Abstract:
An image processing apparatus includes a reception unit, a decoding unit, a sub frame generating unit and an image signal generating unit. The reception unit receives at least three encoded image data via a serial bus. The decoding unit decodes one of the received encoded image data to generate a main frame. The sub frame generating unit extracts low frequency component from each one of the other received encoded image data, and generates sub frames from the extracted low frequency components. The image signal generating unit combines the main frame and the sub frames, and generates an image signal including the main frame combined with the sub frames.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system for receiving plural digital images in an encoded state and displaying the plural images in a same frame. 
     2. Related Background Art 
     Recently there are developed technologies of transmitting and receiving digital image data, encoded and recorded in a recording medium, in such encoded state. One of the standards realizing such technologies is the IEEE1394-1995 standard. 
     The IEEE1394-1995 standard is one of the standards realizing a high performance serial bus, and is provided with a transfer method called isochronous transfer method. The isochronous transfer method guarantees data transfer of a predetermined size for each communication cycle (one communication cycle being about 125 μsec, and is suitable for transmission and reception of data for which the real time character is important, such as image data or audio data. Also the isochronous transfer method does not specify the designation. Therefore, a packet transferred by the isochronous transfer method (hereinafter called isochronous packet) from a node is broadcast over the entire serial bus. The isochronous packets transferred from plural nodes are managed by channel numbers 0 to 63. Also the isochronous packets transferred from the plural nodes are broadcast on time-shared basis in every communication cycles. 
     The DV standard defined by the HD Digital VCR Conference takes the isochronous transfer method of the IEEE1394-1995 standard into consideration and adopts the IEEE1394-1995 standard for the digital interface of the digital video cassette recorder. 
     However, in a system for receiving the plural digital image data in encoded state through a digital interface based on the IEEE1394-1995 standard and displaying such plural images on a same image frame, the conventional configuration requires plural decoders and plural frame memories in parallel. There are associated drawbacks of a larger hardware of the system and a higher manufacturing cost thereof. 
     SUMMARY OF THE INVENTION 
     In consideration of the foregoing, the object of the present invention is to provide an image processing apparatus and an image processing method not requiring plural decoders or plural frame memories even in case of receiving the plural digital image data in encoded state and displaying these images on a same frame. 
     The above-mentioned object can be attained, according to a preferred embodiment of the present invention, by an image processing apparatus comprising: 
     reception means for receiving plural image data; 
     main frame generation means for decoding one of the plural image data to generate a main frame; 
     sub frame generation means for extracting a low frequency component from one of the plural image data to generate a sub frame; and 
     output means for outputting an image signal including the main frame and the sub frame. 
     According to another embodiment of the present invention, there is also provided an image processing method comprising steps of: 
     receiving plural image data; 
     decoding one of the plural image data to generate a main frame; 
     extracting a low frequency component from one of the plural image data to generate a sub frame; and 
     outputting an image signal including the main frame and the sub frame. 
     Other objects of the present invention, and the advantages thereof, will become fully apparent from the following detailed description of the embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing the principal configuration of an image recording apparatus  100  embodying the present invention; 
         FIG. 2  is a view showing an example of a display frame generated by the image recording apparatus  100  embodying the present invention; and 
         FIG. 3  is a view showing a procedure of switching images displayed by a main frame  301  and sub frames  302 - 1  to  302 -(N−1). 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention will now be described in detail hereinafter with reference to the accompanying drawings. 
       FIG. 1  is a view showing the principal configuration of an image recording apparatus  100  embodying the present invention, and  FIG. 2  is a view showing an example of the display image frame generated by the image recording apparatus  100  embodying the present invention. 
     Image devices  200 - 1  to  200 -N (N is two or more integer), after acquiring channel numbers and bands required for isochronous transfer, generate plural isochronous packets including digital image data according to the SD format of the DV standard (such data being hereinafter called SD data) and transmit each isochronous packet in each communication cycle (about 125 μsec) to the image recording apparatus  100 . 
     Serial bus  10  is a serial bus based on IEE1394-1995 standard. An IEEE1394 interface  12 , based on the IEEE1394-1995 standard, receives an isochronous packet transmitted in each communication cycle from the image device  200 - 1  to  200 -N, and sends such packets respectively to isochronous packet processing units  14 - 1  to  14 -N. Each of the isochronous packet processing units  14 - 1  to  14 -N extracts SD data from each isochronous packet and sends such data to a sub frame generation unit  16 . 
     The sub frame generation unit  16  selects an isochronous packet processing unit  14 - x  (x being one of 1 to N) according to an instruction from a display control unit  18 , and writes the SD data, outputted from such selected unit, into a track memory  20 . Also the sub frame generation unit  16  extracts the DC components of digital image data from SD data outputted from the isochronous packet processing units  14 - 1  to  14 -N (excluding the isochronous packet processing unit  14 - x ), and generates sub frames  302 - 1  to  302 -(N−1) utilizing thus extracted components. In the SD format of the DV standard, the DC component can be easily extracted since the DC components of the luminance data and the color difference data are positioned in predetermined data areas. The sub frames  302 - 1  to  302 -(N−1) generated in the sub frame generation unit  16  are written in memories  22 - 1  to  22 -(N−1). 
     A decoder  26  entirely decodes the SD data read from the track memory  20 , thereby generating a main frame  301  as shown in  FIG. 2 . The main frame memory  301  generated by the decoder  26  is written into a frame memory  32 . 
     A writing control unit  304  reads the sub frames  302 - 1  to  302 -N from the memories  22 - 1  to  22 -(N−1) respectively and overwrites such sub frames on a main frame  301  stored by frame memory  32 . In addition, each of such sub frames  302 - 1  to  302 -(N−1) is overwritten into predetermined memory areas (at the right hand side of the main frame  301  in the present embodiment) on the main frame  301 . The position or size of the sub frames  302 - 1  to  302 -(N−1) may be altered by the writing control unit  304  by changing the position or size of the memory areas corresponding to the sub frames  302 - 1  to  302 -(N−1). 
     An image processing unit  36  reads digital image data (including the main frame  301  and sub frames  302 - 1  to  302 -(N−1)) of a frame from the frame memory  32  for each frame and converts the image data into an analog image signal. The analog image signal generated in the image processing unit  36  is outputted to the exterior through an image output terminal  40 . A display device  38  enters and displays the analog image signal outputted from the image output terminal  40 . Thus, on the display device  38 , the digital image data transmitted from one of the plural image devices  200 - 1  to  200 -N is displayed in a large scale on the main frame  301  and the digital image data transmitted from other image devices are displayed in the sub frames  302 - 1  to  302 -(N−1) smaller than the main frame  301 . 
     In case of switching the image displayed on the main frame  301 , the user instructs the switching of the display by rotating a display switching key  42  by a predetermined amount. In response to the rotation of the display switching key  42  by the predetermined amount, the display control unit  18  controls the sub frame generation unit  16  in such a manner as to switch the images displayed on the main frame  301  and the sub frames  302 - 1  to  302 -(N−1). For example, whenever the display switching key  42  is rotated to left side, the display control unit  18  controls display as follows. The switching is so executed as to display the image, which has been displayed on the main frame  301 , in the sub frame  302 -(N−1), to display the image, which has been displayed on the sub frame  302 - 1 , on the main frame  301 , and to display the image, which has been displayed in the sub frame  302 - 2 , in the sub frame  302 - 1 . On the other hand, whenever the display switching key  42  is rotated right side, the display control unit  18  controls the switching as to display the image, which has been displayed on the main frame  301 , in the sub frame  302 - 1  and to display the image, which has been displayed on the sub frame  302 -(N−1), in the main frame  301 . 
     In case an image is to be recorded, the user rotates the display switching key  42  until the image to be recorded is displayed on the main frame  301 . After the image to be recorded is displayed on the main frame  301 , the user instructs the start of recording by depressing a recording start key  44 . In response to the depression of the recording start key  44 , a recording unit  24  records the SD data, held in the track memory  20 , on a recording medium  30 , which can for example be a magnetic tape, a magnetic disk, a hard disk, a semiconductor memory or the like. 
     As explained in the foregoing, the image recording apparatus  100  of the present embodiment does not require plural decoders nor plural frame memories even in case of receiving plural digital image data in the encoded state and displaying such digital image data on a same frame, thereby enabling simplification of the circuit configuration, reduction in the manufacturing cost and reduction in the electric power consumption. 
     Also the image recording apparatus  100  of the present embodiment allows to simply select the image to be recorded, since the recording of the image displayed on the main frame  301  can be started by merely depressing the recording start key  33  and also since the image displayed on the main frame  301  can be switched by merely rotating the display switching key  42 . 
     The invention may be embodied in other specific forms without departing from essential characteristics thereof. 
     In the forgoing embodiment, there has been explained a case of handling the digital image data encoded according to the SD format of the DV standard, but the present invention is not limited to such case. It is likewise applicable to the digital image data encoded according to the SDL format or HD format of the DV standard, or according to the Motion JPEG-2000 standard. 
     Also in the foregoing embodiment, there has been explained a case where the sub frames are arranged at the right hand side of the main frame, but the present invention is not limited to such case. It is likewise applicable to a case where the sub frames are arranged in positioned not at the right hand side of the main frame (for example at the lower side thereof), or a case where the sub frames are provided in positioned designated in advance by the user. 
     Also in the foregoing embodiment, there has been explained a case where the image recording apparatus  100  and the image devices  200 - 1  to  200 -N are connected through a digital interface based on the IEEE1394-1995 standard, but the present invention is not limited to such case. It is likewise applicable to a case where the image recording apparatus  100  and the image device  200 - 1  to  200 -N are connected through a digital interface based on an expansion of the IEEE1394-1995 standard (for example IEEE1394a-2000 standard or IEEE1394.b standard). 
     Also in the foregoing embodiment, there has been explained a case where the display switching key  42  and the recording start key  44  are provided separately, but the present invention is not limited to such case and is likewise applicable to a case where the display switching key  42  and the recording start key  44  are formed integrally. 
     Moreover, in this embodiments, the case where the sub frames  302 - 1  to  302 -(N−1) are generated only using DC component is explained. However, the present invention is not restricted to this case. It is possible to apply to the case where the sub frames  301 - 1  to  302 -(N−1) are generated using a part of DC component and AC component. 
     Therefore, the above-mentioned embodiments are merely examples in all respects, and must not be construed to limit the invention. 
     The scope of the present invention is defined by the scope of the appended claims, and is not limited at all by the specific description of this specification. Furthermore, all the modifications and changes belonging to equivalents of the claims are considered to fall within the scope of the present invention.