Intelligent MSI-X interrupts for video analytics and encoding

Video analytics may be used to assist video encoding by selectively encoding only portions of a frame and using, instead, previously encoded portions. Previously encoded portions may be used when succeeding frames have a level of motion less than a threshold. In such case, all or part of succeeding frames may not be encoded, increasing bandwidth and speed in some embodiments.

BACKGROUND

This relates generally to computers and, particularly, to video processing.

There are a number of applications in which video must be processed and/or stored. One example is video surveillance, wherein one or more video feeds may be received, analyzed, and processed for security or other purposes. Another conventional application is for video conferencing.

Typically, general purpose processors, such as central processing units, are used for video processing. In some cases, a specialty processor, called a graphics processor, may assist the central processing unit.

Video analytics involves obtaining information about the content of video information. For example, the video processing may include content analysis, wherein the content video is analyzed in order to detect certain events or occurrences or to find information of interest.

Message signaled interrupts or MSI is a technique for generating an interrupt. Typically, each device has an interrupt pin asserted when the device wants to interrupt a host central processing unit. In the Peripheral Component Interconnect Express specification, there are no separate interrupt pins. Instead special messages allow emulation of a pin assertion or de-assertion. Message signaled interrupts allow the device to write a small amount of data to a special address in memory space. The chipset then delivers an interrupt to the central processing unit.

MSI-X permits a device to allocate up to two thousand forty eight interrupts. MSI-X is specified in the Peripheral Component Interconnect Express Base specifications, revisions 1.0a and 1.1 in section 6.1. MSI-X allows a large number of interrupts, giving each interrupt a separate target address and an identifying data word. It uses 64-bit addressing and interrupt masking.

DETAILED DESCRIPTION

In accordance with some embodiments, multiple streams of video may be processed in parallel. The streams of video may be encoded at the same time video analytics are being implemented. Moreover, each of a plurality of streams may be encoded, in one shot, at the same time each of a plurality of streams are being subjected to video analytics. In some embodiments, the characteristics of the encoding or the analytics may be changed by the user on the fly while encoding or analytics are already being implemented.

While an example of an embodiment is given in which video analytics are used, in some embodiments, video analytics are only optional and may or may not be used.

Referring toFIG. 1, a computer system10may be any of a variety of computer systems, including those that use video analytics, such as video surveillance and video conferencing application, as well as embodiments which do not use video analytics. The system10may be a desk top computer, a server, a laptop computer, a mobile Internet device, or a cellular telephone, to mention a few examples.

The system10may have one or more host central processing units12, coupled to a system bus14. A system memory22may be coupled to the system bus14. While an example of a host system architecture is provided, the present invention is in no way limited to any particular system architecture.

The system bus14may be coupled to a bus interface16, in turn, coupled to a conventional bus18. In one embodiment, the Peripheral Component Interconnect Express (PCIe) bus may be used, but the present invention is in no way limited to any particular bus.

A video analytics engine20may be coupled to the host via a bus18. In one embodiment, the video analytics engine may be a single integrated circuit which provides both encoding and video analytics. In one embodiment, the integrated circuit may use embedded Dynamic Random Access Memory (EDRAM) technology. However, in some embodiments, either encoding or video analytics may be dispensed with. In addition, in some embodiments, the video analytics engine20may include a memory controller that controls an on-board integrated two dimensional matrix memory, as well as providing communications with an external memory.

Thus, in the embodiment illustrated inFIG. 1, the video analytics engine20communicates with a local dynamic random access memory (DRAM)19. Specifically, the video analytics engine20may include a memory controller50for accessing the memory19. Alternatively, the video analytics engine20may use the system memory22and may include a direct connection to system memory.

Also coupled to the video analytics engine20may be one or more cameras24. In some embodiments, up to four simultaneous video inputs may be received in standard definition format. In some embodiments, one high definition input may be provided on three inputs and one standard definition may be provided on the fourth input. In other embodiments, more or less high definition inputs may be provided and more or less standard definition inputs may be provided. As one example, each of three inputs may receive ten bits of high definition input data, such as R, G and B inputs or Y, U and V inputs, each on a separate ten bit input line.

One embodiment of the video analytics engine20, shown inFIG. 2, is depicted in an embodiment with four camera channel inputs at the top of the page. The four inputs may be received by a video capture interface26. The video capture interface26may receive multiple simultaneous video inputs in the form of camera inputs or other video information, including television, digital video recorder, or media player inputs, to mention a few examples.

The video capture interface automatically captures and copies each input frame. One copy of the input frame is provided to the VAFF unit66and the other copy may be provided to VEFF unit68. The VEFF unit68is responsible for storing the video on the external memory, such as the memory22, shown inFIG. 1. The external memory may be coupled to an on-chip system memory controller/arbiter51in one embodiment. In some embodiments, the storage on the external memory may be for purposes of video encoding. Specifically, if one copy is stored on the external memory, it can be accessed by the video encoders32for encoding the information in a desired format. In some embodiments, a plurality of formats are available and the system may select a particular encoding format that is most desirable.

As described above, in some cases, video analytics may be utilized to improve the efficiency of the encoding process implemented by the video encoders32. Once the frames are encoded, they may be provided via the PCI Express bus36to the host system.

At the same time, the other copies of the input video frames are stored on the two dimensional matrix or main memory28. The VAFF may process and transmit all four input video channels at the same time. The VAFF may include four replicated units to process and transmit the video. The transmission of video for the memory28may use multiplexing. Due to the delay inherent in the video retrace time, the transfers of multiple channels can be done in real time, in some embodiments.

Storage on the main memory may be selectively implemented non-linearly or linearly. In conventional, linear addressing one or more locations on intersecting addressed lines are specified to access the memory locations. In some cases, an addressed line, such as a word or bitline, may be specified and an extent along that word or bitline may be indicated so that a portion of an addressed memory line may be successively stored in automated fashion.

In contrast, in two dimensional or non-linear addressing, both row and column lines may be accessed in one operation. The operation may specify an initial point within the memory matrix, for example, at an intersection of two addressed lines, such as row or column lines. Then a memory size or other delimiter is provided to indicate the extent of the matrix in two dimensions, for example, along row and column lines. Once the initial point is specified, the entire matrix may be automatically stored by automated incrementing of addressable locations. In other words, it is not necessary to go back to the host or other devices to determine addresses for storing subsequent portions of the memory matrix, after the initial point. The two dimensional memory offloads the task of generating addresses or substantially entirely eliminates it. As a result, in some embodiments, both required bandwidth and access time may be reduced.

Basically the same operation may be done in reverse to read a two dimensional memory matrix. Alternatively, a two dimensional memory matrix may be accessed using conventional linear addressing as well.

While an example is given wherein the size of the memory matrix is specified, other delimiters may be provided as well, including an extent in each of two dimensions (i.e. along word and bitlines). The two dimensional memory is advantageous with still and moving pictures, graphs, and other applications with data in two dimensions.

Information can be stored in the memory28in two dimensions or in one dimension. Conversion between one and two dimensions can occur automatically on the fly in hardware, in one embodiment.

In some embodiments, video encoding of multiple streams may be undertaken in a video encoder at the same time the multiple streams are also being subjected to analytics in the video analytics functional unit42. This may be implemented by making a copy of each of the streams in the video capture interface26and sending one set of copies of each of the streams to the video encoders32, while another copy goes to the video analytics functional unit42.

In one embodiment, a time multiplexing of each of the plurality of streams may be undertaken in each of the video encoders32and the video analytics functional unit42. For example, based on user input, one or more frames from the first stream may be encoded, followed by one or more frames from the second stream, followed by one or more streams from the next stream, and so on. Similarly, time multiplexing may be used in the video analytics functional unit42in the same way wherein, based on user inputs, one or more frames from one stream are subjected to video analytics, then one or more frames from the next stream, and so on. Thus, a series of streams can be processed at substantially the same time, that is, in one shot, in the video encoders and video analytics functional unit.

In some embodiments, the user can set the sequence of which stream is processed first and how many frames of each stream are processed at any particular time. In the case of the video encoders and the video analytics engine, as the frames are processed, they can be output over the PCI Express bus36.

The context of each stream in the video encoder may be retained in a register dedicated to that stream in the register set122, which may include registers for each of the streams. The register set122may record the characteristics of the encoding which have been specified in one of a variety of ways, including a user input. For example, the resolution, compression rate, and the type of encoding that is desired for each stream can be recorded. Then, as the time multiplexed encoding occurs, the video encoder can access the correct characteristics for the current stream being processed from the register116, for the correct stream.

Similarly, the same thing can be done in the video analytics functional unit42using the register set124. In other words, the characteristics of the video analytics processing or the encoding per stream can be recorded within the registers124and122with one register reserved for each stream in each set of registers.

In addition, the user or some other source can direct that the characteristics be changed on the fly. By “on the fly,” it is intended to refer to a change that occurs during analytics processing, in the case of the video analytics functional unit42or in the case of encoding, in the case of the video encoders32.

When a change comes in when a frame is being processed, the change may be initially recorded in shadow registers116, for the video encoders and shadow registers114, for the video analytics functional unit42. Then, as soon as the frame (or designated number of frames) is completed, the video encoder32checks to see if any changes have been stored in the registers116. If so, the video encoder transfers those changes over the path120to the registers122, updating the new characteristics in the registers appropriate for each stream that had its encoding characteristics changed on the fly.

Again, the same on the fly changes may be done in the video analytics functional unit42, in one embodiment. When an on the fly change is detected, the existing frames (or an existing set of work) may be completed using the old characteristics, while storing the changes in the shadow registers114. Then at an opportune time, after a workload or frame has completed processing, the changes may be transferred from the registers114over the bus118to the video analytics functional unit42for storage in the registers124, normally replacing the characteristics stored for any particular stream in separate registers among the registers124. Then, once the update is complete, the next processing load uses the new characteristics.

Thus, referring toFIG. 6, the sequence130may be implemented in software, firmware, and/or hardware. In software or firmware based embodiments, the sequence may be implemented by computer executed instructions stored in a non-transitory computer readable medium, such as an optical, magnetic, or semiconductor memory. For example, in the case of the video encoder32, the sequence may be stored in a memory within the encoder and, in the case of the analytics functional unit, they may be stored, for example in the pixel pipeline unit44, in one embodiment.

Initially, the sequence waits for user input of context instructions for encoding or analytics. The flow may be the same, in some embodiments, for analytics and encoding. Once the user input is received, as determined in diamond132, the context is stored for each stream in an appropriate register122or124, as indicated in block134. Then the time multiplexed processing begins, as indicated in block136. During that processing, a check at diamond138determines whether there has been any processing change instructions. If not, a check at diamond142determines whether the processing is completed. If not, the time multiplexed processing continues.

If a processing change has been received, it may be stored in the appropriate shadow registers114or116, as indicated in block140. Then, when a current processing task is completed, the change can be automatically implemented in the next set of operations, be it encoding, in the case of video encoders32or analytics, in the case of the video analytics functional unit42.

In some embodiments, the frequency of encoding may change with the magnitude of the load on the video encoder. Generally, the encoder runs fast enough that it can complete encoding of one frame before the next frame is read out of the memory. In many cases, the encoding engine may be run at a faster speed than needed to encode one frame or set of frames before the next frame or set of frames has run out of memory.

The context registers may store any necessary criteria for doing the encoding or analytics including, in the case of the video encoder, resolution, encoding type, and rate of compression. Generally, the processing may be done in a round robin fashion proceeding from one stream or channel to the next. The encoded data is then output to the Peripheral Components Interconnect (PCI) Express bus36, in one embodiment. In some cases, buffers associated with the PCI Express bus may receive the encoding from each channel. Namely, in some embodiments, a buffer may be provided for each video channel in association with the PCI Express bus. Each channel buffer may be emptied to the bus controlled by an arbiter associated with the PCI Express bus. In some embodiments, the way that the arbiter empties each channel to the bus may be subject to user inputs.

Thus, referring toFIG. 3, a system for video capture may be implemented in hardware, software, and/or firmware. Hardware embodiments may be advantageous, in some cases, because they may be capable of greater speeds.

As indicated in block72, the video frames may be received from one or more channels. Then the video frames are copied, as indicated in block74. Next, one copy of the video frames is stored in the external memory for encoding, as indicated in block76. The other copy is stored in the internal or the main memory28for analytics purposes, as indicated in block78.

Referring next to the two dimensional matrix sequence80, shown inFIG. 4, a sequence may be implemented in software, firmware, or hardware. Again, there may be speed advantages in using hardware embodiments.

Initially, a check at diamond82determines whether a store command has been received. Conventionally, such commands may be received from the host system and, particularly, from its central processing unit12. Those commands may be received by a dispatch unit34, which then provides the commands to the appropriate units of the video analytics engine20, used to implement the command. When the command has been implemented, in some embodiments, the dispatch unit reports back to the host system.

If a store command is involved, as determined in diamond82, an initial memory location and two dimensional size information may be received, as indicated in block84. Then the information is stored in an appropriate two dimensional matrix, as indicated in block86. The initial location may, for example, define the upper left corner of the matrix. The store operation may automatically find a matrix within the memory28of the needed size in order to implement the operation. Once the initial point in the memory is provided, the operation may automatically store the succeeding parts of the matrix without requiring additional address computations, in some embodiments.

Conversely, if a read access is involved, as determined in diamond88, the initial location and two dimensional size information is received, as indicated in block90. Then the designated matrix is read, as indicated in block92. Again, the access may be done in automated fashion, wherein the initial point may be accessed, as would be done in conventional linear addressing, and then the rest of the addresses are automatically determined without having to go back and compute addresses in the conventional fashion.

Finally, if a move command has been received from the host, as determined in block94, the initial location and two dimensional size information is received, as indicated in block96, and the move command is automatically implemented, as indicated in block98. Again, the matrix of information may be automatically moved from one location to another, simply by specifying a starting location and providing size information.

Referring back toFIG. 2, the video analytics functional unit42may be coupled to the rest of the system through a pixel pipeline unit44. The unit44may include a state machine that executes commands from the dispatch unit34. Typically, these commands originate at the host and are implemented by the dispatch unit. A variety of different analytics units may be included based on application. In one embodiment, a convolve unit46may be included for automated provision of convolutions.

The convolve command may include both a command and arguments specifying a mask, reference or kernel so that a feature in one captured image can be compared to a reference two dimensional image in the memory28. The command may include a destination specifying where to store the convolve result.

In some cases, each of the video analytics units may be a hardware accelerator. By “hardware accelerator,” it is intended to refer to a hardware device that performs a function faster than software running on a central processing unit.

In one embodiment, each of the video analytics units may be a state machine that is executed by specialized hardware dedicated to the specific function of that unit. As a result, the units may execute in a relatively fast way. Moreover, only one clock cycle may be needed for each operation implemented by a video analytics unit because all that is necessary is to tell the hardware accelerator to perform the task and to provide the arguments for the task and then the sequence of operations may be implemented, without further control from any processor, including the host processor.

Other video analytics units, in some embodiments, may include a centroid unit48that calculates centroids in an automated fashion, a histogram unit51that determines histograms in automated fashion, and a dilate/erode unit52.

The dilate/erode unit52may be responsible for either increasing or decreasing the resolution of a given image in automated fashion. Of course, it is not possible to increase the resolution unless the information is already available, but, in some cases, a frame received at a higher resolution may be processed at a lower resolution. As a result, the frame may be available in higher resolution and may be transformed to a higher resolution by the dilate/erode unit52.

The Memory Transfer of Matrix (MTOM) unit54is responsible for implementing move instructions, as described previously. In some embodiments, an arithmetic unit56and a Boolean unit58may be provided. Even though these same units may be available in connection with a central processing unit or an already existent coprocessor, it may be advantageous to have them onboard the video analytics engine20, since their presence on-chip may reduce the need for numerous data transfer operations from the video analytics engine20to the host and back. Moreover, by having them onboard the video analytics engine20, the two dimensional matrix or main memory may be used in some embodiments.

An extract unit60may be provided to take vectors from an image. A lookup unit62may be used to lookup particular types of information to see if it is already stored. For example, the lookup unit may be used to find a histogram already stored. Finally, the subsample unit64is used when the image has too high a resolution for a particular task. The image may be subsampled to reduce its resolution.

In some embodiments, other components may also be provided including an I2C interface38to interface with camera configuration commands and a general purpose input/output device40connected to all the corresponding modules to receive general inputs and outputs and for use in connection with debugging, in some embodiments.

Referring toFIG. 5, an analytics assisted encoding scheme100may be implemented, in some embodiments. The scheme may be implemented in software, firmware and/or hardware. However, hardware embodiments may be faster. The analytics assisted encoding may use analytics capabilities to determine what portions of a given frame of video information, if any, should be encoded. As a result, some portions or frames may not need to be encoded in some embodiments and, as one result, speed and bandwidth may be increased.

In some embodiments, what is or is not encoded may be case specific and may be determined on the fly, for example, based on available battery power, user selections, and available bandwidth, to mention a few examples. More particularly, image or frame analysis may be done on existing frames versus ensuing frames to determine whether or not the entire frame needs to be encoded or whether only portions of the frame need to be encoded. This analytics assisted encoding is in contrast to conventional motion estimation based encoding which merely decides whether or not to include motion vectors, but still encodes each and every frame.

In some embodiments of the present invention, successive frames are either encoded or not encoded on a selective basis and selected regions within a frame, based on the extent of motion within those regions, may or may not be encoded at all. Then, the decoding system is told how many frames were or were not encoded and can simply replicate frames as needed.

Referring toFIG. 5, a first frame or frames may be fully encoded at the beginning, as indicated in block102, in order to determine a base or reference. Then, a check at diamond104determines whether analytics assisted encoding should be provided. If analytics assisted encoding will not be used, the encoding proceeds as is done conventionally.

If analytics assisted encoding is provided, as determined in diamond104, a threshold is determined, as indicated in block106. The threshold may be fixed or may be adaptive, depending on non-motion factors such as the available battery power, the available bandwidth, or user selections, to mention a few examples. Next, in block108, the existing frame and succeeding frames are analyzed to determine whether motion in excess of the threshold is present and, if so, whether it can be isolated to particular regions. To this end, the various analytics units may be utilized, including, but not limited to, the convolve unit, the erode/dilate unit, the subsample unit, and the lookup unit. Particularly, the image or frame may be analyzed for motion above a threshold, analyzed relative to previous and/or subsequent frames.

Then, as indicated in block110, regions with motion in excess of a threshold may be located. Only those regions may be encoded, in one embodiment, as indicated in block112. In some cases, no regions on a given frame may be encoded at all and this result may simply be recorded so that the frame can be simply replicated during decoding. In general, the video encoder provides information in a header or other location about what frames were encoded and whether frames have only portions that are encoded. The address of the encoded portion may be provided in the form of an initial point and a matrix size in some embodiments.

FIGS. 3, 4, and 5are flow charts which may be implemented in hardware. They may also be implemented in software or firmware, in which case they may be embodied on a non-transitory computer readable medium, such as an optical, magnetic, or semiconductor memory. The non-transitory medium stores instructions for execution by a processor. Examples of such a processor or controller may include the analytics engine20and suitable non-transitory media may include the main memory28and the external memory22, as two examples.

As shown inFIG. 1, the video analytics engine20is coupled to a host including the central processing unit12. The video analytics engine20executes instructions independently from the host central processing unit12. However, the host central processing unit must feed the video analytics engine20both data and instructions and it must receive results of operations. To accomplish these tasks, without the overhead incurred in polling for completion of instruction execution, intelligent message signaled interrupts (MSI-X) may be applied in some embodiments.

To ensure data integrity for instructions that require a large data transfer to the host, the video analytics engine20uses a RAISE instruction that generates an MSI-X interrupt. The MSI interrupt that results not only serves as an interrupt but also carries additional information in the message data field of the interrupt to reduce the overhead involved in servicing the interrupt. Furthermore, the intelligent MSI-X interrupt controller holds off the acknowledge to the RAISE interrupt request from the instruction dispatch unit until the data transferred to the host is complete. This mechanism may ensure that an interrupt for a RAISE instruction is sent only after a successful completion of the READ or RMD instruction through the Peripheral Component Interconnect Express bus36.

The structure of the MSI-X interface is as follows in one embodiment where IC is the video analytics engine20, O is Out and I is In and size is in bytes.

Direc-tionw.r.t.PortSizeICDescriptionmisx_addr640The address value for theMSI-Xmisx_data320The data value for the MSI-Xmsi_req10Request from the applicationto send an MSI when MSI isenabled.Once asserted, msi_req mustremain asserted until the EPCasserts msi_grantmis_tc30Traffic Class of the MSI(-X)request, valid when msi_reqis assertedmis_grant1IOne-cycle pulse that indicatesthat the EPChas accepted therequest to send an MSI(-X).After asserting msi_grant forone cycle, the EPC does notwait for msi_req to be deas-serted then reasserted togenerate another MSI. Ifmsi_req remains assertedafter the EPC assertsmsi_grant for one cycle,the EPC will generate an-other MSI.Cfg_msix_en1IThe MSI-X Enable bit of theMSI-X Control register in theMSI-X Capability structureCfg_msix_func_mask1IThe IC Mask bit of the MSI-XControl register in the MSI-XCapability structure

Referring toFIG. 7, the interrupt controller300receives clocks from the various components that provide interrupts and receives reset signals from those same devices. A configuration and status register (CSR) decode302receives CSR inputs. It provides a signal to MSI-X interface304. It also provides a decode signal to the legacy interrupt pending register306. The MSI-X interface receives interrupts from a resync unit310. The resync unit310receives interrupts from functional units such as a video encoder (VE) the memory matrix (MM), the video capture interface (VCI), the external memory (DDR), the I2c bus (I2C), the general purpose input/output (GPIO), the dispatch unit (DU) and receives the dispatch unit RAISE signal.

The Peripheral Component Interconnect dispatch unit write done signal is provided to a dispatch unit RAISE controller308. The controller308provides a dispatch unit write done acknowledge signal and receives and sends signals to the resync unit310.

Thus referring toFIG. 8, timing for the various signals is illustrated. The core clock is shown at the top followed by the video encoder MSI request. Next the timing of the video encoder MSI grant is shown. This is a one-cycle pulse indicating that the request to send an MSI-x was accepted. Following this, the MSI-X address signal is illustrated for one embodiment. This is followed by the MSI-X data signal. Finally, the video encoder MSI traffic class (tc) signal is illustrated followed by the configuration (CFG) MSI-X encoder signal. A traffic class is a type of system traffic in PCI Express, that may be assigned to a supported virtual channel for flow control purposes. The traffic class of the MSI-X request is valid when the MSI request is asserted. The cfg_msix_en is for the MSI-X enable bit of the MSI-X control register in the MSI-X capability structure.

Referring toFIG. 9, a sequence400for implementing an interrupt controller may be implemented in software, firmware and/or hardware. In software and firmware embodiments it may be implemented by computer executed instructions stored in a non-transitory computer readable medium such as a magnetic, optical or semiconductor storage. For example, in one embodiment, the instructions may be implemented within the interrupt controller300.

The sequence may begin by detecting an interrupt as indicated in diamond402. Then in block404, the interrupt may be indicated. The interrupt may be accompanied by an address value, data value, and a traffic class as indicated in block406to assist in servicing the interrupt.

Then the check at diamond408determines whether the data transfer is complete. If so, an acknowledge may be sent as indicated in block410. Otherwise, the acknowledge is held off as indicated in block412.

The graphics processing techniques described herein may be implemented in various hardware architectures. For example, graphics functionality may be integrated within a chipset. Alternatively, a discrete graphics processor may be used. As still another embodiment, the graphics functions may be implemented by a general purpose processor, including a multicore processor.