FFmpeg4.0筆記：封裝ffmpeg的音頻重採樣功能類CSwr

Github

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

CSwr.h

#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:
    ~CSwr();

    // 狀態
    enum STATUS { STOP, LOCKED };
    // 設置源參數
    bool set_src_opt(int64_t layout, int rate, enum AVSampleFormat fmt, std::string& err);
    // 設置目標參數
    bool set_dst_opt(int64_t layout, int rate, enum AVSampleFormat fmt, std::string& err);
    // 鎖定設置
    bool lock_opt(std::string& err);
    // 解除鎖定
    bool unlock_opt(std::string& err);
    // 轉換
    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

#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);
    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);
    dst_layout_ = layout;
    dst_rate_ = rate;
    dst_sam_fmt_ = fmt;
    return true;
}

bool CSwr::lock_opt(std::string& err)
{
    LOCK();
    CHECKSTOP(err);
    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(swrctx_, dst_layout_, dst_sam_fmt_, dst_rate_, src_layout_, src_sam_fmt_, src_rate_, 0, nullptr) return nullptr.";
        return false;
    }
    int ret = swr_init(swrctx_);
    CHECKFFRET(ret);
    status_ = LOCKED;
    return true;
}

bool CSwr::unlock_opt(std::string& err)
{
    LOCK();
    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);
    int ret = swr_convert(swrctx_, out, out_count, in, in_count);
    CHECKFFRET(ret);
    return ret;
}

測試

#include "CDecode.h"
#include "CSws.h"
#include "CSwr.h"
#include <iostream>
#include <fstream>

CSws g_sws;
uint8_t* g_pointers[4] = { 0 };
int g_linesizes[4] = { 0 };

CSwr g_swr;
uint8_t** g_data = nullptr;
int g_linesize = 0;
int64_t g_layout = AV_CH_LAYOUT_STEREO;
int g_rate = 44100;
enum AVSampleFormat g_fmt = AV_SAMPLE_FMT_DBLP;


void DecStatusCB(CDecode::STATUS status, std::string err, void* param)
{
    std::cout << std::this_thread::get_id() << " got a status " << status << std::endl;
}

void DecFrameCB(const AVFrame* frame, CDecode::FRAMETYPE frametype, void* param)
{
    //std::cout << std::this_thread::get_id() << " got a frame." << frametype << std::endl;
    if (frametype == CDecode::FRAMETYPE::VIDEO)
    {
        if (frame->format == AV_PIX_FMT_YUV420P)
        {
            static std::ofstream video("out.rgb", std::ios::binary | std::ios::trunc);
            static int i = 0;
            if (++i > 9)
                return; 

            /*
            video.write(reinterpret_cast<const char*>(frame->data[0]), frame->linesize[0] * frame->height);
            video.write(reinterpret_cast<const char*>(frame->data[1]), frame->linesize[1] * frame->height / 2);
            video.write(reinterpret_cast<const char*>(frame->data[2]), frame->linesize[2] * frame->height / 2);
            */

            std::string err;
            // 將輸出翻轉
            g_pointers[0] += g_linesizes[0] * (240 - 1);
            g_linesizes[0] *= -1;
            // 轉換
            g_sws.scale(frame->data, frame->linesize, 0, frame->height, g_pointers, g_linesizes, err);
            // 還原指針，以便拷貝數據
            g_linesizes[0] *= -1;
            g_pointers[0] -= g_linesizes[0] * (240 - 1);
            video.write(reinterpret_cast<const char*>(g_pointers[0]), g_linesizes[0] * 240);
        }
    }
    else if (frametype == CDecode::FRAMETYPE::AUDIO)
    {
        if (frame->format == AV_SAMPLE_FMT_FLTP)
        {
            static std::ofstream audio("out.pcm", std::ios::binary | std::ios::trunc);
            std::string err;
            int ret = g_swr.convert(g_data, g_linesize, (const uint8_t * *)frame->data, frame->nb_samples, err);
            auto size = av_get_bytes_per_sample(g_fmt);
            for (int i = 0; i < ret; ++i)
            {
                for (int j = 0; j < av_get_channel_layout_nb_channels(g_layout); ++j)
                {
                    audio.write(reinterpret_cast<const char*>(g_data[j] + size * i), size);
                }
            }
        }
    }
}

int main(int argc, char* argv[])
{
    std::string err;
    bool ret = false;

    ret = g_sws.set_src_opt(AV_PIX_FMT_YUV420P, 576, 432, err);
    ret = g_sws.set_dst_opt(AV_PIX_FMT_RGB24, 320, 240, err);
    ret = g_sws.lock_opt(err);
    int size = av_image_alloc(g_pointers, g_linesizes, 320, 240, AV_PIX_FMT_RGB24, 1);

    ret = g_swr.set_src_opt(AV_CH_LAYOUT_STEREO, 48000, AV_SAMPLE_FMT_FLTP, err);
    ret = g_swr.set_dst_opt(g_layout, g_rate, g_fmt, err);
    ret = g_swr.lock_opt(err);
    size = av_samples_alloc_array_and_samples(&g_data, &g_linesize, av_get_channel_layout_nb_channels(g_layout), g_rate, g_fmt, 0);

    CDecode decode;
    ret = decode.set_input("in.flv", err);
    ret = decode.set_dec_callback(DecFrameCB, nullptr, err);
    ret = decode.set_dec_status_callback(DecStatusCB, nullptr, err);

    int i = 0;
    while (i++ < 1)
    {
        ret = decode.begindecode(err);

        std::cout << "input to stop decoding." << std::endl;
        getchar();

        ret = decode.stopdecode(err);
    }

    ret = g_sws.unlock_opt(err);
    av_freep(&g_pointers[0]);

    ret = g_swr.unlock_opt(err);
    if (g_data)
        av_freep(&g_data[0]);
    av_freep(&g_data);

    return 0;
}