Abstract:
An image processing method for frame rate conversion, comprising: receiving a stream of input pictures at an input frame rate, at least some of the input pictures being new pictures, the new pictures appearing within the stream of input pictures at an underlying new picture rate; generating interpolated pictures from certain ones of the input pictures; outputting a stream of output pictures at an output frame rate, the stream of output pictures including a blend of the new pictures and the interpolated pictures, the interpolated pictures appearing in the stream of output pictures at an average interpolated picture rate; and causing a variation in the average interpolated picture rate in response to detection of a variation in the underlying new picture rate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE 
       [0001]    This patent application makes reference to, claims priority to and claims benefit from U.S. Provisional Patent Application Ser. No. 61/071,470 filed on Apr. 30, 2008. 
         [0002]    The above stated application is hereby incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0003]    Certain embodiments of the invention relate to image processing. More specifically, certain embodiments of the invention relate to image processing methods and systems for frame rate conversion. 
       BACKGROUND OF THE INVENTION 
       [0004]    Excellent motion portrayal is a strong characteristic of cathode ray tubes (CRTs) whereas it is a weakness in many pixelized displays. In particular, motion blur is a limitation of many liquid crystal displays (LCDs). Motion blur in LCDs is caused by various phenomena, one of which is the sample and hold principle of the LCD. Motion blur can be subjectively reduced by modulating the backlight of the display. However, this can introduce flicker. Another option for subjectively reducing motion blur is to increase the frame rate, known as frame rate conversion. This typically relies on a process known as temporal interpolation to create one or more new pictures for placement between two original pictures. 
         [0005]    An input video signal whose frame rate is to be increased can consist of several segments of pictures originally taken using video, film and/or other media. For regular video content, which is characterized by the fact that every picture originates at a different moment in time, a 60 Hz input signal can be converted to, say, 120 Hz by placing a single interpolated picture temporally in the middle position between neighboring pictures in the input video signal. However, the situation is different for film material, as film is captured at 24 Hz and (for 60 Hz countries) up-converted by a 3:2 pull down cadence to give a 60 Hz signal. Simply placing a single interpolated picture between each picture of the 3:2 pull down 60 Hz signal to give a resulting output signal at the desired frame rate of 120 Hz would not lead to motion blur reduction at all, and the motion portrayal remains highly irregular in the output signal. 
         [0006]    Thus, for film material, motion judder of the film cadence needs to be eliminated prior to up-conversion. This basically means that the 24 Hz original film material is up-converted to 120 Hz by placing  4  new interpolated pictures between neighboring 24 Hz original pictures. Since 80% of the output video now consists of interpolated pictures, the demands of the interpolator are increased. Moreover, perceived picture quality can be severely degraded due to the high proportion of time occupied by interpolated rather than original pictures. 
         [0007]    Against this background, there is a need in the industry for a method and system for frame rate conversion based on temporal interpolation, but with improved picture quality and greater computational efficiency than conventional techniques. 
         [0008]    Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    According to a first aspect, the present invention seeks to provide an image processing method for frame rate conversion, comprising: receiving a stream of input pictures at an input frame rate, at least some of the input pictures being new pictures, the new pictures appearing within the stream of input pictures at an underlying new picture rate; generating interpolated pictures from certain ones of the input pictures; outputting a stream of output pictures at an output frame rate, the stream of output pictures including a blend of the new pictures and the interpolated pictures, the interpolated pictures appearing in the stream of output pictures at an average interpolated picture rate; and causing a variation in the average interpolated picture rate in response to detection of a variation in the underlying new picture rate. 
         [0010]    According to a second aspect, the present invention seeks to provide a computer-readable storage medium comprising computer-readable instructions for instructing a computing device to: receive a stream of input pictures at an input frame rate, at least some of the input pictures being new pictures, the new pictures appearing within the stream of input pictures at an underlying new picture rate; generate interpolated pictures from certain ones of the input pictures; output a stream of output pictures at an output frame rate, the stream of output pictures including a blend of the new pictures and the interpolated pictures, the interpolated pictures appearing in the stream of output pictures at an average interpolated picture rate; and cause a variation in the average interpolated picture rate in response to detection of a variation in the underlying new picture rate. 
         [0011]    According to a third aspect, the present invention seeks to provide a computer-readable storage medium comprising computer-readable instructions which when processed are used to generate a processor/apparatus adapted to: receive a stream of input pictures at an input frame rate, at least some of the input pictures being new pictures, the new pictures appearing within the stream of input pictures at an underlying new picture rate; generate interpolated pictures from certain ones of the input pictures; output a stream of output pictures at an output frame rate, the stream of output pictures including a blend of the new pictures and the interpolated pictures, the interpolated pictures appearing in the stream of output pictures at an average interpolated picture rate; and cause a variation in the average interpolated picture rate in response to detection of a variation in the underlying new picture rate. 
         [0012]    According to a fourth aspect, the present invention seeks to provide an image processing engine adapted to implement a frame rate conversion process that comprises: receiving a stream of input pictures at an input frame rate, at least some of the input pictures being new pictures, the new pictures appearing within the stream of input pictures at an underlying new picture rate; generating interpolated pictures from certain ones of the input pictures; outputting a stream of output pictures at an output frame rate, the stream of output pictures including a blend of the new pictures and the interpolated pictures, the interpolated pictures appearing in the stream of output pictures at an average interpolated picture rate; and causing a variation in the average interpolated picture rate in response to detection of a variation in the underlying new picture rate. 
         [0013]    According to a fifth aspect, the present invention seeks to provide an image an image processing method for frame rate conversion, comprising: receiving a stream of first pictures at a first frame rate; generating interpolated pictures from the first pictures; outputting a stream of output pictures at an output frame rate, the stream of output pictures including a blend of the first pictures and the interpolated pictures, the interpolated pictures appearing in the stream of output pictures at an average interpolated picture rate; processing the first pictures to determine a likelihood of interpolation induced artifacts in the output pictures; adjusting the average interpolated picture rate based on said likelihood. 
         [0014]    According to a sixth aspect, the present invention seeks to provide a computer-readable storage medium comprising computer-readable instructions for instructing a computing device to: receive a stream of first pictures at a first frame rate; generate interpolated pictures from the first pictures; output a stream of output pictures at an output frame rate, the stream of output pictures including a blend of the first pictures and the interpolated pictures, the interpolated pictures appearing in the stream of output pictures at an average interpolated picture rate; process the first pictures to determine a likelihood of interpolation-induced artifacts in the output pictures; and adjust the average interpolated picture rate based on said likelihood. 
         [0015]    According to a seventh aspect, the present invention seeks to provide a computer readable storage medium comprising computer-readable instructions which when processed are used to generate a processor/apparatus adapted to: receive a stream of first pictures at a first frame rate; generate interpolated pictures from the first pictures; output a stream of output pictures at an output frame rate, the stream of output pictures including a blend of the first pictures and the interpolated pictures, the interpolated pictures appearing in the stream of output pictures at an average interpolated picture rate; process the first pictures to determine a likelihood of interpolation-induced artifacts in the output pictures; and adjust the average interpolated picture rate based on said likelihood. 
         [0016]    According to an eighth aspect, the present invention seeks to provide an image processing engine adapted to implement a frame rate conversion process that comprises: receiving a stream of first pictures at a first frame rate; generating interpolated pictures from the first pictures; outputting a stream of output pictures at an output frame rate, the stream of output pictures including a blend of the first pictures and the interpolated pictures, the interpolated pictures appearing in the stream of output pictures at an average interpolated picture rate; processing the first pictures to determine a likelihood of interpolation induced artifacts in the output pictures; and adjusting the average interpolated picture rate based on said likelihood. 
         [0017]    These and other aspects and features of the present invention will now become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         [0018]      FIG. 1  is a block diagram showing an image processing engine in accordance with a non-limiting embodiment of the present invention. 
           [0019]      FIG. 2  is a flowchart that illustrates steps in a frame rate conversion process that can be executed by an image processing engine, in accordance with a non-limiting embodiment of the present invention. 
           [0020]      FIG. 3  is a conceptual diagram illustrating the frame rate conversion process in accordance with a non-limiting embodiment of the present invention, whereby a stream of input pictures is converted into a stream of output pictures. 
           [0021]      FIGS. 4A-4C  show details of the effect of the frame rate conversion process in accordance with non-limiting embodiments of the present invention when the rate of output pictures is caused to vary. 
           [0022]      FIGS. 5A and 5B  show details of the effect of the frame rate conversion process in accordance with non-limiting embodiments of the present invention when the rate of output pictures is caused to remain the same. 
       
    
    
       [0023]    It is to be expressly understood that the description and drawings are only for the purpose of illustration of certain embodiments of the invention and are an aid for understanding. They are not intended to be a definition of the limits of the invention. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Reference is made to  FIG. 1 , which shows an image processing engine  100  adapted to receive an input picture stream  102  from an image source  130  such as a picture buffer. The input picture stream  102  comprises a sequence of input pictures  104  at an input frame rate FR in  in pictures per time unit (e.g., pictures per second, hereinafter abbreviated as “pps”). Among the input pictures  104 , at least some of them are “new”, while others may be non-new (or “repeated”). By a particular input picture being “new” it is meant that the particular input picture was captured at a unique instant in time. It should be appreciated that in some cases, all of the input pictures  104  in the input picture stream  102  may be new while in other cases two of the input pictures  104 , say X and Y, can indeed be new but either X or Y is repeated once (or a greater number of times) and positioned between X and Y in the input picture stream  102 . The image processing engine  100  receives the input picture stream  102  and produces therefrom an output picture stream  106 , comprising a sequence of output pictures  108  at an output frame rate FR out  in pictures per time unit (e.g., pps). The output picture stream  106  can be rendered on a display  120 . 
         [0025]    In one non-limiting embodiment, the image processing engine  100  can be implemented in an application-specific integrated circuit (ASIC) such as can be integrated into a television set, computer graphics processor or other electronic device. In another non-limiting embodiment, the image processing engine  100  can be implemented by programmable elements of a computing device such as a personal computer, mobile computer or mobile communication device. Other implementations will be apparent to those of skill in the art as being within the scope of the present invention. 
         [0026]    The image processing engine  100  is configured to implement a frame rate conversion process  200 , which can be viewed as a sequence of steps, some of which will now be described with additional reference to  FIG. 2 . It should be appreciated that in the present specification, the words “picture” and “frame” are used interchangeably. 
         [0027]    At step  202 , the image processing engine  100  is configured to determine, on an ongoing basis, which of the input pictures  104  are new and also to determine their rate in pictures per time unit (e.g., pps), which can be referred to as an underlying new picture rate and is hereinafter denoted NFR in . Step  202  can be executed in a variety of ways, including implementing a cadence detection process such as that provided by the ABT2010 video processing chip available from Anchor Bay Technologies, Los Gatos, Calif. For the sake of notational convenience, those of the input pictures  104  found to be new are denoted  104 *. 
         [0028]    At step  204 , the image processing engine  100  is configured to determine a suitable value of the output frame rate FR out  that depends on a variety of factors. For example, in one embodiment, the value of the output frame rate FR out  depends on the underlying new picture rate NFR in  as a function of a pre-determined mapping. This mapping could quite simply indicate that the output frame rate FR out  is related to the underlying new picture rate NFR in  by an increasing function, such that increases in the underlying new picture rate NFR in  will result in increases in the output frame rate FR out , while decreases in the underlying new picture rate NFR in , will result in decreases in the output frame rate FR out . In a second example embodiment, the output frame rate FRout may be constrained to retain the same value during times where the underlying new picture rate NFR in , may undergo transitions. In this case, there is no actual mapping between the underlying new picture rate NFR in  and the output frame rate FR out . 
         [0029]    At step  206 , the image processing engine  100  computes a number (“R”) of interpolated pictures  110   1 . . . R  for each of the new input pictures  104 *. The interpolated pictures  110   1 . . . R  for a particular one of the new input pictures  104 * may be computed from that input picture as well as one or more other ones of the new input pictures  104 * (and/or other ones of the input pictures  104 ) using anyone of a number of interpolation techniques. As a result, each of the new input pictures  104 * will have associated with it a set of R corresponding interpolated pictures  110   1 . . . R . The value of R is hereinafter referred to as the “interpolation ratio” and is adjustable as will be described below. At step  208 , the image processing engine  100  blends the new input pictures  104 * together with the corresponding sets of interpolated pictures  110   1 . . . R  in accordance with a blending ratio of P N :P I . That is to say, each of the new input pictures  104 * is repeated P N  times, and then is followed by each of the R interpolated images  110   1 . . . R  being repeated P I  times. One observes that each of the new input pictures  104 * in the input picture stream  102  is responsible for the appearance of P N  copies of itself in addition to R×P I  interpolated pictures in the output picture stream  106 . Thus, the average number of new pictures  104 * (or copies thereof) appearing in the output picture stream  106  per second is NER in ×P N , while the average number of interpolated pictures or copies thereof (i.e., pictures of an interpolated nature) appearing in the output picture stream  106  per second is NFR in ×R×P I . The latter quantity can be referred to as an “average interpolated picture rate” and is denoted IFR out . This corresponds to the number of pictures of an interpolated nature that a viewer of the output picture stream  106  is exposed to. The values of P N  and P I  are adjustable as will be described below. 
         [0030]    In particular, advantage is taken of the fact that when the underlying new picture rate NFR in  is higher, human visual systems can tolerate a higher average interpolated picture rate IFR out  and likewise when the underlying new picture rate NFR in  is lower, human visual systems can tolerate a correspondingly lower average interpolated picture rate IFR out . Generally speaking, therefore, embodiments of the present invention aim to effect changes in the average interpolated picture rate IFR out  that follow changes in the underlying new picture rate NFR in . 
         [0031]    To this end, at step  205 , adjustments can be made to parameters of the interpolation (step  206 ) and blending (step  208 ) processes based on detected variations in the underlying new picture rate NFR in  (determined at step  202 ) and based on the target output frame rate FR out  (determined at step  204 ). Specifically, such adjustments or variations include:
       adjustments to R (the number of interpolated pictures  110   1 . . . R  generated for each of the new input pictures  104 *);   adjustments to P N  (the number of times each of the new input pictures  104 * is repeated in the output picture stream  106 ); and   adjustments to P 1  (the number of times each of the R interpolated images  110   1 . . . R  corresponding to a particular one of the new input pictures  104 * is repeated in the output picture stream  106 ).       
 
         [0035]    The adjustments are made so that the average interpolated picture rate IFR out  maps to an increasing function of the underlying new picture rate NFR in . That is to say, increases in the underlying new picture rate NFR in  lead to increases in the average interpolated picture rate IFR out  while decreases in the underlying new picture rate NFR in  lead to in decreases in the average interpolated picture rate IFR out . 
         [0036]    By way of specific non-limiting example, and with reference to  FIG. 3 , consider the case where during a time interval denoted A, an input picture stream  302  with a plurality of input pictures  304  has an input frame rate of FR in =60 pps and an underlying new picture rate of NFR in =60 pps; in other words, each of the ‘input pictures  304  is new. Consider that the image processing engine  100  indeed determines at step  202  that the underlying new picture rate NFR in =60 pps and, at step  204 , maps this value to a target output frame rate of FR out =120 pps. 
         [0037]    In order to achieve this value of the output frame rate FR out  from the measured underlying new picture rate NFR in , let it be assumed that execution of step  205  yields certain values of R, P N  and P I  such that at step  206 , the image processing engine  100  generates one interpolated picture  310  for each new input picture  304  (i.e., R=1), and at step  208 , the image processing engine  100  blends the new and interpolated pictures  304 ,  310  in a ratio (hereinafter referred to as a “blending ratio”) of P N :P I =1:1. This yields an output picture stream  306  comprising output pictures  308  where, out of every group of 120 output pictures  308  per second, half of them will have been of the interpolated variety, i.e., the average interpolated picture rate IFR out  is 60 pps. 
         [0038]    Consider now that during the next time interval denoted B, the underlying new picture rate changes (drops) to NFR in =24 pps. Meanwhile, the input frame rate FR in  may have stayed the same or may have varied; to a certain extent, the input frame rate FR in  is irrelevant. For illustrative purposes, take the case where the input frame rate FR in  stays the same at 60 pps, the input picture stream  302  could now consist of a first new picture  304 * 1 , a repeated version of the first new picture  3041 , a second new picture  304 * 2 , two repeated versions of the second new picture  3042 ,  3042 , a third new picture  304 * 3 , a repeated version of the third new picture  304   3 , and so on. Thus, 24 new input pictures  304  per second result in the input frame rate FR in  being equal to 12×2+12×3=60 pps. The underlying new picture rate NFR in  is again detected by the image processing engine  100  at step  202 . Then at step  204 , the image processing engine  100  maps the input frame rate NFR in =24 pps to a suitable output frame rate FR out . Suitable but non-limiting examples include FR out =48 pps, FR out =72 pps and F out =120 pps. In the latter case, there is no change in the output frame rate FR out  between time intervals A and B. Thus, the output frame rate FR out  may be varied or kept constant. 
         [0039]    At step  205 , the image processing engine  100  is now faced with the prospect of varying the parameters of the blending and interpolation processes. To this end, the image processing engine  100  may vary R, the number of interpolated images generated for each of the input images, from its previous value of 1. In addition P N  (the number of times each new input picture is repeated in the output picture stream  306 ) and P I  (the number of times each of the R interpolated pictures generated for each new input picture is repeated in the output picture stream  306 ) may be varied from their previous values of 1 and 1 (which gave a blending ratio of 1:1). As will be seen from the examples below, each possible tweaking of parameters in response to the lower value of the underlying new picture rate NFR in  (which has dropped from 60 pps to 24 pps) will cause the average interpolated picture rate IFR out  to drop from its previous value of 60 pps. 
         [0040]    To this end, reference is made to  FIGS. 4A to 4C , which illustrate three Scenarios entitled IA, IB and IC, and which are all associated with parameter adjustments that can be made when the output frame rate FR out  (obtained at step  204 ) was lowered (e.g., to either 48 pps or 72 pps, depending on the embodiment, all of which are non-limiting). Specifically:
       In Scenario IA ( FIG. 4A ), R is kept constant, as is the blending ratio P N :P I . Thus, each new input picture  304 * j  is blended with a corresponding interpolated picture  310   j .   In Scenario IB ( FIG. 4B ), R is varied (in this case, increased to a value of 2), while the blending ratio P N :P I  is kept constant. Thus, each new input picture  304 * j  is blended with two corresponding interpolated pictures  310 j A ,  310 j B .   In Scenario IC ( FIG. 4C ), R is kept constant, while the blending ratio P N :P I  is varied (in this case, changed to 1:2). Thus, each new input picture  304 *j is blended with two copies of a single corresponding interpolated picture  310   j .       
 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 Time 
                 Time 
                 Time 
               
               
                   
                   
                 Interval B 
                 Interval B 
                 Interval B 
               
               
                   
                 A 
                 (scenario IA) 
                 (scenario IB) 
                 (scenario IC) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 FR in  (* = irrelevant) 
                  60* 
                  60* 
                  60* 
                  60* 
               
               
                 NFR in   
                 60 
                 24 
                 24 
                 24 
               
               
                 FR out  (=f(NFR in )) 
                 120  
                 48 
                 72 
                 72 
               
               
                 FR out /NFR in   
                  2 
                  2 
                  3 
                  3 
               
               
                 R 
                  1 
                  1 
                  2 
                  1 
               
               
                 P N   
                  1 
                  1 
                  1 
                  1 
               
               
                 P I   
                  1 
                  1 
                  1 
                  2 
               
               
                 IFR out   
                 60 
                 24 
                 48 
                 48 
               
               
                 (=R × NFR in  × P I ) 
               
               
                   
               
             
          
         
       
     
         [0044]    Reference is now made to  FIGS. 5A and 5B , which illustrate two Scenarios entitled IIA and IIB, and which are both associated with parameter adjustments that can be made when the output frame rate FR out  (obtained at step  204 ) was kept constant (i.e., at 120 pps). Specifically:
       In Scenario IIA ( FIG. 5A ), R is kept constant, while the blending ratio P N :P I  is varied (in this case, changed to 3:2). Thus, three copies of each new input picture  304 * j  are blended with two copies of a single corresponding interpolated picture  310   J .   In scenario IIB ( FIG. 5B ), R is varied (in this case, increased to a value of 2), as is the blending ratio P N :P I  (in this case, changed to 3:1). Thus, three copies of each new input picture  304 * j  are blended with two corresponding interpolated pictures  310 j A ,  310 j B .       
 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 Time Interval B 
                 Time Interval B 
               
               
                   
                 A 
                 (scenario IA) 
                 (scenario IB) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 FR in  (* = irrelevant) 
                  60* 
                  60* 
                  60* 
               
               
                 NFR in   
                 60 
                 24 
                 24 
               
               
                 FR out  (=f(NFR in )) 
                 120  
                 120  
                 120  
               
               
                 FR out /NFR in   
                  2 
                  5 
                  5 
               
               
                 R 
                  1 
                  1 
                  2 
               
               
                 P N   
                  1 
                  3 
                  3 
               
               
                 P I   
                  1 
                  2 
                  1 
               
               
                 IFR out  (=R × NFR in  × P I ) 
                 60 
                 48 
                 48 
               
               
                   
               
             
          
         
       
     
         [0047]    It is therefore seen in all cases that as the underlying new picture rate NFR in  decreases from 60 pps to 24 pps, so too does the average interpolated picture rate IFR out  (from 60 pps to either 24 pps or 48 pps). As a result, a viewer of the output picture stream  306  is exposed to fewer pictures of an interpolated nature. Of course, when the underlying new picture rate NFR 1 , increases, it is within the scope of the present invention to similarly increase the average interpolated picture rate IFR out  thus presenting the viewer of the output picture stream with more pictures of an interpolated nature. 
         [0048]    Also, it is noted that the number of interpolated pictures actually generated per second (namely, R×NFR in ) is lower during time interval B than during time interval A, even in those scenarios where the output frame rate FR out  has been kept constant. Specifically, the number of interpolated pictures generated per second during time interval B corresponds to 24 or 48, depending on the Scenario, in comparison to 60 interpolated pictures generated during time interval A. This is to be compared with a less innovative approach where maintaining the output frame rate of FR out =120 pps with a new underlying picture rate of NFR in =24 pps during time interval B would require the generation of four (4) interpolated pictures for each new picture in the input picture stream  302 , therefore increasing the number of interpolated pictures generated per second from 60 to 96, thereby engendering a corresponding increase in the computational load associated with the interpolation operation. 
         [0049]    Those skilled in the art will also appreciate that not only can the average interpolated picture rate IFR out  be increased/decreased in accordance with increases/decreases in the underlying new picture rate NFRin, but. it can also be varied in response to other factors detectable from the input picture stream  102 . Specifically, the input picture stream  102  can be processed to determine a likelihood of perceptible interpolation-induced artifacts in the output pictures  108 , based on the current values of the interpolation ratio R and the blending ratio P N :P I . For example, the image processing engine  100  can be responsive to indicators generated by various subsystems such as those responsible for pattern detection (which can signal an anomaly with pattern detection such as detection of a repetitive pattern), motion vector estimation (which can signal a lack of reliable motion vectors), to name a few non-limiting possibilities. 
         [0050]    When the likelihood is determined to be above a certain first threshold, then it may be desirable to reduce the average interpolated picture rate IFR out  in one of the ways described above that may, but does not necessarily, involve reducing the output frame rate FR out . For example, possible adjustments involve variations in R (the number of interpolated images generated for each of the new input pictures  104 *), P N  (the number of times each of the new input pictures  104 * is repeated in the output picture stream  106 ) and P I  (the number of times each of the R interpolated images  108   1 . . . R  is repeated in the output picture stream  106 ) so that the average interpolated picture rate IFR out  is decreased. The aforementioned changes may be gradual so as to result in a gradual decrease in the average interpolated picture rate IFR out . 
         [0051]    Likewise, when the likelihood of perceptible interpolation-induced artifacts in the output pictures  108  is determined to fall back below a certain second threshold (which could be the same as, or different than, the above first threshold), then it may be desirable to increase the average interpolated picture rate IFR out  in one of the ways described above, while increasing or keeping stable the output frame rate FR out . 
         [0052]    It should be appreciated that the values of FR in , FR out , NFR in  and the like were selected for exemplary purposes and do not represent limitations of the present invention. These parameters may have any suitable values in various embodiments, depending on specific operational requirements. In particular, it should be expressly understood that the present invention is applicable to input frame rates FR in  and output frame rates F out  of 25 pps and 50 pps, as well as underlying new picture rates NFR in  of 25 pps and 50 pps, which result from the use of equipment originating from Europe and certain other regions of the world. 
         [0053]    Those skilled in the art will appreciate that in some embodiments, the functionality of the image processing engine  100  may be implemented using pre-programmed hardware or firmware elements (e.g., application specific integrated circuits (ASICs), electrically erasable programmable read-only memories (EEPROMs), etc.), or other related components. In other embodiments, the functionality of the image processing engine  100  may be achieved using a computing apparatus that has access to a code memory (not shown) which stores computer-readable program code for operation of the computing apparatus, in which case the computer-readable program code could be stored on a medium which is fixed, tangible and readable directly by the image processing engine  100 , (e.g., removable diskette, CD-ROM, ROM, fixed disk, USB drive), or the computer-readable program code could be stored remotely but transmittable to the image processing engine  100  via a modem or other interface device (e.g., a communications adapter) connected to a network (including, without limitation, the Internet) over a transmission medium, which may be either a non-wireless medium (e.g., optical or analog communications lines) or a wireless medium (e.g., microwave, infrared or other transmission schemes) or a combination thereof. 
         [0054]    While specific embodiments of the present invention have been described and illustrated, it will be apparent to those skilled in the art that numerous modifications and variations can be made without departing from the scope of the invention as defined in the appended claims.