Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1996-07-18
2001-01-16
Le, Vu (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C348S385100, C348S388100
Reexamination Certificate
active
06175595
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of decoding a bitstream including a plurality of multiplexed digital video bitstreams corresponding to previously coded signals, said method comprising in cascade the steps of:
receiving n digital video bitstreams in the form of a single multiplexed bitstream originating from previous transmitting and/or storage means;
selecting one single digital video bitstream for display; and
decoding the selected digital video bitstream.
The invention also relates both to a device for decoding a bitstream including a plurality of multiplexed digital video bitstreams corresponding to previously coded signals, said device comprising:
means for receiving n digital video bitstreams in the form of a single multiplexed bitstream originating from previous transmitting and/or storage means and demultiplexing said multiplexed bitstream;
storing means;
means for selecting one single digital video bitstream for display; and
means for decoding the selected digital video bitstream, and to a reception equipment comprising such a decoding device.
This invention finds an application in the field of television (standard, high definition, or interactive television for instance), and particularly in the field of video terminals or receivers based on the MPEG standard.
The european patent application no. 0566092 describes an apparatus for decoding compression-coded moving picture signals, comprising, in one of the proposed embodiments, a single decoder provided for decoding an input bitstream composed of multiplexed coded signals corresponding to independent original sequences of images. This apparatus associates to said decoder control means allowing to reconstruct and display from the output signals of the decoder the pictures corresponding to one of the original video sequences. However, the method carried out in such an apparatus does not take into account the problems which appear in case of switching from a sequence to another one and, more particularly, the troublesome factors which considerably increase the waiting time for pictures from the new video sequence.
SUMMARY OF THE INVENTION
It is therefore a first object of the invention to propose a method of decoding a bitstream including a plurality of multiplexed digital video bitstreams which allows to switch fast from one of the coded bitstreams to another one.
To this end, the invention relates to a method as defined in the preamble of the description, in which said coded digital signals correspond at least to frames, said intra, which are coded without any reference to any other previous frames, the selected digital video bitstream being presented for decoding and display and coded signals corresponding to an intra frame of at least one of the (n-
1
) other bitstreams being stored for immediate access by the viewer.
In a particular application of the method, said coded digital signals correspond to frames, said intra, which are coded without any reference to any other frame or to frames said predicted or interpolated according to the fact that, in agreement with the MPEG standard, they are respectively predicted by motion-compensated prediction from an earlier intra or predicted frame or bidirectionally interpolated from an earlier and a later frame, the selected digital video bitstream being presented for decoding and display, and at least the coded signals corresponding to an intra frame of at least one of the (n-
1
) other bitstreams being stored for immediate access by the viewer.
By implementing this decoding method, especially in the case of coded signals being in agreement with the MPEG standard, switching is thus considerably faster than when a conventional decoder is used. Preferably said stored coded signals are the most recently received intra frame, rather than storing the whole bitstream representing a given period of time. A picture is then displayed nearly instantaneously upon switching to an other video sequence.
In more sophisticated implementations, said stored coded signals belong to the two bitstreams corresponding to the most immediate access by the viewer, or, more generally, to the (n-
1
) other bitstreams.
It is another object of the invention to propose a device for decoding multiplexed digital video bitstreams which allows to implement said decoding method.
To this end, the invention relates to a device as defined in the preamble of the description and in which said coded digital signals correspond at least to frames, said intra, which are coded without any reference to any other previous frame, and said storing means comprise, while the selected digital video bitstream is presented for decoding and display, a buffer for storing coded signals that correspond to an intra frame of at least one of the (n-
1
) other bitstreams, for immediate access by the viewer.
Notwithstanding the increase of the size of the physical memory, the access delay in case of switching on from one input bitstream to another is considerably reduced, which is considered as very advantageous by the consumers. Only a residual waiting time is to be observed before the concerned sequence begins to exhibit motion.
Obviously the invention also relates, in a particular embodiment, to a decoding device in which said coded digital signals correspond to frames, said intra, which are coded without any reference to any other frame or to frames said predicted or interpolated according to the fact that, in agreement with the MPEG standard, they are respectively predicted by motion-compensated prediction from an earlier intra or predicted frame or bidirectionally interpolated from an earlier and a later frame, and said storing means comprise, while the selected digital video bitstream is presented for decoding and display, a buffer for storing at least the coded signals corresponding to an intra frame of at least one of the (n-
1
) other bitstreams, for immediate access by the viewer.
In other embodiments, said storing means may comprise two parallel buffers for storing at least the coded signals corresponding to an intra frame of the two bitstreams corresponding to the most immediate access by the viewer, or more generally (n-
1
) parallel buffers for storing at least the coded signals corresponding to an intra frame of each of the (n-
1
) other bitstreams.
Preferably said buffer(s) is (are) provided for storing within each of said bitstream(s) the most recently received intra frame. Moreover, the buffers may together constitute a single physical memory.
It is still another object of the invention to propose a reception equipment including such a decoding device.
To this end, the invention relates to a reception equipment comprising a decoding device such as indicated above and provided in the form of a sub-assembly which comprises the following circuits:
a demultiplexer, provided for separating the input multiplexed bitstream into n respective demultiplexed digital video bitstreams corresponding to original sequences, of images;
parallel buffers;
a selector provided for enabling said viewer to select for decoding and display one of said bitstreams stored in one buffer, only a limited part of the other non-selected demultiplexed bitstreams being stored within the (n-
1
) other buffers, and said limited part being at least the coded signals corresponding to a previous intra frame of each bitstream;
a decoder of said selected bitstream;
display means, in the form of a screen of a television set.
Preferably, said sub-assembly and said television set constitute one single apparatus.
REFERENCES:
patent: 5029014 (1991-07-01), Lindstrom
patent: 5343250 (1994-08-01), Iwamura
patent: 5361098 (1994-11-01), Lucas
patent: 5502493 (1996-03-01), Meyer
patent: 5592398 (1997-01-01), Terauchi et al.
patent: 5594492 (1997-01-01), O'Callaghan et al.
patent: 5719641 (1998-02-01), Mizoguchi
patent: 5724091 (1998-03-01), Freeman et al.
patent: 5790177 (1998-08-01), Kassatly
patent: 5815502 (1998-09-01), Saito et al.
patent: 5861881 (1999-01-01), Freeman et al.
patent: 5949476 (1999-09-01), Pocock et al.
pate
Gathman Laurie E.
Le Vu
U.S. Philips Corporation
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