Apparatus and service for transmitting video data

An apparatus for transmitting video data over an integrated services digital network. The apparatus comprises a video/audio receiving unit, a transmitting unit for transmitting video data over a switched connection to the video/audio receiving unit, a receiving unit for receiving request signals from the video/audio receiving unit, an encoding unit for encoding the video data using at least two different encoding methods, and a control unit cooperatively engaged with the encoding unit, wherein the encoding methods are selectable in accordance with the request made by a subscriber to select the type of encoding method and the time of encoding.

TECHNICAL FIELD
 The invention relates to an apparatus for transmitting video data into an
 integrated services digital network (NET). It is also directed to an
 apparatus for transmitting request signals into an integrated services
 digital network (NET). It is still further directed to a service for
 transmitting video data via an integrated services digital network.
 BACKGROUND OF THE INVENTION
 From the not yet published patent application P 1 95 24 704.3, there is
 known a service for transmitting video data of a video movie via a
 integrated services digital network. In a video server, there are stored
 several video movies, which are first selected from video telephones via
 request signals and subsequently transmitted to the respective video
 telephones via a switched connection. The encoding of the video data of
 the video movies is prearranged. The service is restricted to downloading
 of video movies in the form of a sequence of video images.
 SUMMARY OF THE INVENTION
 Therefore, it is an object of the invention to transmit video data in a
 more flexible manner.
 This object is solved by an apparatus for transmitting video data into an
 integrated services digital network, said apparatus comprising a
 transmitting unit for transmitting the video data over a switched
 connection, a receiving unit for receiving request signals, an encoding
 unit for encoding the video data using at least two different encoding
 methods, and a control unit with which the encoding method is selectable
 in accordance with information in the received request signals.
 This object is also solved by an apparatus for transmitting request signals
 into an integrated services digital network, said apparatus comprising a
 transmitting unit for transmitting the request signals over a switched
 connection, a receiving unit for receiving video data, a decoding unit for
 decoding the received video data by at least two different decoding
 methods, and a control unit for detecting the method by which the received
 video data were encoded and for selecting the decoding method in the
 decoding unit.
 The above object is still further solved by a service for transmitting
 video data via an integrated services digital network, wherein the video
 data to be transmitted are requested by request signals, wherein the
 requested video data are transmitted over a switched connection and
 wherein the encoding method used for transmitting the requested video data
 is selected from at least two different encoding methods through request
 signals.
 It is a particular advantage of the invention that received and stored
 still images can be processed later, e.g. the images can be printed by
 facsimile equipment or transmitted to a video telephone.

BEST MODE FOR CARRYING OUT THE INVENTION
 The first embodiment will now be described with reference to FIG. 1.
 FIG. 1 shows a transmission system SYS according to the invention. The
 transmission system SYS comprises an apparatus for transmitting video
 data, the apparatus in the form of a server SER and connected via an
 integrated services digital network NET, also called ISDN, to an apparatus
 for transmitting request signals in the form of a video telephone TEL2.
 A switched connection is established from the video telephone TEL2 to the
 server SER by dialing the server SER. Through request signals transmitted
 from the video telephone TEL2 to the server SER over the switched
 connection, video data stored in the server and/or an associated encoding
 method are selected. The selected video data are transmitted in real time
 from the server SER to the video telephone TEL2 over the switched
 connection.
 The server SER comprises a transmitting unit SEN, a receiving unit EMP, an
 encoding unit K and a control unit CTRL. The transmitting unit SEN is used
 to transmit selected video data into the integrated services digital
 network NET over a switched connection. The transmitting unit SEN
 comprises a unit for 2-wire-4-wire conversion and an amplifier.
 The receiving unit EMP is used to receive request signals from the
 integrated services digital network NET. The receiving unit EMP comprises
 a real time 2-wire-4-wire conversion, an amplifier and an echo
 compensator.
 The encoding unit K comprises two encoders for each switched connection.
 The encoding unit K may comprise, for example, 100 encoders, of which two
 encoders K1, K2 are depicted in FIG. 2. The encoder K1 is used to encode
 video data from a sequence of video images. The sequence of video images
 is, for example, a live television transmission. In the encoder K1, video
 data are encoded according to an interframe method. The interframe method
 advantageously uses the correlation between sequential video images. The
 encoder K1 is controlled by the control unit CTRL and receives from a
 camera CAM with a microphone a live-recording of sequential video images,
 encodes these video images according to the interframe method and
 transmits those encoded images to the control unit CTRL. A respective
 encoder is known from, for example, DE 36 13 343 A1.
 The encoder K2 is used to encode video data of selected frames. In the
 encoder K2, video data are encoded according to an intraframe method. The
 intraframe method advantageously uses the correlation of video data within
 a video image. A respective encoder is known from, for example, DE 36 13
 343 A1. The attainable compression of the data rate is less for the
 intraframe method than for the interframe method. The encoder K2 is
 controlled by the control unit. The resolution which the encoder K2 uses
 for encoding, is selectable. The encoder K2 receives the same video data
 as the encoder K1. The encoder K2 is controlled by the control unit CTRL
 and encodes video data of individually selected video images and transmits
 those encoded data to the control unit CTRL. One of the selected video
 images is the initial video image of the sequence to be transmitted, which
 is also transmitted to the encoder K1, so that encoder K1 can start the
 interframe method.
 The control unit CTRL is used to control the encoding unit K and the
 transmitting unit SEN as well as to execute an access control for the
 received request signals and to select the encoding method depending on
 the received request signals. For this purpose, the control unit CTRL
 comprises a microprocessor or a digital signal processor and a memory. The
 server SER can be dialed up from several video telephones simultaneously.
 In order to transmit the requested and selected video data simultaneously
 over several switched connections, the control unit further comprises
 several switching elements and a time multiplexer.
 The server SER further comprises an audio unit AUD, a video recording unit
 REC, a CD-recording unit CD and a data processing unit AUF, each of which
 is connected to the control unit CTRL.
 The audio unit AUD is used to encode the audio signals associated with a
 sequence of video images and to convey those encoded signals to the
 control unit CTRL. The transmission of the audio signals is performed
 independently of the encoding method and synchronized to the sequence of
 the video images. For this purpose, there is, for example, employed a
 switched connection having two channels carrying information, with the
 first information channel used for transmitting video data and the second
 information channel used for transmitting audio signals.
 The video recording unit REC comprises a plurality of video recorders. Each
 video recorder is used to receive a video cassette with a selected video
 movie to be transmitted over a switched connection. Each video recorder is
 controlled by the control unit CTRL.
 The CD-recording unit CD comprises a plurality of CD-recorders for playing
 Compact Disc Read Only Memories, also called CD-ROM. Each CD-recorder is
 controlled by the control unit CTRL, with the selected CD-ROM transmitted
 over a switched connection. On the video cassettes and the CD-ROM's, there
 are stored, for example, TV transmissions from the previous day or video
 clips.
 The data processing unit AUF is connected to an antenna ANT and a
 transmission line, for example by an optical fiber cable or a coaxial
 cable, for receiving respective TV transmissions or video movies. The data
 processing unit AUF is controlled by the control unit CTRL and comprises
 amplifiers, an optical/electrical converter and an equalizing network, an
 encoding unit and an audio unit which correspond to the above described
 encoding unit K and the already described audio unit AUD, performing
 identical functions.
 In the following, the transmission of video data and request signals
 between server SER and video telephone TEL2 will be described with
 reference to an example.
 In a basic connection configuration, a subscriber with a video telephone
 TEL2 is provided with two information channels with 64 kbits/s per
 channel, which are called B-channels, and with a signalling channel with
 16 kbits/s, also called D-channel, for transmitting and receiving
 information. The subscriber dials the number of the server SER. The
 switched connection is established via the D-channel. A menu is
 transmitted to the video telephone via the control unit CTRL. The
 subscriber sends request signals in the form of selection numbers
 corresponding to the suggestions in the menu to the server SER over the
 established switched connection. The control unit CTRL processes the
 request signals. The subscriber selection corresponds to, for example, a
 TV program which is recorded live by the camera CAM at the time of the
 call. The control unit CTRL first selects the encoder K2 for encoding the
 initial video image from the selected sequence of video images. The
 encoded initial video image is transmitted via the control unit CTRL and
 over the switched connection over a B-channel. Next, the control unit CTRL
 selects the encoder K1 for encoding all subsequent images and transmitting
 these images to the video telephone TEL2 of the subscriber. If during the
 transmission of the sequence of video images, the subscriber becomes
 interested in a specific video image, then the subscriber can request said
 selected image by way of another selection number for transmission at a
 time selected by the subscriber. The selection number is transmitted over
 the switched connection to the server SER in form of request signals. The
 control unit CTRL processes the request signals and subsequently controls
 the encoder K2 in such a way that the selected video image is encoded with
 higher resolution. The encoded selected video image requires a higher
 transmission bandwidth. However, since only 64 kbits/s are available, the
 selected video image is divided in the control unit into partial images
 for sequential transmission to the video telephone TEL2. Consequently, the
 image reconstruction in the video telephone TEL2 is slower. The
 subscriber, however, receives a video image with a higher image quality.
 As a result, a current separate frame from a sequence of video images is
 encoded and transmitted as a still image.
 During the transmission of the selected video image, the audio signals are
 transmitted synchronously with the sequence of video images. In this way,
 the subscriber is able to follow the audio portion of the TV program while
 watching the still image. In the video telephone TEL2, the selected still
 image can now be stored in memory by using another selection number and
 can be printed by a facsimile equipment or photographed or, for example,
 used a press photo, the switched connection has been disconnected. By
 using again another selection number, the subscriber can return to the
 live TV program. The method therefor has been described above.
 A second embodiment will now be discussed with reference to FIG. 2. FIG. 2
 shows a transmission system SYS according to the invention. The
 transmission system SYS is an apparatus for transmitting video data, the
 apparatus formed as video telephone TEL1 and connected via an integrated
 services network NET, also called ISDN, to an apparatus formed as video
 telephone TEL2, for transmitting request signals. The video telephone TEL2
 corresponds to the video telephone of FIG. 1.
 For the sake of simplification, both video telephones TEL1, TEL2 are
 depicted without the usual components, such as echo compensator, keypad,
 receiver and display. From video telephone TEL2 and by using a request
 signal, a subscriber can select video data residing in video telephone
 TEL1 as well as associated encoding method. The selected video data are
 transmitted over a switched connection via the integrated services digital
 network NET to the video telephone TEL2.
 The video telephone TEL1 comprises a control unit implemented as a
 microprocessor .mu.P1, a transmitting unit SEN1, a receiving unit EMP1 and
 an encoding unit K.
 The transmitting unit SEN1 is used to transmit selected video data into the
 integrated services digital network NET over a switched connection.
 The receiving unit EMP1 is used to receive request signals from the
 integrated services digital network NET.
 The encoding unit K is used to encode by two different encoding methods
 video data which are to be transmitted. The two encoding methods are
 distinguished from each other in that video data can be encoded with
 different resolution. A sequence of video images is encoded with a lower
 resolution, requiring less bandwidth for transmission. Selected separate
 frames are encoded with a high resolution, requiring a large bandwidth for
 transmission. Switching between these two encoding methods is controlled
 by software through the microprocessor .mu.P1 without interrupting the
 switched connection.
 The microprocessor .mu.P1 is used for controlling the encoding unit K and
 the transmitting unit SEN1 as well as for selecting the encoding method
 and the video data depending on the request signals. The microprocessor
 .mu.P1 is connected to a memory MEMO1. In the memory MEMO1, there are
 stored the telephone numbers of the subscribers authorized to access the
 selection of video data in the video telephone TEL1. When the video
 telephone TEL1 is dialed up, then the microprocessor .mu.P1 checks if the
 telephone number of the caller is stored in memory or not. If the
 telephone number is stored in memory and the subscriber therefore is
 authorized to have access, then the video data are selected and the
 selected video data are transmitted. If the telephone number is not stored
 in memory, i.e. the authorization fails, then the subscriber receives a
 telephone message that access is denied.
 The video telephone TEL1 further comprises an audio unit AUD1. The audio
 unit AUD1 is used to encode the audio signals associated with a sequence
 of video images and to convey the encoded audio signals to the
 microprocessor .mu.P1. The audio signals are transmitted independently of
 the encoding method and are synchronized to the sequence of the video
 images. For example, the sequence is transmitted over the B1-channel while
 the audio signals are transmitted over the B2-channel.
 The encoding unit K and the audio unit AUD1 are connected to a camera CAM
 which records live, for example, a TV program.
 The video telephone TEL2 is used to transmit request signals and to receive
 video data and is connected to the video telephone TEL1 via the integrated
 services digital network NET.
 The video telephone TEL2 comprises a transmitting unit SEN2, a receiving
 unit EMP2, a control unit implemented as a microprocessor .mu.P2 and a
 memory MEMO2, wherein all the above elements are similar to the
 corresponding elements of video telephone TEL 1. The microprocessor .mu.P2
 is connected to a display screen BILD via a decoding unit D and to a
 loudspeaker via an audio unit AUD2.
 In the audio unit AUD2, the received signals are decoded and subsequently
 conveyed to the loudspeaker.
 The received video data are decoded in the decoding unit D and subsequently
 displayed on the display screen. The decoding unit D is switchable by the
 microprocessor .mu.P2 under software control. The received video data have
 to be decoded by the decoding unit D by the same method that was used for
 encoding the received video data. It is feasible to denote the encoding
 method by a bit in the header during transmission of the video data, or
 the decoding unit D is switched automatically for each transmitted
 selection number requesting a change in the encoding method.
 The video data and request signals between video telephone TEL1 and video
 telephone TEL2 are transmitted in a similar manner as between the server
 and the video telephone of FIG. 1, thus making a more detailed discussion
 redundant.
 The video telephone TEL2 further comprises an encoding unit K3 and a camera
 CAM integrated with the video telephone TEL2.
 The encoding unit K3 is similar to the encoding unit K of the video
 telephone TEL1.
 The encoder K2 which is controlled by the microprocessor .mu.P2, is capable
 of encoding, for example, a separate image of the subscriber. This encoded
 separate frame is stored in memory MEMO2. During the video telephone call
 between the subscriber with the video telephone TEL2 and a partner with
 another video telephone, the subscriber can, for example, select if the
 stored image should be used or if the live images from the camera CAM
 should be transmitted as a sequence of video data. The subscriber may
 during the switched connection also switch between the separate frame and
 a sequence of images. The stored image may, for example, depict a circuit
 diagram which is the topic of a discussion, or the like. The switching
 operation does not affect the transmission of the audio signals via the
 audio unit AUD2.
 In the embodiments, the encoding unit and the decoding unit can be switched
 between two encoding methods and two decoding methods, respectively.
 Instead of the encoding unit with two encoding methods, the invention can
 also be used with an encoding unit which can be switched between more than
 two, for example four, encoding methods. The first encoding method, for
 example, would encode video data in such a way that the data can only be
 transmitted over a 64 kbits/s line. The second encoding method, for
 example, would encode with twice the resolution, so that an encoded
 sequence of video images can be transmitted over a 128 kbits/s line. The
 third encoding method, for example, would encode with an even higher
 resolution, so that an encoded sequence of video images can be transmitted
 over a 2 Mbits/s line. In the forth encoding method, for example, separate
 frames would be encoded with a selectable resolution. The decoding unit is
 the counterpart of the encoding unit and is designed accordingly. Video
 telephones may also be designed with different decoding units. The
 decoding unit of a video telephone may, for example, be able to decode
 encoded video data transmitted over a 64 kbits/s line as well as encoded
 separate frames. The decoding unit of another video telephone may,
 conversely, be able to decode encoded video data transmitted over a 2
 Mbits/s line. Both video telephones would access the same server. The
 encoding unit in the video telephones may also be different, like the
 decoding units. This makes it possible to have video telephones with
 different features.
 In both embodiments, the encoding and decoding methods are selected by way
 of request signals entered by the subscriber on the keypad. Instead of
 entering the request signals manually via the keypad, the request signals
 may also be selected automatically, for example by a measuring unit in a
 video telephone which measures the transmission quality, deriving
 therefrom an appropriate encoding or decoding method, or by a unit for
 determining the available transmission bandwidth and establishing the
 suitable encoding method therefrom. This provides an additional feature
 for video telephones.