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这个示例代码实现了基于FFmpeg-0.10 SDK的音频重采样，也可用于实现定点转浮点计算。

1. 声明

/*  ffmpeg_sdk.h */#include 
   
    #include 
    
     #ifdef __cplusplusextern "C" {#endif#include "libavutil/imgutils.h"#include "libavutil/opt.h"#include "libavcodec/avcodec.h"#include "libavutil/mathematics.h"/* open log */#include "libavutil/log.h"/* audio resample */#include "libswresample/swresample.h"/* end */#ifdef __cplusplus}#endifclass FFmpegSDK{public:FFmpegSDK();~FFmpegSDK();#define INPUT_AUDIO_CHANNEL_LAYOUT   AV_CH_LAYOUT_MONO#define INPUT_AUDIO_SAMPLE_FMT            AV_SAMPLE_FMT_S16#define INPUT_AUDIO_SAMPLE_RATE          16000private:    SwrContext     *m_swrctx;public:    int32_t      init_swresample(int32_t in_audio_channel_layout,                                  enum AVSampleFormat in_audio_sample_fmt, int32_t in_audio_sample_rate);    int32_t      destroy_swrsample();    int32_t      swresample_doing(uint8_t** out_sample_buf, int32_t out_sample_cnt,                                 const uint8_t** in_sample_buf, int32_t in_sample_cnt);    };}
    
   

2. 定义

/*  ffmpeg_sdk.cpp */int32_t FFmpegSDK::init_swresample(int32_t in_audio_channel_layout,         enum AVSampleFormat in_audio_sample_fmt, int32_t in_audio_sample_rate){    m_swrctx = swr_alloc();    if (m_swrctx == NULL){        ERROR_LOG("Allocate swresample failed!\n");        return -1;    }#if LIBSWRESAMPLE_VERSION_MINOR >= 17  // #else    m_swrctx = swr_alloc_set_opts(m_swrctx,            m_avctx->channel_layout,            m_avctx->sample_fmt,            m_avctx->sample_rate,            in_audio_channel_layout,            in_audio_sample_fmt,            in_audio_sample_rate,            0, NULL);#endif    int32_t ret = swr_init(m_swrctx);    if (ret < 0){        ERROR_LOG("swr_init(->) failed!\n");        return -1;    }    return 0;}int32_t FFmpegSDK::destroy_swrsample(){    return 0;}int32_t FFmpegSDK::swresample_doing(uint8_t** out_sample_buf, int32_t out_sample_cnt,             const uint8_t** in_sample_buf, int32_t in_sample_cnt){    int32_t len = 0;    len = swr_convert(m_swrctx, out_sample_buf, out_sample_cnt,                 in_sample_buf, in_sample_cnt);    if (len  < 0){        char errmsg[1024];        av_strerror(len, errmsg, sizeof(errmsg));        ERROR_LOG("swr_convert!(%d)(%s)", len, errmsg);         return len;    }    return 0;}

3. 调用 

int FFmpegSDK::init(){     ret = init_swresample(INPUT_AUDIO_CHANNEL_LAYOUT,            INPUT_AUDIO_SAMPLE_FMT,            INPUT_AUDIO_SAMPLE_RATE);    if (ret < 0){        ERROR_LOG("init swresample failed!");        return false;    }    。。。}int FFmpegSDK::run(){        AVCodecContext *m_avctx;    。。。    m_avctx->channel_layout = AV_CH_LAYOUT_MONO;    m_avctx->sample_fmt       = AV_SAMPLE_FMT_FLT;    m_avctx->sample_rate      = 16000;    float *out_buf= new float[1024];    memset(out_buf, 0, 1024 * sizeof(float));     。。。     ret = swresample_doing((uint8_t**)&out_buf, 1024,                (const uint8_t**)&in_buf, 1024);    。。。}

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