding system is designed to achieve a bandwidth reduction factor of about 4. The authors describe several techniques that make this possible. The coding system presented is a synthesis of all the possible techniques that are under study. In practice the resulting system may not necessarily incorporate all these described techniques. An additional digital control signal of 1 Mb/sec. is transmitted in the vertical blanking interval. This signal is called the DATV signal where DATV stands for digitally assisted television.

Abstract: Device for decoding television signals previously coded on broadcasting with a view to transmission carried out, depending on the movement observed in the original images, at a first, at a second or at a third rate. This device comprises: (A) a storage sub-unit (710) comprising three frame memories (711, 712, 713), (B) a sub-unit (720) for reconstructing grid cells and for filtering, comprising a first, a second and a third decoding channel (722, 726; 723, 727; 724, 728), and (C) a movement-compensation sub-unit (730) provided in order, alternatively, to store temporarily a movement-compensation signal during the restoring of frames of specified parity or to participate, with the aid of the said movement-compensation signal, in the restoring of the frames of opposite parity. Application : high-definition television receivers.

Abstract: In a method of encoding a television signal having a video signal, the method comprising producing an encoded television signal in accordance with a motion-compensated processing of the video signal, determining vectors in a first picture period of two consecutive picture periods of the video signal, and, in a second picture period of the said two consecutive picture periods, determining pointers to the vectors determined in the first picture period, a substitute pointer pointing to a vector which is indeed to be transmitted is searched if a pointer thus determined does not point to a vector to be transmitted, so that a television signal encoding with an improved picture quality can be obtained.

Abstract: Television alignment process of the type consisting in aligning, successively at each line forming an image, a porch of a television signal S1(t) at the beginning of the current line, on the porch of the preceding line for restitution of the continuous component of the television signal S1(t). The process consists, during a given duration T2, in reducing the noise superimposed on the porch of the television signal S1(t), in estimating, during a given duration T1 included in the duration T2, the level of the porch of the current line based on the level of the porch of the preceding line, and in subtracting the estimation of the porch level from the television signal S1(t). Application to all current television standards, especially HD MAC and D2 MAC standards.