FFmpeg4.0笔记：封装ffmpeg的音频重采样功能类CSwr

Github

https://github.com/gongluck/FFmpeg4.0-study/tree/master/Cff

CSwr.h

/*******************************************************************

*  Copyright(c) 2019

*  All rights reserved.

*

*  文件名称:    CSwr.h

*  简要描述:    重采样

*

*  作者:  gongluck

*  说明:

*

*******************************************************************/

#ifndef __CSWR_H__

#define __CSWR_H__

#ifdef __cplusplus

extern "C"

{

#endif

#include <libswresample/swresample.h>

#ifdef __cplusplus

}

#endif

#include <string>

#include <mutex>

class CSwr

{

public:

    virtual ~CSwr();

    // 状态

    enum STATUS { STOP, LOCKED };

    // 设置源参数

    bool set_src_opt(int64_t layout, int rate, enum AVSampleFormat fmt, std::string& err);

    // 设置目标参数

    bool set_dst_opt(int64_t layout, int rate, enum AVSampleFormat fmt, std::string& err);

    // 锁定设置

    bool lock_opt(std::string& err);

    // 解除锁定

    bool unlock_opt(std::string& err);

    // 转换(out_count,in_count is per channel's samples)

    int convert(uint8_t** out, int out_count, const uint8_t** in, int in_count, std::string& err);

private:

    STATUS status_ = STOP;

    std::recursive_mutex mutex_;

    SwrContext* swrctx_ = nullptr;

    AVSampleFormat src_sam_fmt_ = AV_SAMPLE_FMT_NONE;

    AVSampleFormat dst_sam_fmt_ = AV_SAMPLE_FMT_NONE;

    int64_t src_layout_ = AV_CH_LAYOUT_MONO;

    int64_t dst_layout_ = AV_CH_LAYOUT_MONO;

    int src_rate_ = 0;

    int dst_rate_ = 0;

};

#endif//__CSWR_H__

CSwr.cpp

/*******************************************************************

*  Copyright(c) 2019

*  All rights reserved.

*

*  文件名称:    CSwr.cpp

*  简要描述:    重采样

*

*  作者:  gongluck

*  说明:

*

*******************************************************************/

#include "common.h"

#include "CSwr.h"

CSwr::~CSwr()

{

    std::string err;

    unlock_opt(err);

}

bool CSwr::set_src_opt(int64_t layout, int rate, enum AVSampleFormat fmt, std::string& err)

{

    LOCK();

    CHECKSTOP(err);

    err = "opt succeed.";

    src_layout_ = layout;

    src_rate_ = rate;

    src_sam_fmt_ = fmt;

    return true;

}

bool CSwr::set_dst_opt(int64_t layout, int rate, enum AVSampleFormat fmt, std::string& err)

{

    LOCK();

    CHECKSTOP(err);

    err = "opt succeed.";

    dst_layout_ = layout;

    dst_rate_ = rate;

    dst_sam_fmt_ = fmt;

    return true;

}

bool CSwr::lock_opt(std::string& err)

{

    LOCK();

    CHECKSTOP(err);

    err = "opt succeed.";

    swrctx_ = swr_alloc_set_opts(swrctx_, dst_layout_, dst_sam_fmt_, dst_rate_, src_layout_, src_sam_fmt_, src_rate_, 0, nullptr);

    if (swrctx_ == nullptr)

    {

        err = "swr_alloc_set_opts return nullptr.";

        return false;

    }

    int ret = swr_init(swrctx_);

    CHECKFFRET(ret);

    status_ = LOCKED;

    return true;

}

bool CSwr::unlock_opt(std::string& err)

{

    LOCK();

    err = "opt succeed.";

    swr_free(&swrctx_);

    status_ = STOP;

    src_sam_fmt_ = AV_SAMPLE_FMT_NONE;

    dst_sam_fmt_ = AV_SAMPLE_FMT_NONE;

    src_layout_ = AV_CH_LAYOUT_MONO;

    dst_layout_ = AV_CH_LAYOUT_MONO;

    src_rate_ = 0;

    dst_rate_ = 0;

    return true;

}

int CSwr::convert(uint8_t** out, int out_count, const uint8_t** in, int in_count, std::string& err)

{

    LOCK();

    CHECKNOTSTOP(err);

    err = "opt succeed.";

    int ret = swr_convert(swrctx_, out, out_count, in, in_count);

    CHECKFFRET(ret);

    return ret;

}

测试

// 音频重采样

void test_swr()

{

    bool ret = false;

    std::string err;

    std::ifstream pcm("in.pcm", std::ios::binary);

    CSwr swr;

    // 分配音频数据内存

    uint8_t** src = nullptr;

    int srclinesize = 0;

    uint8_t** dst = nullptr;

    int dstlinesize = 0;

    // 分配音频数据内存

    int srcsize = av_samples_alloc_array_and_samples(&src, &srclinesize, 2, 44100, AV_SAMPLE_FMT_S16, 1);

    int dstsize = av_samples_alloc_array_and_samples(&dst, &dstlinesize, 2, 48000, AV_SAMPLE_FMT_S16P, 1);

    // 获取样本格式对应的每个样本大小(Byte)

    int persize = av_get_bytes_per_sample(AV_SAMPLE_FMT_S16P);

    // 获取布局对应的通道数

    int channel = av_get_channel_layout_nb_channels(AV_CH_LAYOUT_STEREO);

    ret = swr.set_src_opt(AV_CH_LAYOUT_STEREO, 44100, AV_SAMPLE_FMT_S16, err);

    TESTCHECKRET(ret);

    ret = swr.set_dst_opt(AV_CH_LAYOUT_STEREO, 48000, AV_SAMPLE_FMT_S16P, err);

    TESTCHECKRET(ret);

    ret = swr.lock_opt(err);

    TESTCHECKRET(ret);

    std::ofstream outpcm("out.pcm", std::ios::binary);

    while (!pcm.eof())

    {

        pcm.read(reinterpret_cast<char*>(src[0]), srcsize);

        int size = swr.convert(dst, dstlinesize, (const uint8_t**)(src), 44100, err);

        // 拷贝音频数据

        for (int i = 0; i < size; ++i) // 每个样本

        {

            for (int j = 0; j < channel; ++j) // 每个通道

            {

                outpcm.write(reinterpret_cast<const char*>(dst[j] + persize * i), persize);

            }

        }

    }

    ret = swr.unlock_opt(err);

    TESTCHECKRET(ret);

    // 清理

    if (src != nullptr)

    {

        av_freep(&src[0]);

    }

    av_freep(&src);

    if (dst != nullptr)

    {

        av_freep(&dst[0]);

    }

    av_freep(&dst);

}