Abstract:
A method and apparatus for enhancing the performance in displaying a large bitmap image transferred from a producer device to a consumer device. When using EIA775A to transfer large bitmap images from a producer device to a consumer device performance can suffer. This is especially the case for very large images such as program guides and graphical user interfaces. Performance can be enhanced by determining if the bitmap image is larger than a predetermined threshold. If so, an audio/video control message can be sent from the producer device to the consumer device to switch from a digital connection to an analog connection. The large bitmap image can then be transferred as an analog signal rather than digital to enhance performance.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to the field of transfer of video images between video components. More particularly, the present invention relates to a method and apparatus for transferring large bitmap images between video devices by using an analog signal path rather than digital.  
         BACKGROUND OF THE INVENTION  
         [0002]    EIA775A is a protocol that defines the parameters for transferring data from a so-called “producer” device to a so-called “consumer” device. An example of a producer device might be a television set-top box or personal video recorder (PVR). An example of a consumer device might be a digital television set. This protocol is essentially overlaid on an IEEE 1394 communication bus to permit the producer device to send information to the consumer device. EIA775A protocol provides a method to transmit OSD (On Screen Data) information via an “asynchronous push” connection on an IEEE 1394 link.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention relates generally to communication between a producer device and a consumer device. Objects, advantages and features of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the invention.  
           [0004]    In one embodiment consistent with certain embodiments of the present invention a method and apparatus is provided for enhancing the performance in displaying a large bitmap image transferred from a producer device to a consumer device. When using EIA775A to transfer large bitmap images from a producer device to a consumer device, performance can suffer. This is especially the case for very large images such as program guides and graphical user interfaces. Performance can be enhanced by determining if the bitmap image is larger than a predetermined threshold. If so, an audio/video control message can be sent from the producer device to the consumer device to switch from a digital connection to an analog connection. The large bitmap image can then be transferred as an analog signal rather than digital to advantageously enhance performance.  
           [0005]    A method, consistent with certain embodiments of the present invention, of transmitting images from a producer device to a consumer device, comprises at the producer device: determining that a digital bitmap image is larger in size than a threshold; converting the digital bitmap image to an analog image; and sending the analog image to the consumer device.  
           [0006]    Another method, consistent with certain embodiments of the present invention, of transmitting images from a producer device to a consumer device, comprises at the producer device: determining if a digital bitmap image is larger in size than a threshold and if the digital bitmap image is larger is size than the threshold: converting the digital bitmap image to an analog image; sending a control message as an audio video control (AVC) command to the consumer device to switch from a digital input to an analog input to receive the analog image; sending the analog image to the consumer device; and if the digital bitmap image is not larger is size than the threshold: sending the digital images using EIA775a protocol over an IEEE 1394 isochronous digital connection.  
           [0007]    Another method, consistent with certain embodiments of the present invention, of transmitting images from a television set-top box to a digital television, comprises at the television set-top box: determining if a digital bitmap image is larger in size than a threshold and if the digital bitmap image is larger is size than the threshold: converting the digital bitmap image to an analog image; sending a control message as an audio video control (AVC) command to the digital television to switch from a digital input to an analog input to receive the analog image; sending the analog image to the digital television; and if the digital bitmap image is not larger is size than the threshold: sending the digital images using EIA775a protocol over an IEEE  1394  digital connection.  
           [0008]    A producer device consistent with certain embodiments of the present invention has a circuit that receives digital content containing a bitmap image. A processor determines a size of the bitmap image. The bitmap image is converted to an analog representation in the event the size of the bitmap image exceeds a threshold. A digital output circuit sends digital information to a consumer device. An analog output circuit sends the analog representation to the consumer device.  
           [0009]    The above summaries are intended to illustrate exemplary embodiments of the invention, which will be best understood in conjunction with the detailed description to follow, and are not intended to limit the scope of the appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself however, both as to organization and method of operation, together with objects and advantages thereof, may be best understood by reference to the following detailed description of the invention, which describes certain exemplary embodiments of the invention, taken in conjunction with the accompanying drawings in which:  
         [0011]    [0011]FIG. 1 is a conceptual block diagram of a producer device and a consumer device consistent with certain embodiments of the present invention.  
         [0012]    [0012]FIG. 2 is a flow chart depicting a process for switching between digital and analog signal paths for efficiently handling large bitmap data consistent with certain embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail specific embodiments, with the understanding that the present disclosure is to be considered as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described. In the description below, like reference numerals are used to describe the same, similar or corresponding parts in the several views of the drawings.  
         [0014]    Whenever large amounts of data are transmitted using EIA775A, performance can be poor. This is due in part to the large amount of data associated with an uncompressed bitmap image, but it is also related to the EIA775A protocol&#39;s overhead requirements along with the overhead requirements of IEEE 1394 communications, along with the speed limitation of IEEE 1394. The present invention seeks to improve performance in a large bitmap image scenario by utilizing an analog signal path to transmit analog images rather than digital bitmap images when the bitmap image size exceeds a threshold. An appropriate threshold, can be readily determined experimentally, for example, to be a bitmap size that results in noticeable delays in display of the digital image. However, this is not to be considered limiting since other systems may deviate from this particular threshold without departing from the present invention.  
         [0015]    An example of the type of scenario wherein transfer of large bitmap images can produce poor performance is in the case where on-screen data (OSD) representing a program guide is being delivered from a television set-top box to a digital television. In this situation, the OSD can represent a large bitmap image which transfers very slowly between the set-top box and the digital television, and thus creates a scenario wherein the user must endure delays awaiting completion of the data transfer.  
         [0016]    [0016]FIG. 1 depicts broadly a producer device  10  communicating via both digital and analog signal paths with a consumer device  14 . As previously described, producer device  10  may represent, for example, a television set-top box while consumer device  14  may represent, for example, a digital television. For purposes of this example, it is assumed that producer device  10  receives or contains content which is in digital form illustrated by digital content  18 . This content is analyzed by a control processor  22  which makes a determination as to whether or not a large bitmap image is to be transmitted over a digital interface  26 . If a large bitmap image is to be transmitted, the control processor switches, using switch  30 , the digital content from  18  through a digital-to-analog converter  34  and transmits analog content over an analog interface  38  (of course, the analog content is overlaid on a conventional analog television protocol such as, for example, PAL or NTSC). In addition, control processor  22  sends a message over digital connection  26  to the consumer device  14  to instruct the consumer device to switch to an analog input for receipt of the signal.  
         [0017]    At consumer device  14 , the digital connection  26  passes data to a digital interface  42  and then on to switch  58 , where switch  58  is operated under control of a control processor  46 , before passing the digital signal to television signal processing circuitry  50  for display on a television display (assuming that the consumer device  14  is a digital television.) Similarly, analog signals through analog connection  38  pass through an analog interface  54  and then on through switch  58  to the television signal processing circuitry. Depending upon the position of switch  58 , which is operated under control of control processor  46  based upon signals received via the digital interface  42  and passed on to control processor  46 , either the digital image from digital connection  26  and digital interface  42  passes to the television signal processing circuitry  50  or the analog signal from analog interface  54  passes through switch  58  to television signal processing circuitry  50 . Switch  58  operates under the control of control processor  46  based upon messages received from producer device  10  instructing the control processor to accept input as either analog or digital.  
         [0018]    Of course, those skilled in the art will recognize that the present invention as depicted in FIG. 1 is illustrative of the concept used to transmit large bitmap images as analog signals and is not necessarily directly correlated with hardware or software present within the consumer or producer devices. Those skilled in the art will understand how to adapt the various designs of producer devices to effect the operation described herein.  
         [0019]    [0019]FIG. 2 depicts a process  100  starting at  102  for implementing an embodiment of the present invention, for example, in software within a microprocessor or micro-controller device. At  106 , digital content is retrieved or received from a source of such content (e.g., a cable system, a satellite system, or a storage device such as a disk drive or memory). The content is analyzed at  110  to determine if an OSD bitmap image is to be displayed which exceeds a threshold in size. If not, the OSD data is transmitted to the DTV over the IEEE1394 bus ussing the EIA 775a protocol and are mixed with the decoded MPEG viedo in the DTV prior to being presented to the display. Control then returns to  106  to retrieve or receive the next segment of digital content.  
         [0020]    If, on the other hand, the OSD bitmap data exceeds the predetermined threshold at  110 , control passes to  118  where an audio/video control (AVC) command is sent from the producer device to the consumer device instructing the consumer device to switch from its digital input to its analog input. The bitmap image is then converted to analog at  122  and the analog OSD image is overlaid with the analog signal stream and sent to the consumer device over the analog connection at  126 . Once the image has been completely transmitted and there is no further large bitmap data to be transmitted as analog at  130 , an audio video control command is sent at  134  to the consumer device instructing the consumer device to switch back to the digital input and control returns to  106 .  
         [0021]    In this manner large bitmap images which would normally degrade system performance can be efficiently transmitted as analog and substantially enhance performance. The above technique is particularly useful to display information such as graphical user interface information, program guides and the like using NTSC or PAL analog video for delivery and display via an analog communication path on digital television.  
         [0022]    Those skilled in the art will recognize that the present invention has been described in terms of exemplary embodiments based upon use of a programmed processor such as control processors  22  and  46 . However, the invention should not be so limited, since the present invention could be implemented using hardware component equivalents such as special purpose hardware and/or dedicated processors which are equivalents to the invention as described and claimed. Similarly, general purpose computers, microprocessor based computers, micro-controllers, optical computers, analog computers, dedicated processors and/or dedicated hard wired logic may be used to construct alternative equivalent embodiments of the present invention.  
         [0023]    Those skilled in the art will appreciate that the program steps and associated data used to implement the embodiments described above can be implemented using disc storage as well as other forms of storage such as for example Read Only Memory (ROM) devices, Random Access Memory (RAM) devices; optical storage elements, magnetic storage elements, magneto-optical storage elements, flash memory, core memory and/or other equivalent storage technologies without departing from the present invention. Such alternative storage devices should be considered equivalents.  
         [0024]    The present invention, as described in embodiments herein, is implemented using a programmed processor executing programming instructions that are broadly described above in flow chart form that can be stored on any suitable electronic storage medium or transmitted over any suitable electronic communication medium. However, those skilled in the art will appreciate that the processes described above can be implemented in any number of variations and in many suitable programming languages without departing from the present invention. For example, the order of certain operations carried out can often be varied, additional operations can be added or operations can be deleted without departing from the invention. Error trapping can be added and/or enhanced and variations can be made in user interface and information presentation without departing from the present invention. Such variations are contemplated and considered equivalent.  
         [0025]    While the invention has been described in conjunction with specific embodiments, it is evident that many alternatives, modifications, permutations and variations will become apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended that the present invention embrace all such alternatives, modifications and variations as fall within the scope of the appended claims.