Abstract:
An apparatus for and method of storing video data comprising receiving an MPEG video stream comprising I-frames and P-frames, separating the I-frames from the P-frames, storing the I-frames and the P-frames separately, and providing information so that the I-frames and the P-frames can be combined to produce a full-motion video.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     N/A  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     N/A  
       BACKGROUND OF THE INVENTION  
       [0003]     This invention relates to surveillance systems and, in particular, to an apparatus for and method of storing video data in a video surveillance system.  
         [0004]     Archiving the video data gathered by video surveillance systems has been a challenge because of the large amount of data involved. In many instances this data may be stored for months or even years. With MPEG compression algorithms and the increased capacity of today&#39;s disk drives, the problem has been reduced, but it is far from being solved. In multi-channel applications, the storage problem is compounded by the number of channels.  
         [0005]     Current digital video recorders have two types of storage, namely, short-term and long-term. In most applications the short-term recordings are done with the maximum field rate to get full-motion video. All short-term available information is stored in a relatively small circular buffer. All video is stored at full-frame rate for the required period of time and then removed from the short-term buffer and put into another file for long-term storage. The file is either archived as originally recorded, which requires a large amount of long-term storage resources, or the file is processed to reduce the amount of data that is stored in archive. Processing the file before long-term storage requires that the file be reloaded and pruned in some way to provide a smaller file for archiving. This reloading and pruning process requires significant system resources and can seriously hamper the performance of the digital video recorder in recording current real time data and performing other real time operations.  
       SUMMARY OF THE INVENTION  
       [0006]     In accordance with the present invention there is provided a method of storing video data comprising the steps of receiving an MPEG video stream comprising I-frames and P-frames, separating the I-frames from the P-frames, storing the I-frames and P-frames separately, and providing information so that the I-frames and P-frames can be combined to produce a full-motion video.  
         [0007]     In accordance with the present invention there is also provided an apparatus for storing video data comprising an input for receiving an MPEG video stream comprising I-frames and P-frames, a video stream separator for separating the I-frames from the P-frames, memory for storing the I-frames and P-frames separately, and a sequence identifier for providing a unique identifier to the I-frames and P-frames so that the I-frames and P-frames can be combined to produce a full-motion video image.  
         [0008]     In another aspect of the present invention there is provided a method of searching stored video data comprising the steps of receiving an MPEG video stream comprising I-frames and P-frames, separating the I-frames and P-frames, storing the I-frames and P-frames separately, and searching only the stored I-frames.  
         [0009]     Another aspect of the present invention comprises an apparatus for searching stored video data comprising an input for receiving an MPEG video stream comprising I-frames and P-frames, a video stream separator for separating the I-frames and P-frames, memory for storing the I-frames and the P-frames separately, and a processor for searching only the stored I-frames.  
         [0010]     In still another aspect of the present invention there is provided a method of providing a fast playback video comprising the steps of: receiving an MPEG video stream comprising I-frames and P-frames, separating the I-frames and P-frames; storing the I-frames and P-frames separately; and playing back only the stored I-frames in the fast playback mode.  
         [0011]     In addition, in accordance with the present invention there is provided an apparatus for providing a fast playback video comprising an input for receiving an MPEG video stream comprising I-frames and P-frames; a video stream separator for separating the I-frames and P-frames; memory for storing the I-frames and P-frames separately; and a processor for playing back only the stored I-frames during fast playback mode.  
         [0012]     Applicant&#39;s invention provides efficient preprocessing of the video data so that archiving of the video data is accomplished efficiently. Applicant&#39;s system provides full-motion video for the required time period and then allows easy archiving of the I-frame file by merely changing the file name, if desired, and placing it in archival storage. No reprocessing and interruption of the normal processing of the digital video recorder is required. By saving only the I-frames. The present invention eliminates up to eighty percent of the data to provide a significant savings advantage on long-term storage. Applicant&#39;s system can also utilize two circular buffers having different periods of time before data is overwritten with new data, thereby providing the possibility of full-motion video during the shorter period of time that the P-frame data is held and providing for the longer term storage of the second circular buffer containing the I-frames.  
         [0013]     Applicant&#39;s invention also provides an efficient method to search video data and provide fast playback without burdening system resources.  
         [0014]     Other advantages and applications of the present invention will be made apparent by the following detailed description of the preferred embodiment of the invention. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0015]      FIG. 1  is a block diagram of a digital video recorder utilizing the present invention.  
         [0016]      FIG. 2  is a diagrammatic block diagram illustrating the processing of an MPEG stream according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     Referring to  FIG. 1 , a digital video recorder  10  receives an MPEG video stream  28  at input  12 , which provides MPEG video stream  28  to processor  14 . MPEG video stream  28  can be provided via a closed network, local area network or wide area network, such as the Internet. Processor  14  is connected to ROM  16 , RAM  18 , and storage  20 , which can be, for example, a disk drive or optical drive. Processor  14  provides output signals to output  24  for display on a monitor (not shown). Processor  14  implements algorithms and programs that are stored in ROM  16  or storage  20 . User input device  26  can be a controller, keyboard, or other suitable input device connected directly to digital video recorder  10 , or user input device  26  can be connected via a, network, which can be a closed network, local area network or wide area network, such as the Internet. User input device  26  provides user input to processor  14 , such as instructions to begin or stop recording video data, play video data, search video data, playback video data in fast playback mode, and so forth.  
         [0018]      FIG. 2  illustrates an exemplary MPEG stream  28  that consists of a series of data frames encoding pictures. The three types of data frames are I-frames, P-frames, and B-frames. I-frames are encoded as a single image with no reference to any past or future frames. P-frames (predictive) are encoded relative to the past reference frame, which can be a P-frame or I-frame. The past reference frame is the closest preceding reference frame. B-frames (bidirectional predictive) are encoded relative to the past reference frame, the future reference frame, or both frames. The future reference frame is the closest following reference frame, either I-frame or P-frame. The series of frames, which is referred to in the art as a Group of Pictures (GOP), can take many different configurations, and, as stated above, MPEG video stream  28  is merely exemplary. The ratio of I-frames, P-frames, and B-frames is determined by the nature of the video stream and the bandwidth constraints of the network and system. In addition, the time required for encoding the video stream may also affect the ratio. MPEG video stream  28  is shown as having B-frames, although an MPEG stream consisting of only I-frames and P-frames has been found to be satisfactory for video surveillance system purposes.  
         [0019]     With reference to  FIG. 1  and  FIG. 2 , MPEG stream  28  is separated by processor  14  into two separate files, file  30  and file  32 . Alternatively, other circuitry could be used as a video stream separator. Processor  14  determines the frame type by examining the frame headers. File  30  contains only I-frames, and file  32  contains P-frames and B-frames. As discussed above, MPEG stream  28  may not contain B-frames, and thus file  32  would contain only P-frames. Files  30  and  32  each have a unique identifier, which can be in the header of the respective files and can be a unique time stamp provided by processor  14 . Processor  14  also provides each frame with a sequential frame number, (indicated as  1  through  10  in  FIG. 2 ) so that files  30  and  32  can be combined by processor  14  to provide full-motion video in response to a request from user input device  26 .  
         [0020]     Files  30  and  32  can be stored in storage  20 , which can be partitioned into short-term and long-term storage areas. The short-term and long-term storage areas can be circular buffers. The size of the two circular buffers depends on the amount of data to be stored and the length of time to keep the data before it is overwritten with new data. Alternatively, file  30  can be placed in long-term storage for archival purposes or held in an interim storage area prior to placing in long-term storage. File  32  is temporarily saved so that full-motion video can be provided by output  24  to a display for viewing for the required period of time to meet the purposes and policies of the surveillance system in which digital video recorder  10  is utilized. Processor  14  determines when the specified time has elapsed, whether it be hours, days, or longer, and then allows file  32  to be overwritten with new data. If file  32  is stored in a circular buffer, file  32  is stored there and then overwritten automatically without processor  14  monitoring the elapsed time. Similarly, file  30  can be placed in a circular and overwritten automatically. The time period between the storing of the data in the circular buffers until it is overwritten is greater for file  30  than it is for file  32 . Short-term storage may be, for example, one to two weeks, and long-term storage may be, for example, six months. If desired, file  32  can be placed into long-term storage to provide full-motion video capability. File  32  can then be easily disposed of by overwriting it with other data or simply deleting if without affecting the I-frames which may be kept for archival purposes.  
         [0021]     Digital video recorder  10  provides a savings of up to eighty percent of the space required for archival storage by storing only file  30  with the I-frames. Nevertheless, digital video recorder  10  still provides full-motion video capability during the period of time that such video may be of interest to the user. In addition, digital video recorder  10  does not require processor  14  to reload and process MPEG stream  28  before the data is archived as is required by a system that stores MPEG stream  28  as it is received by input  12 .  
         [0022]     If desired, prior to archival storage, file  30  can be processed by processor  14  so that only a portion of file  30  is placed into archival storage in storage  20 . For example, a first I-frame may be stored, then one or more I-frames can be skipped and then the next I-frame is recorded. This process is repeated until all of file  30  has been processed. Processing file  30  to remove a portion of the I-frames is a relatively simple and efficient operation compared to reloading and reprocessing of the entire MPEG stream, thereby placing only a minimal demand on system resources.  
         [0023]     If processor  14  receives a request to search the recorded video data, processor  14  executes the search using only file  30  to expedite the search and limit system resource requirements compared to a system that stores MPEG stream  28  as it is received by input  12 . Similarly, if processor  14  receives a request to playback the recorded video data in fast playback mode, processor  14  provides the fast playback mode by playing only file  30 . This provides a significant savings in the system resources required to display the recorded video data in fast playback mode compared to a system that stores MPEG stream  28  as it is received by input  12 .  
         [0024]     It is to be understood that variations and modifications of the present invention can be made without departing from the scope of the invention. It is also to be understood that the scope of the invention is not to be interpreted as limited to the specific embodiments disclosed herein, but only in accordance with the appended claims when read in light of the foregoing disclosure.