The MPEG-4 standard has already been established, well accepted and is being widely used by content creators, developers, manufacturers,
providers of services and end users. Industry leaders have come together to guarantee interoperability. Amongst the video standards, the MPEG-4 video Advanced Simple Profile (ASP) has found wide acceptance and the need for real-time low cost MPEG-4 video ASP encoding solutions isappropriate for certain markets.
Embedded multimedia systems, such as programmable VLIW-based chips offer flexibility and functionality, and are very suitable platforms for deployment of real-time multimedia applications. The Equator BSP-15 is one such single chip platform. Enabling technologies for
such embedded multimedia systems require very careful and often creative considerations of cost versus performance.
To this end, we have designed and developed a real-time MPEG-4 video ASP encoder at Level 5 on an Equator BSP-15 chip. This paper
describes our experiences with the design considerations and some
implementation issues along with some proposed solutions. The experimental results show the feasibility of these solutions to obtain very good performance on low-cost embedded systems.
In this work, our goal is to develop a real-time software- based H.263 video encoder using a single-processor system. This requires optimizing the execution speed of the code which, in turn, needs optimization at various design phases, including algorithmic enhancements, efficient implementations of these algorithms, and taking advantage of certain architectural features of the machine. We present an H.263 video encoder implemented on a single Sun UltraSPARC-1 workstation. In order to exploit the architectural features of the machine, we make use of a low-level machine primitive, namely, Sun UltraSPARC's Visual Instruction Set (VIS). Using VIS, we accelerate the computation in a SIMD fashion, increase the utilization of available registers in the processor, and remove register contentions between data and control variables. We have achieved a reasonably high frame encoding rate of more than 12 frames per second for QCIF resolution of video with high perceptual quality, which is sufficient for most of the GSTN-based video telephony applications. Extensive benchmarking experiments have been carried out to study the performance of the encoder. We have taken into account the effects of the optional H.263 coding modes on PSNR, bit rate and encoding speed. Based on these effects, suggestions are made to decide the optimum coding options.
KEYWORDS: Computer programming, Video, Video compression, Video surveillance, Video coding, Sun, Parallel processing, Telecommunications, Data communications, Asynchronous transfer mode
In this paper, we present a software based H.263 video encoder using a cluster of workstations. H.263 is an international standard for video coding using low bitrate communication. Due to a high computational cost, a real-time software based codec (specially encoder) is impossible to implement using currently available single-processor systems. Parallel processing using multiple computers, however, is a natural way of implementing a software-based real-time codec. A cluster of workstations is analogous to a parallel machine consisting of several processors each with its own memory and is a cost-effective computing platform. The workstations connected via an ATM switch use message passing interface (MPI) library for communication. Our implementation is based on a data-parallel approach in which parallelism is exploited within each frame of the video on a macroblock basis. Since the encoder is implemented in software it provides flexibility to enhance performance through modifications and improvements in various components. The encoder can be used with various numbers of processors connected via any physical hardware topology, and its peformance scales accordingly. It provides options for user-defined parameters such as the number of processors, the size of motion search window, quantization parameter, bit- rate, etc. The experimental results indicate that our approach is suitable for real-time applications such as video telephony on conventional analog telephone lines. An encoding rate of 30 frames/sec. (with QCIF format) is achieved using 12 workstations.
KEYWORDS: Computer programming, Video, Video compression, Standards development, Sun, Video coding, Motion estimation, Video surveillance, Data communications, Distributed computing
Traditionally, real-time video compression due to its enormous computing requirement has been done using the special-purpose hardware. On the other hand, software-based solutions have been primarily intended for non real-time applications. In this paper, we present a portable and scalable implementation of the MPEG-2 video encoder, using parallel processing, that can be used for both real-time and non real-time applications. The portability allows it to run on a wide variety of platforms including a number of high-performance parallel computers as well as networks of workstations. The scalability allows the user to control the parallelism enabling it to run on a few fast workstations using a coarse granularity or on a massively parallel architecture using a fine grained granularity. An important feature of our implementation is that we use a data-parallel approach and exploit parallelism within each frame, unlike previous parallel video coding implementations. This makes our encoder suitable for real-time applications where the complete video sequence may not be present on the disk and may become available on a frame-by-frame basis with time. The encoder also provides control over various parameters such as number of processors, size of motion-search window, buffer management and bit rate. Our implementation is flexible and allows inclusion of fast and new algorithms for different stages of the encoder, replacing current algorithms. Experimental results have been conducted on two parallel processing systems: the Intel Paragon XP/S and the Intel iPSC/860 hypercube. Networks of workstations used include the SUN and HP, connected via the Ethernet and FDDI, respectively. Comparisons of execution times, speedups as well as frame encoding rates on these systems are provided. Using maximum parallelism by dividing one block per processor, an encoding rate higher than real- time (30 frames/sec) has been achieved on the Intel Paragon.
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