Patent Abstract:
An apparatus generally including an internal memory and a direct memory access controller is disclosed. The direct memory access controller may be configured to (i) read first information from an external memory across an external bus, (ii) generate second information by processing the first information, (iii) write the first information across an internal bus to a first location in the internal memory during a direct memory access transfer and (iv) write the second information across the internal bus to a second location in the internal memory during the direct memory access transfer. The second location may be different from the first location.

Full Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to direct memory access control generally and, more particularly, to a method and/or apparatus for implementing a multi-destination direct memory access transfer. 
       BACKGROUND OF THE INVENTION 
       [0002]    Video processing, video coding, and graphics application technologies are markets that have been growing substantially over the last few years. The technologies are combined into many applications and are widely used. Video data bandwidth usage is high especially since video resolution enabled on televisions and personal computer monitors keep increasing all the time. For example, 1080 progressive (1080P) resolution is available now in most new televisions. An associated bandwidth for a simple display of 1080P video is about 3 gigabits per second. Digital signal processors performing video coding, video processing or graphics applications are sensitive to memory bandwidth criteria. The memory bandwidth criteria limit the performance of many systems rather than processing power. Therefore, memory bandwidth optimization is useful in order to enable such applications. 
         [0003]    Many video processing techniques utilize several copies of a frame at several locations within a memory. Three-dimensional (3D) graphics applications also perform texture mapping over 3D scenes by considering the resolution from which to extract the current level of detail specified after a 3D warping. Furthermore, scalable Video Coding (SVC) uses multi-resolution representations of the video. The multi-resolution representations enable both error resilient transmission of the video and an ability to personalize video experience according to the edge device capabilities and type of service (i.e., standard or prime services). 
         [0004]    Referring to  FIG. 1 , a block diagram of a conventional method  10  for creating multi-destination copies is shown. In the method  10 , a frame stored at a location  12  is read directly from a memory  14  to two or more locations  16   a - 16   b  in another memory  18  using two independent transfers  20   a - 20   b . The transfers  20   a - 20   b  are controlled by a direct memory access engine  22 . A problem with the method  10  is that a bandwidth cost for the memory  14  is high, the total transfer is typically slow and a bottleneck is created for the application relying on the frames in the memory  18 . In the method  10 , the bandwidth involved is two frame reads from the memory  14  and two frames writes into the memory  18 . 
         [0005]    Referring to  FIG. 2 , a block diagram of another conventional method  30  for creating multi-destination copies is shown. In the method  30 , the frame at the location  12  is read from the memory  14  to the location  16   a  using the transfer  20   a . The direct memory access engine  22  then copies the frame from the location  16   a  to the location  16   b  in another transfer  32 . The lack of the transfer  20   b  decreases the bandwidth consumption of the memory  14  compared with the method  10 . However, method  30  still causes some issues. In particular, congestion is created in the memory  18 , especially if both copies of the frame in the memory  18  are to be accessed temporally proximate each other. A synchronization issue is also created due to the transfer  20   a  writing to the location  16   a  while the transfer  32  tries to read from the location  16   a . Furthermore, the internal memory bandwidth of the memory  18  is increased due to the added read from the location  16   a  at the start of the transfer  32 . 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention concerns an apparatus generally including an internal memory and a direct memory access controller. The direct memory access controller may be configured to (i) read first information from an external memory across an external bus, (ii) generate second information by processing the first information, (iii) write the first information across an internal bus to a first location in the internal memory during a direct memory access transfer and (iv) write the second information across the internal bus to a second location in the internal memory during the direct memory access transfer. The second location may be different from the first location. 
         [0007]    The objects, features and advantages of the present invention include providing a method and/or apparatus for implementing a multi-destination direct memory access transfer that may (i) read data from a source and store the data in several destinations, (ii) decimate the data before storing in one or more of the destinations, (iii) interpolate the data before storing in one or more of the destinations, (iv) filter the data before storing in one or more of the destinations, (v) reduce a bandwidth utilization of the source, (vi) maintain bandwidth utilization of the destinations, (vii) avoid congestion at the destinations, and/or (viii) free digital signal processing power from the task of making multiple copies of the data. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    These and other objects, features and advantages of the present invention will be apparent from the following detailed description and the appended claims and drawings in which: 
           [0009]      FIG. 1  is a block diagram of a conventional method for creating multi-destination copies; 
           [0010]      FIG. 2  is a block diagram of another conventional method for creating multi-destination copies; 
           [0011]      FIG. 3  is a block diagram of an apparatus in accordance with a preferred embodiment of the present invention; 
           [0012]      FIG. 4  is a functional flow diagram of an example method for a multi-destination transfer; 
           [0013]      FIG. 5  is a functional block diagram of an example method for a processed, multi-destination transfer; and 
           [0014]      FIG. 6  is a functional flow diagram of another example method for a multi-destination transfer. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    Referring to  FIG. 3 , a block diagram of an apparatus  100  is shown in accordance with a preferred embodiment of the present invention. The apparatus (or device or circuit)  100  generally comprises a circuit (or module)  102 , a circuit (or module)  104 , a circuit (or module)  106 , a circuit (or module)  107 , a circuit (or bus)  108  and a circuit (or bus)  110 . The circuits  102  to  110  may represent modules and/or blocks that may be implemented as hardware, firmware, software, a combination of hardware, firmware and/or software, or other implementations. 
         [0016]    A signal (e.g., EXT) may be conveyed by the bus  108  between the circuit  102  and the circuit  104 . In some embodiments, the signal EXT may be a bidirectional signal. A signal (e.g., INT) may be conveyed by the bus  110  between the circuit  104 , the circuit  106  and the circuit  107 . In some embodiments, the signal INT may be a bidirectional signal. A signal (e.g., TASK) may be presented from the circuit  107  to the circuit  104 . 
         [0017]    The circuit  102  may be fabricated in (on) a die (or chip)  112 . In some embodiments, the circuits  104 ,  106 ,  107  and  110  may be fabricated in (on) another die (or chip)  114 . In other embodiments, all of the circuits  102 - 110  may be fabricated in (on) the same die (e.g.,  112  or  114 ). 
         [0018]    The circuit  102  may implement an external memory circuit. The circuit  102  is generally operational to store data presented to and received from the circuit  104  via the signal EXT on the bus  108 . In some embodiments, the circuit  102  may be implemented as a double data rate (DDR) memory. Other memory technologies may be implemented to meet the criteria of a particular application. Since the circuit  102  may be fabricated on the die  112  apart from the die  114 , the circuit  102  may be considered external to the circuits of the die  114 . 
         [0019]    The circuit  104  may be implemented as a Direct Memory Access (DMA) controller circuit. The circuit  104  may be operational to transfer the data between the circuit  102  and the circuit  106  in one or more DMA transfer operations. Some transfers may be from a single location in a source circuit (e.g.,  102 ) to a single location in a destination circuit (e.g.,  106 ). Other transfers may be from a single location in the source circuit to two or more locations in the destination circuit. 
         [0020]    Where a DMA transfer involves multiple destinations, the circuit  104  may be further operational to process the data routed to at least one of the locations in the destination circuit. Processing may include, but is not limited to, decimation, interpolation, filtering and/or deinterlacing of the data. For example, where the data is an image, picture, frame or field from a video sequence or still picture, the decimation may include removal of every other pixel horizontally and/or vertically. Other decimation techniques may be implemented to meet the criteria of a particular application. As a result, an image may be copied from the circuit  102  to a given location in the circuit  106  at full resolution while another smaller version of the image may be written to another location in the circuit  106 . 
         [0021]    Where the processing is an interpolation, multiple copies of an image may be copied from the circuit  102  to multiple locations in the circuit  106 . Each copy in the circuit  106  may have a different size (or resolution). For example, a standard video frame (e.g., 720 by 480 pixels) may be copied from the circuit  102  to a particular location in the circuit  106  without interpolation. Another copy of the standard video frame may be interpolated to a high resolution (e.g., 1920 by 1080 pixels) and stored at a different location in the circuit  106 . Furthermore, the processing may include conversion of the interlaced fields into progressive frames. Therefore, the circuit  106  may contain both standard and high-definition frames that are eventually presented to a standard and/or high-definition displays and/or recording devices. 
         [0022]    Where the process is filtering, a lowpass filter may be implemented to smooth the data (e.g., smooth an image of a still picture or field/frame of video. The lowpass filtering may also be designed to decimate pictures/fields/frames. High-pass filtering may also be implemented to sharpen details in the pictures/fields/frames. Other types of filtering may be implemented to meet the criteria of a particular application. 
         [0023]    The circuit  106  may implement one or more internal memory circuits. The circuit  106  is generally operational to store one or more copies of the data received from and/or present data to the circuit  104  in the signal INT. In some embodiments, the circuit  106  my implement a static random access memory. In other embodiments, the circuit  106  may implement a dynamic random access memory. Other memory technologies may be implemented to meet the criteria of a particular application. Since the circuit  106  may be fabricated on the same die  114  as the circuit  104 , the circuit  106  may be considered an internal memory. 
         [0024]    The circuit  107  may implement a Digital Signal Processor (DSP) circuit. The circuit  107  is generally operational to process the data stored in the circuit  106 . The processing may include, but is not limited to video processing, graphics processing, audio processing and still picture processing. Access to the circuit  106  may be via bus  110 . The circuit  107  may also be operational to configure the circuit  104  to perform one or more DMA transfer operations. Configuring may be achieved by loading a source address and one or more destination addresses into the circuit  104  via the signal TASK. 
         [0025]    The circuit  108  may implement an external memory bus circuit. The circuit  108  is generally operational to achieve control of the circuit  102  and transfer data to and from the circuit  102 . Where the circuit  102  is fabricated on a die separate from the circuit  104 , line drivers, electrostatic discharge circuitry, termination circuitry and the like may be implemented for the circuit  108 . In some embodiments, the circuit  108  is a point-to-point bus to connect to a single circuit  102 . In other embodiments, the circuit  108  may implement a multi-drop bus to connect to multiple circuits  102 . Other inter-chip bus technologies may be implemented to meet the criteria of a particular application. 
         [0026]    The circuit  110  may implement an internal memory bus circuit. The circuit  110  is generally operational to exchange data between the circuit  104  and the circuit  106  and between the circuit  106  and the circuit  107 . In some embodiments, the circuit  110  may be a multi-drop bus. Other intra-chip bus technologies may be implemented to meet the criteria of a particular application. 
         [0027]    Referring to  FIG. 4 , a functional flow diagram of an example method  120  for a multi-destination transfer is shown. The method (or process)  120  generally comprises a step (or operation)  122 , a step (or operation)  124 , a step (or operation)  126 , a step (or operation)  128 , a step (or operation)  130  and a step (or operation)  132 . The steps  122  to  132  may represent modules and/or blocks that may be implemented as hardware, firmware, software, a combination of hardware, firmware and/or software, or other implementations. The method  120  may be performed by the apparatus  100 . 
         [0028]    In the step  122 , data (e.g., a frame) may be stored in the circuit  102 . The data may be transferred (e.g., read) from the circuit  102  to the circuit  104  in the step  124 . The transfer may take place on the bus  108 . Step  124  may form a part of a single DMA transfer operation. In the step  126 , the circuit  104  may transfer (e.g., write) the data to the circuit  106  via the bus  110 . The circuit  106  may store the data in the step  128  at a given location. The transfer of step  126  and storage of step  128  may also form parts of the single DMA transfer operation. The data may undergo another transfer (e.g., write) from the circuit  104  to the circuit  106  in the step  130 . The transfer of step  130  may also take place on the bus  110 . In the step  132 , the data may be stored in the circuit  106  at another location. The transfer of step  130  and the storage of step  132  may form parts of the single DMA transfer. Steps  130  and  132  may be performed in parallel to steps  126  and  128 . Although the method  120  illustrates two destinations for the data in the circuit  106 , other embodiments may write the data to three or more destinations using the same technique. 
         [0029]    Referring to  FIG. 5 , a functional block diagram of an example method  140  for a processed, multi-destination transfer is shown. The method (or process)  140  generally comprises the step  122 , the step  124 , the step  126 , the step  128 , a step (or operation)  142 , a step (or operation)  144  and a step (or operation)  146 . The steps  122  to  146  may represent modules and/or blocks that may be implemented as hardware, firmware, software, a combination of hardware, firmware and/or software, or other implementations. The method  140  may be performed by the apparatus  100 . 
         [0030]    The steps  122  to  128  in the method  140  may be the same as in the method  120 . In the step  122 , data (e.g., a frame) may be stored in the circuit  102 . The data may be transferred (e.g., read) from the circuit  102  to the circuit  104  in the step  124 . The transfer may take place on the bus  108 . Step  124  may form a part of a single DMA transfer operation. In the step  126 , the circuit  104  may transfer (e.g., write) the data to the circuit  106  via the bus  110 . The circuit  106  may store the data in the step  128  at a given location. The transfer of step  126  and storage of step  128  may also form parts of the single DMA transfer operation. 
         [0031]    In the step  142 , the circuit  104  may process the data as received from the circuit  102 . The processing may include, but is not limited to, decimating, interpolating, filtering and/or deinterlacing. Step  142  may be performed in parallel to steps  126  and  128 . In the step  144 , the processed data may be transferred from the circuit  104  to the circuit  106  via the bus  110 . The circuit  106  may store the processed data in the step  146  at another location, different from the location used in the step  128 . Although the method  140  illustrates two destinations for the data in the circuit  106 , other embodiments may write the data to three or more destinations using the same technique. 
         [0032]    As illustrated in the methods  120  and  140 , the circuit  100  generally has a capability to receive and operate on a source location and several destination locations. Writing to the several destination locations may be performed using one or more transfer techniques, depending on the capabilities of the circuit  106 . The transfer techniques may include, but are not limited to, sequential, parallel, interleaved and/or alternating transfers. For example, where the circuit  106  has a single data port, the circuit  104  may perform multiple sequential transfers through the data port to write the data to multiple locations (or addresses). Where the circuit  106  is implemented as a multiport device, the circuit  104  may transfer multi-destination data in parallel to respective multiple ports. The data may be multiple copies of the same data or a copy of the data and a copy of processed data. In either situation, a frame or other block of data may be read once from a single location in the circuit  102  and written into the circuit  106  at multiple locations. Thus, the bandwidth utilized on the bus  108  and the circuit  102  may be a single read operation. The bandwidth utilized on the bus  110  and the circuit  106  may be N writes, where N is the number of copies written into the circuit  106 . 
         [0033]    Furthermore, the apparatus  100  generally avoids the congestion issue and the synchronization issue described for  FIG. 2 . In particular, the writes (e.g., step  128  and  132 ) of the data into multiple different areas of the circuit  106  may be performed independently of each other. Furthermore, the write of step  128  into an area of the circuit  106  does not have to be synchronized with a subsequent read from the same area. 
         [0034]    Improvements in performance may be created by the processing step  142  of the method  140 . By processing the data before writing to the circuit  106 , the method  140  generally avoids a subsequent read and a subsequent write to the circuit  106 . For example, without the step  142 , data written unprocessed to an area of the circuit  106  may be subsequently read from the circuit  106 , processed elsewhere (e.g., the circuit  107 ) and then written back into the circuit  106 . Processing elsewhere uses additional bandwidth necessitated by the pre-processing read from the circuit  106  and the post-processing write to the circuit  106 . Buffering the unprocessed data in the circuit  106  may also increase the utilized storage capacity of the circuit  106 . For example, where the processing is a decimation of the frame, two full frames may be initially stored in the circuit  106 . After decimation of a frame copy by half both vertically and horizontally, a quarter-sized frame may be written back into the circuit  106 . Therefore, the circuit  106  should be sized to handle the two full frames plus the quarter-size frame. Using the method  140 , the data is processed (e.g., decimated) before the initial write into the circuit  106 . Therefore, the circuit  106  may be sized to store a full frame and the smaller quarter-sized frame, a savings of three-quarters of a frame. Method  140  may also save processing power of the circuit  107 . By performing the initial processing in the circuit  106 , the processed data may be readily available to the circuit  107  in a more suitable form. 
         [0035]    Referring to  FIG. 6 , a functional flow diagram of an example method  160  for a multi-destination transfer is shown. The method (or process)  160  generally comprises a step (or operation)  162 , a step (or operation)  164 , a step (or operation)  166 , a step (or operation)  168 , a step (or operation)  170 , a step (or operation)  172  and a step (or operation)  174 . The steps  162  to  174  may represent modules and/or blocks that may be implemented as hardware, firmware, software, a combination of hardware, firmware and/or software, or other implementations. The method  160  may be performed by the apparatus  100 . 
         [0036]    In the step  162 , data may be stored in the circuit  106 . The data may be transferred (e.g., read) from the circuit  106  to the circuit  104  in the step  164 . The transfer may take place on the bus  110 . Step  164  may form a part of a single DMA transfer operation. In the step  166 , the circuit  104  may transfer (e.g., write) the data to the circuit  102  via the bus  108 . The circuit  102  may store the data in the step  168  at a given location. The transfer of step  166  and storage of step  168  may also form parts of the single DMA transfer operation. Within the circuit  104 , the data may undergo optional processing in the step  170 . The processed data may be transferred (e.g., write) from the circuit  104  to the circuit  102  in the step  172 . The transfer of step  172  may also take place on the bus  108 . In the step  174 , the data may be stored in the circuit  102  at another location. The transfer of step  172  and the storage of step  174  may form parts of the single DMA transfer. Although the method  160  illustrates two destinations for the data in the circuit  102 , other embodiments may write the data to three or more destinations using the same technique. 
         [0037]    The architecture of the apparatus  100  generally improves memory bandwidth utilization problems commonly found in video processing, 3D graphics and other high memory bandwidth applications. The methods  120 ,  140  and/or  160  generally result in better bandwidth utilization of the circuit  102 , the circuit  106 , the bus  108  and the bus  110  than existing methods. The methods  120 ,  140  and/or  160  generally do not suffer from the congestion problem and synchronization problem associated with the method  30 . Establishing multiple resolution versions of a frame in the circuit  106  as part of a single DMA transfer operation has an advantage. For example, the creation of downscaled versions of the frame saves the circuit  107  from reading from the circuit  106 , performing the downscaling operation and writing back to the circuit  106 . 
         [0038]    The methods  120 ,  140  and/or  160  generally enable efficient memory copying operations for video, graphics and other applications, in which the same content is copied from the source circuit to multiple locations in the destination circuit and/or at multiple resolutions. The multi-resolution and/or multi-location copy operations may be performed by a circuit  104  having a design optimized for the particular application(s). 
         [0039]    The apparatus  100  generally reads data from a source and stores the data into several destinations. Decimation, interpolation, filtering, deinterlacing and/or other processing techniques may be applied to one or more of the copies during the DMA transfer operation. Therefore, the apparatus  100  generally lowers the bandwidth utilization of both the circuits  102  and  106 , does not suffer from the congestion problems or the synchronization problems. The apparatus  100  may also free the circuit  107  to perform other useful tasks by performing initial processing of one or more of the copies. 
         [0040]    The functions performed by the diagrams of  FIGS. 4-6  may be implemented using one or more of a conventional general purpose processor, digital computer, microprocessor, microcontroller, RISC (reduced instruction set computer) processor, CISC (complex instruction set computer) processor, SIMD (single instruction multiple data) processor, signal processor, central processing unit (CPU), arithmetic logic unit (ALU), video digital signal processor (VDSP) and/or similar computational machines, programmed according to the teachings of the present specification, as will be apparent to those skilled in the relevant art(s). Appropriate software, firmware, coding, routines, instructions, opcodes, microcode, and/or program modules may readily be prepared by skilled programmers based on the teachings of the present disclosure, as will also be apparent to those skilled in the relevant art(s). The software is generally executed from a medium or several media by one or more of the processors of the machine implementation. 
         [0041]    The present invention may also be implemented by the preparation of ASICs (application specific integrated circuits), Platform ASICs, FPGAs (field programmable gate arrays), PLDs (programmable logic devices), CPLDs (complex programmable logic device), sea-of-gates, RFICs (radio frequency integrated circuits), ASSPs (application specific standard products), one or more monolithic integrated circuits, one or more chips or die arranged as flip-chip modules and/or multi-chip modules or by interconnecting an appropriate network of conventional component circuits, as is described herein, modifications of which will be readily apparent to those skilled in the art(s). 
         [0042]    The present invention thus may also include a computer product which may be a storage medium or media and/or a transmission medium or media including instructions which may be used to program a machine to perform one or more processes or methods in accordance with the present invention. Execution of instructions contained in the computer product by the machine, along with operations of surrounding circuitry, may transform input data into one or more files on the storage medium and/or one or more output signals representative of a physical object or substance, such as an audio and/or visual depiction. The storage medium may include, but is not limited to, any type of disk including floppy disk, hard drive, magnetic disk, optical disk, CD-ROM, DVD and magneto-optical disks and circuits such as ROMs (read-only memories), RAMS (random access memories), EPROMs (electronically programmable ROMs), EEPROMs (electronically erasable ROMs), UVPROM (ultra-violet erasable ROMs), Flash memory, magnetic cards, optical cards, and/or any type of media suitable for storing electronic instructions. 
         [0043]    The elements of the invention may form part or all of one or more devices, units, components, systems, machines and/or apparatuses. The devices may include, but are not limited to, servers, workstations, storage array controllers, storage systems, personal computers, laptop computers, notebook computers, palm computers, personal digital assistants, portable electronic devices, battery powered devices, set-top boxes, encoders, decoders, transcoders, compressors, decompressors, pre-processors, post-processors, transmitters, receivers, transceivers, cipher circuits, cellular telephones, digital cameras, positioning and/or navigation systems, medical equipment, heads-up displays, wireless devices, audio recording, storage and/or playback devices, video recording, storage and/or playback devices, game platforms, peripherals and/or multi-chip modules. Those skilled in the relevant art(s) would understand that the elements of the invention may be implemented in other types of devices to meet the criteria of a particular application. 
         [0044]    As would be apparent to those skilled in the relevant art(s), the signals illustrated in  FIGS. 3-6  represent logical data flows. The logical data flows are generally representative of physical data transferred between the respective blocks by, for example, address, data, and control signals and/or busses. The system represented by the circuit  100  may be implemented in hardware, software or a combination of hardware and software according to the teachings of the present disclosure, as would be apparent to those skilled in the relevant art(s). 
         [0045]    While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the scope of the invention.

Technology Classification (CPC): 8