Abstract:
A feedback path to the processor for a video signal in a computer. The video image data is not normally subjected to benchmark testing because it would make it susceptible to illegal copying. The digital video output signal is sent back to the processor one pixel at a time, with a delay between pixels equivalent to one line time. The result is that the pixel feed is so slow that digital copying is impractical. A lockout timer allows the pixel data to be sent to the processor only at intervals.

Description:
FIELD 
     The present invention is directed to a computer system having benchmark testing of the video signal and, more particularly, to a computer system having a feedback path for benchmark testing of the video signal while preventing illegal copying. 
     BACKGROUND 
     Computer systems are now in use which use benchmark programs to analyze the performance of the graphics function in the graphics controller. Thus, these benchmarks measure the speed and accuracy of the generated graphics on a three-dimensional basis. Such a system contains elements shown in FIG.  1 . Computer system  10  includes a central processing unit  12  and a memory  14  which are interconnected. It also includes a graphics controller  16  which generates and controls the graphics which are displayed in monitor  18 . The device also includes a frame buffer  20  which receives the graphics signal before display on the monitor  18 . The frame buffer  20  is also connected to the processor  12  so that the graphics signal may be measured by the processor  12  and a programmed benchmarked system can be used to determine the speed and accuracy of the graphics signal. 
     In addition to the traditional graphics information to be displayed, computers also now have the ability of displaying video signals. This may be a video signal stored in memory, it may be a video signal which is received over an internet connection and stored in memory for later play or it may be a video signal received from a DVD ROM. Such signals whether played directly or stored in the memory for later play are handled differently than the graphics signals. An overlay block  22  is provided within the graphics controller  16  to receive and combine both the graphics and video signals. However, the video signal is not directly accessible by the processor  12  and, accordingly, it is not possible to perform a benchmark testing operation on the video signal. This means that it is not possible for the processor  12  to adjust the video signal to enhance its displayed appearance. It also does not provide a manner of testing the functionality of the system and so compare it to other systems. 
     The overlay block  22  reads video image data from the memory  14 , scales the image and color converts the data for presentation to the digital-to-analog converter. However, this is no feedback path to the memory  14  or to the processor  12  from the overlay block  22 . Thus, the overlay image data cannot be observed except on the monitor  18 . 
     The main reason that this signal is not included in a feedback path is to make it more difficult to illegally copy the video signal. For example, if the video material is taken from a DVD ROM, the original provider of the ROM does not wish the signal to be available for illegal duplication. If the video signal were fed back to the processor  12  it would more likely be copied. By keeping the video signal hidden, illegal copying is extremely difficult. Unfortunately, it also makes it extremely difficult to perform benchmark testing to measure the quality of the video signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and a better understanding of the present system will become apparent from the following detailed description of example embodiments and the claims when read in connection with the accompanying drawings, all forming a part of the disclosure. While the foregoing and following written and illustrated disclosure focuses on disclosing example embodiments of the system, it should be clearly understood that the same is by way of illustration and example only and the system is not limited thereto. The spirit and scope of the present invention are limited only by the terms of the appended claims. 
     The following represents brief descriptions of the drawings, wherein: 
     FIG. 1 shows an example disadvantageous computer system into which the present embodiment may be placed. 
     FIG. 2 is a schematic diagram showing the video overlay of FIG. 1 incorporating an example embodiment. 
    
    
     DETAILED DESCRIPTION 
     Before beginning a detailed description of the subject system, mention of the following is in order. When appropriate, like reference numerals and characters may be used to designate identical, corresponding or similar components in differing figure drawings. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to FIG. 2 thereof, which show the overlay block  22  of the present embodiment. As in the prior art, the overlay block  22  receive the video image data and the graphics image data. As in the prior art, the video processing functions  24  and chroma keying  26  operate on the video and graphics image data and prepare the signal for output to a monitor  18 . Before outputting the signal, the digital signal is converted to an analog signal in RGB digital-to-analog converter  28 . The analog signals is are output to monitor  18  for display. A pixel counter  30  and line counter  32  are also present to keep track of the particular position of the displayed pixel in the video image. The pixel counter  30  and line counter  32  provide an indication of a position of the CRT beam during that particular pixel. 
     In addition to this structure which is normally present in an overlay block of the prior art, the present embodiment may provide additional structure to allow the video signal to be sent back to the processor for benchmark testing. A digital signal is taken from the input to the digital-to-analog converter  28  and held in pixel holding register  40 . Once the pixel is ready to be read out of the pixel holding register  4 Q, the pixel holding register  4 Q sends a pixel ready status signal to the processor. Alternatively, this could be in the form of an interrupt signal or polled status arrangement. When the processor is ready to test the pixel signal, a read command is sent from the processor to the pixel holding register  40 . The pixel data is then sent to the processor for benchmark testing. 
     A pixel position comparator  42  is also provided which receive the position of the displayed pixel from the pixel counter  30  and line counter  32 . This actual position is compared with a pixel selection data signal from the processor which requests data from a particular selected pixel. When the pixel position comparator  42  finds a match, a signal is then sent to pixel holding register  40  to sample the digital signal at that point. The processor will select pixels in some type of sequence so that the entire picture is tested over a period of time. 
     As indicated above, however, there is a problem in the industry that the providers of video material do not want the video signal available for copying. By sending this pixel data to the processor, it makes it much easier for the video signal to be illegally copied. In order to make this pixel data unusable for copying, applicants have provided a lockout timer circuit  44  which receive the read command signal from the processor as it is sent to the pixel holding register  40 . Upon receipt of the read command, the lockout timer circuit  44  will produce one enabling signal to allow the pixel position comparator  42  to forward the sampling signal to the pixel holding register  40 . Alternatively, this enabling signal could go directly to the pixel holding register  40 . In either case, the enabling signal allows the pixel signal to be read and forwarded to the processor. 
     The lockout timer circuit  44  includes a clock which then prohibits the lockout timer circuit  44  from forwarding another enable signal for a set amount of time. For example, an enabling signal can be produced at the end of each line of the video display. Since the video image is typically 720 pixels wide, this would mean that it would require passing 720 lines of video image to sample across a single line. Normally, if the video image is introduced at 60 Hz, it would then take 12 seconds to capture an entire video image. For the video quality analysis program, this spread of time is not too prohibitive. Thus, the processor could do a benchmark check every 12 seconds on an image which is fast enough to produce measurements and to control the quality of the video signal. However, this is slow enough that an illegal copier would be deterred from trying to steal the video signal. For example, if a DVD movie is played, it would take about 792 hours (33 days) to capture the entire movie in the decoded format. This is slow enough that copying is deterred. 
     While the enable signal from the lockout timer circuit  44  is correlated to the passage of a line of video image, it is also possible to utilize a time passage of a greater or lesser size. However, the size must be such that the capture of the video signal is slow enough to deter illegal copies. The time can be determined by an internal clock, or if it is correlated to an end-of-line signal or other internal signal, it could be taken directly from this signal. 
     Once the pixel data has been sent to the processor, it is possible to utilize an algorithm to measure different parameters of the video signal according to any number of performance measuring benchmark algorithms already available. For example, the video signal can be measured according to an algorithm called “Just Noticeable Difference” by the Sarnoff Corporation. Benchmark measuring programs determine not only the speed of the video, such as the number of frames per second and how fast it can draw circles, but also can now look at the quality of the picture itself to determine if it is fuzzy, if the colors are correct, whether there is accuracy in the decompression of the data and other quality performance benchmarks. This data can be used either for analysis and improvement of the circuit or it can be used directly in a feedback arrangement to control the video settings so as to improve the picture. 
     This concludes the description of the example embodiments. Although the present system has been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention. More particularly, reasonable variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the foregoing disclosure, the drawings and the appended claims without departing from the spirit of the invention. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art. 
     Further, in the detailed description to follow, example sizes/models/values/ranges may be given, although the present system is not limited to the same. As a final note, well known power/ground connections to ICs and other components may not be shown within the figures for simplicity of illustration and discussion, and so as not to obscure the invention. Further arrangements may be shown in block diagram form in order to avoid obscuring the invention, and also in view of the fact that specifics with respect to implementation of such block diagram arrangements is highly dependent upon the platform within which the present invention is to be implemented, i.e., specifics should be well within purview of one skilled in the art. Where specific details (e.g., circuits, flowcharts) are set forth in order to describe example embodiments, it should be apparent to one skilled in the art that the invention can be practiced without these specific details. Finally, it should be apparent that any combination of hard-wired circuitry and software instructions can be used to implement embodiments of the present invention, i.e., the present invention is not limited to any specific combination of hardware circuitry and software instructions. 
     Although example embodiments of the present invention will be described using an example system block diagram in an example personal computer (PC) environment, practice of the invention is not limited thereto, i.e., the invention may be able to be practiced with other types of systems, and in other types of environments (e.g., servers). 
     Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.