The lifetime of a stand-alone media recorder is a function of both the battery size and flash memory size. In this paper, we present a power management framework for media recorders that significantly enhances their lifetime while minimizing the flash memory usage and maintaining the same level of recording quality. This is achieved by implementing a mixture of encoding algorithms of different complexities that generate data with different compression ratios, and in turn balancing the energy consumption and the flash memory usage. The proposed method can be effectively employed on a direct battery drive system which does not use a DC-DC converter. The gradual drop of the battery voltage of such system is compensated by operating algorithms of lower complexity more and more. For a speech encoding application where a mixture of ADPCM (low complexity) and MP3 (high complexity) is used, the proposed algorithm achieves 70% more lifetime than a DC-DC converter with a highest clock frequency, and 20% more lifetime than even a DC-DC converter with the optimal clock frequency.
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