Television – Basic receiver with additional function – Multimode
Reexamination Certificate
1999-01-12
2002-12-03
Kostak, Victor R. (Department: 2711)
Television
Basic receiver with additional function
Multimode
C348S555000, C348S725000
Reexamination Certificate
active
06490001
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for receiving a digital television broadcast such as a digital ground wave broadcast or a digital cable broadcast, to a receiving apparatus capable of receiving both digital television broadcasts and current analog broadcasts, and to a receiving apparatus for receiving both digital and analog broadcasts.
2. Description of the Related Art
Digital broadcasting systems have been brought into use as television (TV) broadcasting systems following analog TV broadcasting systems.
A receiver for use in a digital broadcasting system such as a digital ground wave type broadcasting system or a digital cable type broadcasting system has a front end section, a transport section, an MPEG decoding section, a display processing section, and a control section. The front end section selects one of a plurality of carriers of electromagnetic waves received by an antenna, cancels ghost signals by using a digital filter (performs channel equalization), corrects errors, and outputs a transport stream. The transport section separates transport packets of the desired channel designated by a user from a plurality of channels multiplexed in the transport stream from the front end section, and descrambles the separated packets. The MPEG decoding section decodes MPEG-compressed video and audio signals in the desired channel transmitted through the medium of the transport packets output from the transport section to obtain video and audio outputs. The display processing section converts the MPEG-decoded images into a display format in accordance with the NTSC (National Television System Committee) system or the like. The control section is formed of a microcomputer or the like for controlling each section.
In the case of receiving an analog TV broadcast, a broadcast image can be immediately displayed on the screen of a display when a tuner selects the corresponding one of a plurality of carriers. Accordingly, in such receiving, the delay time between the moment at which a user inputs a command to change a channel and the moment at which an image and sound in a new channel are output depends only upon the time required for tuning in the tuner. In general, the time required for tuning in receivers for receiving analog TV broadcasts is about 200 to 300 msec. In analog TV broadcast receivers, no image is displayed for the time period corresponding to the delay time because only a distorted image can be displayed in the period corresponding to the delay time.
In the case of a receiving a digital TV broadcast, it is possible that about one second will be taken as a delay time between the moment at which a command to perform tuning for changing a channel is given and the moment at which an image appears on the screen of a display.
That is, for example, the time required for processing in the front end section, depending upon the number of taps of the digital filter for cancellation of ghost signals, is about 500 msec at the worst. A time of 100 msec is also required for MPEG decoding. Further, 30 msec is required for conversion of the MPEG-decoded output to a display format such as that in accordance with the NTSC system. The total delay time is the sum of these time periods and the tuner section processing time of about 200 to 300 msec.
To avoid display of a distorted image on the screen in the digital TV broadcast receiver, the method of displaying no image during the delay time may be used, as is in the conventional analog TV broadcast receiver. However, ordinary users, accustomed to the tuning speed of the existing analog TV broadcast receivers, are liable to feel that the above-mentioned delay in digital TV broadcast receivers is excessively long, and may be irritated when feeling a delay of display of a received image.
Moreover, many users expect the digital system to be higher in speed and quality than the analog system. For this reason, the above-described problem of a delay of receiving a digital TV broadcast is serious.
It is thought that analog broadcasting and digital TV broadcasting will coexist for a period of time, and that receivers capable of receiving both analog and digital TV broadcasts will be provided.
If so, and if it is impossible to immediately identify a channel designated by a channel selecting operation as an analog TV broadcasting channel or a digital TV broadcasting channel, a process is required in which tuning to the channel and reception of the channel are performed by each of analog and digital receiving sections to identify the channel. In such a case, however, the delay time before outputting an image and sound is further increased.
SUMMARY OF THE INVENTION
In view of the above-described circumstances, an object of the present invention is to provide a receiving apparatus and a receiving method arranged to reduce the delay time of tuning to and reception of a digital TV broadcast effectively and apparently.
To achieve the above-described object, according to a first aspect of the present invention, there is provided a television broadcast receiving apparatus comprising a tuner section for selecting one carrier from an input signal, a front end section for demodulating the carrier selected by the tuner section, the front end section having a channel equalizer formed of a digital filter, a transport section for separating a desired channel from a stream from the front end section, and for descrambling in the separated channel, a decoding section for decoding a signal in the separated desired channel to obtain at least one of an output video signal and an output audio signal, a display section for displaying an image based on the output video signal from the decoding section, a coefficient memory for storing equalizer coefficients to be supplied to the digital filter forming the channel equalizer, and control means for generating equalizer coefficients to be supplied to the channel equalizer by using the equalizer coefficients in the coefficient memory.
In this receiving apparatus, computation of equalizer coefficients, with which a longest processing delay is caused in the total processing delay of the front end section, which is particularly long, can be performed by using equalizer coefficients stored in the coefficient memory to increase the processing speed. The time period between the moment at which a user inputs a channel change command and the moment at which an image is thereafter output is thereby reduced.
In the above-described receiving apparatus, control means may update the equalizer coefficients stored in the coefficient memory by using the equalizer coefficients newly generated.
The equalizer coefficients in the coefficient memory are thereby updated to values closer to ideal values, thereby further increasing the equalizer coefficient computation speed.
The receiving apparatus may also have means for supplying a predetermined wait-time video signal to the display section for a time period before an output video signal is obtained from the decoding section.
According to this arrangement, a wait-time image, e.g., an image containing letters “Tuning . . . ” or the like is displayed instead of blanking the display before the received image is displayed, thereby relieving user's irritation during the waiting time.
In the above-described receiving apparatus, an image for identification of the selected desired channel is displayed by the display section for a time period before the desired video output is obtained from the decoding section.
For example, a logotype or the like of a broadcasting selected by a user is displayed on the screen during the waiting time, thereby further relieving user's irritation.
The above-described receiving apparatus may further have storage means for storing program information previously provided in the same channel as the above-mentioned desired channel, and the program information previously provided in the desired channel and read output from the storage means is displayed by the display section for a time period before the de
Shintani Peter
Usui Hirofumi
Kostak Victor R.
Lerner David Littenberg Krumholz & Mentlik LLP
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