| Audio system widely applies in field of embedded system. The requirements of every embedded products are different.To communication products, the needs in performance is higher than any other products. In network video telephone terminal, audio system's realization is based on Analog Device incorporation's dual core processor ADSP-BF561 and entirely open source's uClinux operation system. The audio system is developed in ADI's debug tool and integrated developing environment Visual DSP++, which is designed for Blackfin series processors.In developing process, audio system's realization is separated into three parts:audio gathering module,audio export module and network module. Audio software's design make the best of the processor ADSP-BF561's characteristic in dual core.The network video telephone terminal realizes the audio gathering and encoding in one blackfin core and audio exporting and decoding in another blackfin core. At the same time, the communication mechanism of the dual core is realized.Audio gathering module is been used to realize the audio signal's gathering and encoding, including equipment's initialization, interrupt's disposition and calling of audio encoding and so on. Audio exporting module is been used in audio package's decoding and exporting, including audio decoding code's realization, UDA1380 driver's realization, and so on.In course of audio system's realization, aim at the questions of in audio data's transferring, such as delay, wobble, echo and package's dropping, the audio system is been optimized. Including audio encode's selection, take the measure of selecting the fittest, and needing of resource fewest's encoding measure; realizing the circle buffer for delay and wobble; realizing echo eliminating module for the echo disposing and adopting the measure of audio and video synchronization for receiveing the better talking effect. These measures's realization lets the network video telephone terminal receive the preferably talking effect. |
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