A configurable processor core can be used to build an audio processor that has both high-performance and low-power characteristics of DSP and good control capabilities of a general-purpose processor. Tensilica's Hitens audio engine based on Xtensa is an example of this type of processor. The HiFi audio processor is based on the 32-bit Xtensa V processor core and has 24-bit audio-specific instructions. The processor core has been used in a variety of products, including mobile phones, portable audio players, camcorders, digital cameras, and personal video recording (PVR). Figure 1: HiFi 2 instruction format HiFi 2 audio engine expansion The Hardware added to the Xtensa LX processor includes two MAC units. Each MAC unit can perform 24 & TImes; 24-bit and 32 & TImes; 16-bit multiplication. Both MAC units are pipelined, so each clock cycle can produce a new execution result. The added hardware also includes a Huffman encoder and decoder, a bit stream processor, and two special register files for processing 24-bit audio data. One of the register files includes eight 48-bit registers, and each register can store two 24-bit data values; the other register file includes four 56-bit registers to store the extended precision calculation results generated by the two MAC units. as shown in picture 2. Figure 2: HiFi 2 structure diagram The performance results of the digital audio codec algorithm ported to the Xtensa HiFi 2 audio engine structure show that the design requires only a small processor bandwidth to support high-quality audio codec. For example, the MP3 decoder only needs 13 ~ 15MHz processor bandwidth when playing music stored in 48kHz / 128kbps stereo format. At a similar bit rate, the MP3 encoder only requires a processor bandwidth of 38-40MHz. AAC-LC encoder / decoder and WMA decoder can also obtain similar results. Arcade Game Console,game console,video game consoles,arcade games console Guangzhou Ruihong Electronic Technology CO.,Ltd , https://www.callegame.com
The introduction of Tensilica's Xtensa LX configurable processor can improve the performance of the original HiFi audio engine and provide users with a more powerful audio processor called Xtensa HiFi 2 audio engine. The engine can use narrower bandwidth (and therefore lower power consumption and energy) to run more complex digital audio codec algorithms. The Xtensa LX processor has certain configurable features that can allow these improvements.
In particular, the Xtensa LX processor has a feature called FLIX (Variable Length Instruction Extension), which allows the processor to mix existing 16-bit and 24-bit Xtensa instructions to generate custom wide instructions. Each FLIX format instruction can put multiple independent operations into the operation slot in each wide instruction word. The Xtensa HiFi 2 audio engine expansion of the Xtensa LX processor adds more than 300 dedicated audio DSP instructions, including 24-bit MAC (multiply / accumulate) instructions and stream encoding instructions. The introduction of these instructions greatly reduces the complexity of audio codec algorithms The number of execution cycles.
Some new dedicated audio instructions are 24-bit instructions, and some are 64-bit FLIX format instructions. The HiFi 2 audio engine's FLIX format instructions include two operation slots. All HiFi 2 audio engine instruction extensions can directly use the compiler generated with the processor generated by Tensilica's automated Xtensa Processor Generator. As shown in Figure 1. 
The Xtensa LX processor uses a wide range of clock gating technology, which surpasses the technology used in the Xtensa V processor design to reduce power consumption. This feature, together with the low clock rate required to implement digital audio encoding and decoding on the Xtensa HiFi2 audio engine architecture, results in a very efficient audio processor. The Xtensa LX processor with Xtensa HiFi 2 audio engine extension uses TSMC's 130nm LV manufacturing process, and the power consumption is only 91μW / MHz; while the power consumption of the original HiFi audio engine based on the Xtensa V processor is 207μW / MHz.
When the AAC-LC encoder algorithm is executed, the HiFi 2 audio engine operating frequency is 38MHz; while the original Xtensa HiFi audio engine operating frequency is 85MHz. As a result of these improvements, the power consumption of the Xtensa HiFi 2 audio engine is 3.5mW when executing the AAC-LC encoder algorithm; the original Xtensa HiFi audio engine consumes 17.6mW when performing the same task. Although the power consumption of the original Xtensa HiFi audio engine is already very low, the power consumption of the Xtensa HiFi 2 audio engine is still five times lower than the original.
The Xtensa HiFi 2 audio engine architecture has three advantages over the original successful Xtensa HiFi audio engine. First, the Xtensa HiFi 2 audio engine reduces the processor bandwidth for advanced digital audio encoding and decoding. Secondly, when implementing these digital audio codec algorithms, the power consumption is reduced, due to the reduced bandwidth required, and because the Xtensa LX processor on which Xtensa HiFi 2 is based has more than the previous Xtensa V processor Extended clock gating. Finally, the Xtensa HiFi 2 audio engine architecture based on Xtensa LX requires fewer gates than the original Xtensa HiFi engine based on the Xtensa V processor (at 200MHz clock rate, the number of integrated processor gates is reduced About 20%).
By adding dedicated audio instructions, Tensilica's Xtensa LX processor can provide an efficient, low-power, high-performance platform for building digital audio products. Such a platform can execute a variety of audio encoding and decoding algorithms, and can perform control tasks beyond traditional DSPs if needed. Moreover, Xtensa HiFi 2 audio engine can provide much lower cost and clock frequency with the same performance. Therefore, the power consumption level can be greatly reduced compared to a general-purpose CPU.