The embedded image processing systems like smartphones and digital cameras have tight limits on storage, computation power, network connectivity, and battery usage. These limitations make it important to ensure efficient image coding. In the article, we present a novel heap-based priority queue structure employed by an Adaptive Scanning of Wavelet Data scheme (ASWD) targeting an embedded platform. ASWD is a context modeling block implemented via priority queues in a wavelet-based image coder to reorganize the wavelet coefficients into locally stationary sequences. The architecture we propose exploits efficient use of FPGA’s on-chip dual-port memories in an adaptive manner. Innovations of index-aware system linked to each element in the queue makes the location of queue element traceable in the heap as per the requirements of the ASWD algorithm. Moreover, use of 4-port memories along with intelligent data concatenation of queue elements yielded in a cost effective enhanced memory access. The memory ports are adaptively assigned to different units during different processing phases in a manner to optimally take advantage of memory access required by that phase. The architectural innovations can also be exploited in other applications that require efficient hardware implementations of generic priority queue or classical sorting applications which sort into the index. We designed and validated the hardware on an Altera’s Stratix IV FPGA as an IP accelerator in a Nios II processor based System on Chip. We show that our architecture at 150MHz can provide 45X speedup compared to an embedded ARM Cortex-A9 processor at 666MHz targeting the throughput of 10MB/s.

We present a hardware architecture of a heapsort algorithm, the sorting is employed in a subband coding block of a wavelet-based image coder termed Öktem image coder [1]. Although this coder provides good image quality, the sorting is time consuming, and is application specific, as the sorting is repetitively used for different volume of data in the subband coding, thus a simple hardware implementation with fixed sorting capacity will be difficult to scale during runtime. To tackle this problem, the time/power efficiency and the sorting size flexibility have to be taken in to account. We proposed an improved FPGA heapsort architecture based on Zabołotny's work [2] as an IP accelerator of the image coder. We present a configurable architecture by using adaptive layer enable elements so the sorting capacity could be adjusted during runtime to efficiently sort different amount of data. With the adaptive memory shutdown, our improved architecture provides up to 20.9% power reduction on the memories compared to the baseline implementation. Moreover, our architecture provides 13x speedup compared to ARM CortexA9.

This paper presents an adaptive heap sort architecture for an image coding implementation on FPGA, which specifically addresses the issue of sorting different amount of data located in each subband during the coding. The proposed sorting architecture is easily scalable. Performance of the sorter only depends on the amount of data sorted. The efficient usage of dual port memories yields high throughput up to 50 Msamples/s and their adaptive trigger/shutdown provide the average dynamic power reduction up to 20.9%. We designed this architecture and incorporated it in our Adaptive Scanning of Wavelet Data (ASWD) module which reorganizes the wavelet coefficients into locally stationary sequences for a wavelet-based image encoder. We validated the hardware on an Altera's Stratix IV FPGA as an IP accelerator in a Nios II processor based System on Chip. The architectural innovations can also be exploited in other applications that require high throughput and scalable sorting. Our experiments show that compared to an embedded ARM CortexA9 processor running at 666 MHz, our architecture at 100 MHz can provide around 13X speedup while consuming 242 mW average core dynamic power.

In this paper we present a novel high performance, low resource utilization and power efficient hardware architecture of an entropy coding scheme. The proposed architecture implements the Hierarchical Enumerative Coding algorithm (HENUC) on an embedded soft-processor based System-on-Chip, in which HENUC is an integral part of a wavelet based encoder oriented for locally stationary image source. Though HENUC has been implemented on an embedded DSP architecture before, the throughput was low. This paper proposes an optimized parallel architecture for HENUC, which is validated on a Terasic DE4-230 board containing Altera Stratix IV FPGA. Our implementation at 100MHz provides 5.7x speedup over Intel Xeon 8-core CPU and 12.3x speedup over TI DSP for 512 × 512 image while consuming less than 500 mw FPGA core power.

A comparative study of Hierarchical Enumerative Coding (HENUC) for FPGA and DSP implementation is presented. HENUC is a lossless fixed-point entropy coding algorithm employed by a wavelet-based image encoder, which provides good compression performance for the locally stationary image data. It has been implemented in our previous work on an Altera's 40nm Stratix IV EP4SGX230 FPGA as a hardware IP accelerator in a Nios II based system. In this paper, we implemented it on a Texas Instruments's (TI) 40nm Integra C6A816x/AM389x DSP. We present experimental results regarding the execution time, resource utilization and core power consumption of the two implementations and we evaluate their throughput and power efficiency. Our results show that a highly parallelized FPGA implementation at 100MHz is 12.3x faster than a highly tuned DSP implementation running at 1.5 GHz and consumes 2.4x less power, they also show that the proposed algorithm is more suitable for hardware implementation.