WO2002089475A2

WO2002089475A2 - System for recording and reading audiovisual information

Info

Publication number: WO2002089475A2
Application number: PCT/IB2002/001488
Authority: WO
Inventors: Declan P. Kelly; Nicolas De Jong
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2001-05-01
Filing date: 2002-04-24
Publication date: 2002-11-07
Also published as: KR20040000313A; CN1465179A; WO2002089475A3

Abstract

A system (100) comprising a first apparatus (101), which is adapted to store and/or read audiovisual information into or from a memory (112), and a second apparatus (102), which is adapted to control the first apparatus (101). The second apparatus (102) comprises a receiver (132) for receiving audiovisual information from the first apparatus (101), and a display device (124) for displaying the received audiovisual information. To transmit the audiovisual information from the first apparatus (101) to the second apparatus (102) in an efficient way, the audiovisual information is first compressed by a compression unit (115). The invention also relates to methods of compressing the audiovisual information.

Description

System for recording and reading audiovisual information

The invention relates to a system comprising a first apparatus which is adapted to store and/or read a stream of audiovisual information into or from a memory, and a second apparatus which is adapted to control the first apparatus, the second apparatus comprising a display device. The invention also relates to a method of transmitting and receiving a stream of audiovisual information.

Such a system is known from US 5,537,107.

A system of this type provides the possibility of displaying audiovisual information on a remote control unit of a video recorder or a video camera so as to enhance the interaction of a user with the system operated by means of the remote control unit.

A problem in such a system is that audiovisual information, as is generally stored in the memory of, for example, a video recorder, is too broadbanded to be sent wirelessly to the remote control unit.

It is an object of the invention to meet this problem of a too large bandwidth of a standard audiovisual signal.

According to the invention, this object is achieved in a system which is characterized in that the first apparatus comprises a compression unit for compressing the stream of audiovisual information before it is transmitted, and the second apparatus comprises a decompression unit for decompressing the stream of audiovisual information transmitted by the first apparatus, after this stream has been received. By compressing the stream of audiovisual information before transmitting it, less bandwidth is required for transmitting the audiovisual information from the first apparatus to the second apparatus. An embodiment of the system according to the invention is characterized in that the compression unit is adapted to periodically select an image from the stream of audiovisual information. By transmitting images from the stream of audiovisual information from the video recorder to the remote control unit at a certain period, a stream is produced which comprises fewer images than the original stream of audiovisual information. Consequently, less information needs to be transmitted from the first apparatus to the second apparatus.

A further embodiment of the system according to the invention is characterized in that the compression unit is adapted to further compress the selected image. When the images themselves are compressed and are transmitted as separate images from the first apparatus to the second apparatus, the complexity of the second apparatus may be decreased. This is possible because the decompression of images is less complex than the decompression of a compressed stream of audiovisual information. An additional advantage is that the complexity of the second apparatus will not become too high, with the further advantage that the second apparatus is easier to handle than a more complex apparatus. This, in turn, has the further advantage that it contributes to the convenience of use of the system.

The method according to the invention is characterized in that the first apparatus compresses the stream of audiovisual information and the second apparatus decompresses the encoded stream of audiovisual information. These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

In the drawings: Fig. 1 shows an embodiment of the system according to the invention,

Fig. 2 shows an image to illustrate a first method of compressing visual information,

Fig. 3 shows an image to illustrate a second method of compressing visual information.

Fig. 1 shows a system 100 which is a possible embodiment of the invention. The system 100 comprises a video recorder 101 and a remote control unit 102. In the embodiment shown, the video recorder 101 is a digital video recorder, but it may be alternatively an analog video recorder in another embodiment. Moreover, the apparatus 101 may be alternatively a video camera. A user may operate the video recorder by way of entry means 121 on the remote control unit 102. The entry means 121 may comprise a matrix of keys, but it may be alternatively a touch screen. The remote control unit 102 further comprises a first transmitter 122 for transmitting the command, given by way of the entry means 121, via a first signal 131 to the video recorder 101. Within the video recorder 101, the command is received by a first receiver 114.

The first receiver 114 transmits the command to a central processing unit 111 which executes the user's command. In a video recorder, such as the video recorder 101, the commands will mostly relate to the playback of audiovisual information from a memory. To perform these commands, the processing unit 111 is connected to a memory 112. The processing unit 111 is further connected to a first connection 116 to which a display device such as a television receiver can be connected. If the user gives the command for displaying audiovisual information stored in the memory 112 on a display device connected to the first connection 116, processing unit 111 searches the desired audiovisual information in the memory 112 and sends this information to the first connection 116.

To enhance interaction of the system 100 with the user and to improve the convenience of use, the remote control unit 102 comprises a display device 124 for displaying audiovisual information. In the shown embodiment of the invention, the display device 124 is an LCD screen so as to limit the size and weight of the remote control unit 102. The user may display audiovisual information on the display device 124 which is different from the audiovisual information displayed on a further display device connected to the connection 116. This is possible when the processing unit 111 is capable of reading a plurality of streams of audiovisual information from the memory 112. This is the case in the illustrated embodiment of the invention.

It is a great advantage that audiovisual information other than the audiovisual information displayed on a further display device can be displayed on the display device 124 when the user wants to search audiovisual information from the memory 112 by using trick play modes such as fast forward and fast rewind which are known to those skilled in the art, while possible further users may watch, for example, a movie on the further display device connected to connection 116.

To display the audiovisual information on the display device 124, the audiovisual information is to be transported from the video recorder 101 to the remote control unit 102. In the illustrated embodiment of the invention, the video recorder 101 is a digital video recorder, and the audiovisual information stored in the memory 112 has an MPEG2 format. However, this may be a different format, or the audiovisual information from the memory 112 may not be compressed at all, which does not detract from the scope of the invention. As stated hereinbefore, the connection between the video recorder 101 and the remote control unit 102 is wireless, and the communication between the video recorder 101 and the remote control unit 102 is realized, for example, via the first signal 132. This is an infrared signal in the illustrated embodiment of the invention.

A bitrate of at least 4 Mb/s is required for a PAL quality of a stream of audiovisual information in MPEG2 format. A maximum bitrate of 4 Mb/s through an infrared connection is possible with a synchronized connection and the IrDA protocol, but the distance between the transmitter and the receiver should not be larger than 30 cm. In this case, it has been assumed that the remote control unit is considered to be a low-power device. The reason is that a large battery makes the remote control unit less easy to handle, which is at the expense of its convenience of use. Said restriction as regards the distance is undesirable in the embodiment according to the invention, because this will be at the expense of convenience of use.

If a reasonable lifetime of the battery of the remote control is to be guaranteed, it will therefore be undesirable to transmit a stream of audiovisual information of PAL quality in MPEG2 format from the video recorder 101 to the remote control unit 102. Since audiovisual information in the illustrated embodiment of the invention is stored in this format in the memory 112 of the video recorder 101, this information is to be further compressed before it is sent to the remote control unit 102 by means of an infrared signal 132.

In the embodiment shown, the video recorder 101 comprises a compression unit 115 for compressing the audiovisual information. The audiovisual information may be compressed by reducing the resolution of the visual part of the audiovisual information. In Fig. 2, a first image 201 shows the original visual information and a second image 202 shows the compressed visual information, in which the visual part of the audiovisual information has been compressed by reducing the resolution.

Compression is alternatively possible by periodically selecting a frame of the visual part of the audiovisual information and by sending this frame as an image from the video recorder 101 (Fig. 1) to the remote control unit 102 (Fig. 2). This is illustrated in Fig. 3. In this Figure, a first series 301 shows the uncompressed stream of audiovisual information, and a second series 302 shows the compressed stream of audiovisual information. The compression method shown in Fig. 3 selects every second frame of a stream of audiovisual information so that the quantity of data is halved. For example, of the first series 301 comprising five frames, a first frame 311 is selected for the second series 302, as well as a third frame 313 and a fifth frame 315. A second frame 312 and a fourth frame 314 are not selected. In this way, the second series 302, which is a compressed version of the first series 301, comprises a sixth frame 321, which corresponds to the first frame 311 of the first series 301, a second frame 322, which corresponds to the third frame 313 of the first series 301, and a third frame 323 which corresponds to the fifth frame of the first series 302.

It is possible to subsequently also compress the selected images themselves, for example, in accordance with the JPEG standard, which is known to those skilled in the art, before the compressed audiovisual information is sent from the video recorder 101 (Fig. 1) to the remote control unit 102 (Fig. 1). Sending separate images has the advantage that less hardware is required for decompressing images compressed in accordance with the JPEG standard, as compared with decompression of audiovisual information compressed in accordance with the MPEG2 standard. The compressed audiovisual information is sent to the remote control unit 102 (Fig. 1) where it must be decompressed again. For convenience of use, it is preferable to use a simple remote control unit. It is thus advantageous to send the visual part of the audiovisual information in separate images from the video recorder 101 (Fig. 1) to the remote control unit 102 (Fig. 1).

As already stated hereinbefore, the audiovisual information is stored in an MPEG2 format of PAL quality in the memory 112 in the illustrated embodiment of the invention. A further method of compressing the information is to compress the audiovisual information in accordance with a different compression standard at which higher compression factors are possible, such as MPEG4. If this method is combined with other illustrated methods of compressing the visual part of the audiovisual information, large compression ratios can be achieved.

The sound information may also be compressed, for example, in accordance with the MP3 standard, which is known to those skilled in the art.

Fig. 1 further shows that the video recorder 101 comprises a second transmitter 113 which transmits the audiovisual information compressed by compression unit 115 to the remote control unit 102. In the illustrated embodiment of the invention, the audiovisual information is transmitted by means of the infrared signal 132, but it will be evident to those skilled in the art, that this may be alternatively, for example, a radio signal in accordance with the Bluetooth protocol.

The remote control unit 102 further comprises a second receiver 123 which can receive the signal 132 with the audiovisual information transmitted by the second transmitter 113. From the second receiver, the compressed audiovisual information is passed on to a decompression unit 125 in which the compressed audiovisual information is decompressed. The compression unit is connected to the display device 124 on the remote control unit so as to display the visual part of the decompressed audiovisual information. In the illustrated embodiment of the invention, the decompression unit 125 is also connected to a second connection 126 to which a headphone may be connected. In this way, the sound part of the audiovisual information may also be passed on to the user without any hindrance to possible further users. However, it is of course alternatively possible to provide the remote control unit 102 with a loudspeaker.

In summary, the invention relates to a system 100 (Fig. 1) comprising a first apparatus 101 (Fig. 1), which is adapted to store and/or read audiovisual information into or from a memory 112 (Fig. 1), and a second apparatus 102 (Fig. 1), which is adapted to control the first apparatus 101 (Fig. 1). The second apparatus 102 (Fig. 1) comprises a receiver 132 (Fig. 1) for receiving audiovisual information from the first apparatus 101 (Fig. 1), and a display device 124 (Fig. 1) for displaying the received audiovisual information. To transmit the audiovisual information from the first apparatus 101 (Fig. 1) to the second apparatus 102 (Fig. 1) in an efficient way, the audiovisual information is first compressed by a compression unit 115 (Fig. 1). The invention also relates to methods of compressing the audiovisual information.

Claims

CLAIMS:

1. A system (100) comprising a first apparatus (101), which is adapted to store and/or to read a stream of audiovisual information into or from a memory (112), the first apparatus comprising a transmitter (113), which is adapted to transmit the stream of audiovisual information, and a second apparatus (102), which is adapted to control the first apparatus (101), the second apparatus comprising a receiving device (123), which is adapted to receive the stream of audiovisual information transmitted by the first apparatus, a display device (124), which is adapted to display at least a part of the received stream of audiovisual information, characterized in that the first apparatus (101) comprises a compression unit (115) for compressing the stream of audiovisual information before it is transmitted, and the second apparatus comprises a decompression unit (125) for decompressing the stream of audiovisual information transmitted by the first apparatus (101), after said stream has been received.

2. A system as claimed in claim 1, characterized in that the compression unit (115) is adapted to reduce the resolution of the visual part of the stream of audiovisual information.

3. A system as claimed in claim 1, characterized in that the compression unit (115) is adapted to periodically select an image from the stream of audiovisual information.

4. A system as claimed in claim 3, characterized in that the compression unit

(115) is adapted to further compress the selected image.

5. A system as claimed in claim 1 , characterized in that the compression unit

(115) is adapted to further compress a stream of audiovisual information which has already been compressed.

6. A system as claimed in claim 1, characterized in that the second apparatus

(102) has an output for sound information (126).

7. A method of transmitting and receiving a stream of audiovisual information by using a system comprising a first apparatus (101), which is adapted to transmit a stream of audiovisual information, and a second apparatus (102), which is adapted to receive the stream of audiovisual information, characterized in that the first apparatus (101) compresses the stream of audiovisual information, and the second apparatus (102) decompresses the encoded stream of audiovisual information.

8. A method as claimed in claim 7, characterized in that compression comprises the step of reducing the resolution of the stream of audiovisual information.

9. A method as claimed in claim 7, characterized in that compression comprises the periodical selection of an image from the stream of audiovisual information.

10. A method as claimed in claim 9, characterized in that compression comprises the step of compressing the selected image.

11. A method as claimed in claim 7, characterized in that compression comprises the step of further compressing a stream of audiovisual information which has already been compressed.