This invention relates to a device for receiving and displaying television images comprising buffer means for storing television images. The invention also relates to a television apparatus provided with such a device.
A device of the type described in the opening paragraph is known from EP-B-0 375 764. The known device is intended for rapidly skipping commercials. If a user wants to watch a television program in such a way that he can skip the commercials in the television program, a number of minutes of the television program corresponding approximately to the expected total period of time of the commercials must first be stored in the buffer means. Subsequently, the device can be switched to a combined recording and display state at which the television images are read at the xe2x80x9cnormalxe2x80x9d rate so that the user can only then watch the television program. When the user watches a commercial during display, he can switch the device to a state at which the television images are read from the buffer means in an accelerated way. At the end of the commercials, the user can again switch the device to the previously mentioned combined recording and display state. By watching the commercials in an accelerated way, the period of time of an interruption in a program comprising commercials will be reduced.
It is an object of the invention to provide a device having a more user-friendly facility of rapidly skipping the commercials in a television program.
To this end, the device according to the invention is characterized in that the buffer means are adapted to receive television images at a first frame frequency and to supply television images at a second frame frequency, a quantity X being defined as being X equal to the number of consecutive television images, stored in the buffer means, between an image read from the buffer means at a given instant and an image written at substantially the same instant, in that X increases with time in the first state and decreases with time in the second state, and in that the device comprises control means for generating a first control signal for bringing the device from the first to the second state, and a second control signal for bringing the device from the second to the first state.
The invention provides a device in which it is no longer necessary to store a number of minutes of the television program corresponding to the period of time of the commercials to be expected in the television program into the buffer means and subsequently start watching the television program. The invention provides the possibility of watching these commercials simultaneously with the reception of the beginning of the television program. To be able to skip the expected commercials rapidly, a slightly larger number of television images are stored in the buffer means per unit of time in a first state as compared with the number of television images read, so that at the instant when a block of commercials in a program is displayed and watched by the user, this block is approximately entirely stored in the buffer means. The user can now switch the device to a second state so that the block of commercials is skipped in an accelerated way. In order that the user can continue watching the program, he will then switch the device to the first state again.
The device according to the invention has the extra advantage that the buffer means may be smaller because it need only be approximately the size of one inserted block of commercials.
A first embodiment of the device according to the invention is characterized in that the buffer means are adapted to store television images received at the input of the buffer means at the first frame frequency and to read television images stored in the buffer means at the second frame frequency and supply said images at the output, wherein the first frame frequency is larger than the second frame frequency, the buffer means, in the first state, being adapted as a FIFO and, in the second state, being adapted to supply each time N television images of successive groups of M consecutive television images stored in the buffer means at the output of said buffer means, N and M being positive integers and chosen to be such that X decreases with time. In this embodiment, the value of the first frame frequency at the input of the buffer means in the first state is equal to the value of the first frame frequency in the second state. The values of the second frame frequency at the output of the buffer means are equal to each other in the first and the second state. This has the advantage that the device does not need to be further adapted as far as possible pre-processing and post-processing means for switching from the first to the second state, or vice versa, are concerned. In the first state, all received television images are displayed at the output in the same order. In the second state, a part of the received television images is displayed at the output of the buffer means. Normally, the first frame frequency will be 25 Hz. This means that, in this embodiment, the display tube connected to the output must be capable of displaying television images at the lower, second frame frequency which is, for example 22 Hz.
A second embodiment of the device according to the invention is characterized in that the buffer means are of the FIFO type and are adapted to store television images received at the input of the buffer means at the first frame frequency, and to read television images stored in the buffer means at the second frame frequency and supply them at the output, the second frame frequency in the first state being smaller than the first frame frequency, and the second frame frequency in the second state being larger than the first frame frequency. In this embodiment, all received and stored television images are supplied at the output of the buffer means in the first and the second state. In this embodiment, the frame frequency at the output of the buffer means is, for example, 25 Hz in the first state and, for example, 100 Hz in the second state. In this embodiment, the image-processing means in the device subsequent to the buffer means should be capable of processing television images at both frame frequencies.
A third embodiment of the device according to the invention is characterized in that the buffer means are adapted to receive and supply television images at the first frame frequency at their input and output, respectively, said buffer means, in the first state, being adapted to supply each received television image at least once and a part of the received television images more than once at the output of said buffer means. In this embodiment, the frame frequencies at the input and output of the buffer means are equal and do not differ in the first and the second state. This has the advantage that the device in accordance with the third embodiment can be used in a standard television apparatus in which no costly adaptations are necessary. In the first state, all received television images are displayed at the output once or several times in the same sequence. The television images can be stored in, or read from the buffer means several times and supplied from the output. In the second state, a part of the received and stored television images is displayed at the output of the buffer means.
Further embodiments and advantages of the device according to the invention are described in the dependent claims.