ffmpeg视频解码原理和实战-（5）硬件加速解码后进行渲染并输出帧率

苦藤新鸡2024-06-13 12:32

头文件：

xvideoview.h

cpp 复制代码 
#ifndef XVIDEO_VIEW_H
#define XVIDEO_VIEW_H
#include <mutex>
#include <fstream>
struct AVFrame;

void MSleep(unsigned int ms);

//获取当前时间戳 毫秒
long long NowMs();


/// 视频渲染接口类
/// 隐藏SDL实现
/// 渲染方案可替代
// 线程安全
class XVideoView
{
public:
    enum Format  //枚举的值和ffmpeg中一致
    {
        YUV420P = 0,
        NV12 = 23,
        ARGB = 25,
        RGBA = 26,
        BGRA = 28
    };
    enum RenderType
    {
        SDL = 0
    };
    static XVideoView* Create(RenderType type = SDL);

    
    /// 初始化渲染窗口 线程安全 可多次调用
    /// @para w 窗口宽度
    /// @para h 窗口高度
    /// @para fmt 绘制的像素格式
    /// @para win_id 窗口句柄，如果为空，创建新窗口
    /// @return 是否创建成功
    virtual bool Init(int w, int h,
        Format fmt = RGBA) = 0;

    //清理所有申请的资源，包括关闭窗口
    virtual void Close() = 0;

    //处理窗口退出事件
    virtual bool IsExit() = 0;

    //
    /// 渲染图像 线程安全
    ///@para data 渲染的二进制数据
    ///@para linesize 一行数据的字节数，对于YUV420P就是Y一行字节数
    /// linesize<=0 就根据宽度和像素格式自动算出大小
    /// @return 渲染是否成功
    virtual bool Draw(const unsigned  char* data, int linesize = 0) = 0;
    virtual bool Draw(
        const unsigned  char* y, int y_pitch,
        const unsigned  char* u, int u_pitch,
        const unsigned  char* v, int v_pitch
    ) = 0;


    //显示缩放
    void Scale(int w, int h)
    {
        scale_w_ = w;
        scale_h_ = h;
    }

    bool DrawFrame(AVFrame* frame);

    int render_fps() { return render_fps_; }

    //打开文件
    bool Open(std::string filepath);


    //
    /// 读取一帧数据，并维护AVFrame空间
    /// 每次调用会覆盖上一次数据
    AVFrame* Read();
    void set_win_id(void* win) { win_id_ = win; }
    virtual ~XVideoView();
protected:
    void* win_id_ = nullptr; //窗口句柄
    int render_fps_ = 0;       //显示帧率
    int width_ = 0;             //材质宽高
    int height_ = 0;
    Format fmt_ = RGBA;         //像素格式
    std::mutex mtx_;            //确保线程安全
    int scale_w_ = 0;           //显示大小
    int scale_h_ = 0;
    long long beg_ms_ = 0;       //计时开始时间
    int count_ = 0;              //统计显示次数
    unsigned char* cache_ = nullptr;//用于复制NV12缓冲
private:
    std::ifstream ifs_;
    AVFrame* frame_ = nullptr;
};

#endif

xsdl.h

cpp 复制代码 
#pragma once


#include "xvideoview.h"
struct SDL_Window;
struct SDL_Renderer;
struct SDL_Texture;
class XSDL :public XVideoView
{
public:
    void Close() override;
    
    /// 初始化渲染窗口 线程安全
    /// @para w 窗口宽度
    /// @para h 窗口高度
    /// @para fmt 绘制的像素格式
    /// @para win_id 窗口句柄，如果为空，创建新窗口
    /// @return 是否创建成功
    bool Init(int w, int h,
        Format fmt = RGBA) override;

    //
    /// 渲染图像 线程安全
    ///@para data 渲染的二进制数据
    ///@para linesize 一行数据的字节数，对于YUV420P就是Y一行字节数
    /// linesize<=0 就根据宽度和像素格式自动算出大小
    /// @return 渲染是否成功
    bool Draw(const unsigned  char* data,
        int linesize = 0) override;
    bool Draw(
        const unsigned  char* y, int y_pitch,
        const unsigned  char* u, int u_pitch,
        const unsigned  char* v, int v_pitch
    ) override;
    bool IsExit() override;
private:
    SDL_Window* win_ = nullptr;
    SDL_Renderer* render_ = nullptr;
    SDL_Texture* texture_ = nullptr;
};

源文件：

xvideoview.cpp

cpp 复制代码 
#include "xsdl.h"
#include <thread>
#include <iostream>
using namespace std;
extern "C"
{
#include <libavcodec/avcodec.h>
}
#pragma comment(lib,"avutil.lib")

void MSleep(unsigned int ms)
{
	auto beg = clock();
	for (int i = 0; i < ms; i++)
	{
		this_thread::sleep_for(1ms);
		if ((clock() - beg) / (CLOCKS_PER_SEC / 1000) >= ms)
			break;
	}
}
long long NowMs()
{
	return clock() / (CLOCKS_PER_SEC / 1000);
}
AVFrame* XVideoView::Read()
{
	if (width_ <= 0 || height_ <= 0 || !ifs_)return NULL;
	//AVFrame空间已经申请，如果参数发生变化，需要释放空间
	if (frame_)
	{
		if (frame_->width != width_
			|| frame_->height != height_
			|| frame_->format != fmt_)
		{
			//释放AVFrame对象空间，和buf引用计数减一
			av_frame_free(&frame_);
		}
	}
	if (!frame_)
	{
		//分配对象空间和像素空间
		frame_ = av_frame_alloc();
		frame_->width = width_;
		frame_->height = height_;
		frame_->format = fmt_;
		frame_->linesize[0] = width_ * 4;
		if (frame_->format == AV_PIX_FMT_YUV420P)
		{
			frame_->linesize[0] = width_; // Y
			frame_->linesize[1] = width_ / 2;//U
			frame_->linesize[2] = width_ / 2;//V
		}

		//生成AVFrame空间，使用默认对齐
		auto re = av_frame_get_buffer(frame_, 0);
		if (re != 0)
		{
			char buf[1024] = { 0 };
			av_strerror(re, buf, sizeof(buf) - 1);
			cout << buf << endl;
			av_frame_free(&frame_);
			return NULL;

		}
	}
	if (!frame_)return NULL;

	//读取一帧数据
	if (frame_->format == AV_PIX_FMT_YUV420P)
	{
		ifs_.read((char*)frame_->data[0],
			frame_->linesize[0] * height_);	//Y
		ifs_.read((char*)frame_->data[1],
			frame_->linesize[1] * height_ / 2);	//U
		ifs_.read((char*)frame_->data[2],
			frame_->linesize[2] * height_ / 2);	//V
	}
	else	//RGBA ARGB BGRA 32
	{
		ifs_.read((char*)frame_->data[0], frame_->linesize[0] * height_);
	}

	if (ifs_.gcount() == 0)
		return NULL;
	return frame_;




}

//打开文件
bool XVideoView::Open(std::string filepath)
{
	if (ifs_.is_open())
	{
		ifs_.close();
	}
	ifs_.open(filepath, ios::binary);
	return ifs_.is_open();
}
XVideoView* XVideoView::Create(RenderType type)
{
	switch (type)
	{
	case XVideoView::SDL:
		return new XSDL();
		break;
	default:
		break;
	}
	return nullptr;
}
XVideoView::~XVideoView()
{
	if (cache_)
		delete cache_;
	cache_ = nullptr;
}

bool XVideoView::DrawFrame(AVFrame* frame)
{
	if (!frame || !frame->data[0])return false;
	count_++;
	if (beg_ms_ <= 0)
	{
		beg_ms_ = clock();
	}
	//计算显示帧率
	else if ((clock() - beg_ms_) / (CLOCKS_PER_SEC / 1000) >= 1000) //一秒计算一次fps
	{
		render_fps_ = count_;
		count_ = 0;
		beg_ms_ = clock();
	}
	int linesize = 0;
	switch (frame->format)
	{
	case AV_PIX_FMT_YUV420P:
		return Draw(frame->data[0], frame->linesize[0],//Y
			frame->data[1], frame->linesize[1],	//U
			frame->data[2], frame->linesize[2]	//V
		);
	case AV_PIX_FMT_NV12:
		if (!cache_)
		{
			cache_ = new unsigned char[4096 * 2160 * 1.5];
		}
		linesize = frame->width;
		if (frame->linesize[0] == frame->width)
		{
			memcpy(cache_, frame->data[0], frame->linesize[0] * frame->height); //Y
			memcpy(cache_ + frame->linesize[0] * frame->height, frame->data[1], frame->linesize[1] * frame->height / 2); //UV
		}
		else //逐行复制
		{
			for (int i = 0; i < frame->height; i++) //Y
			{
				memcpy(cache_ + i * frame->width,
					frame->data[0] + i * frame->linesize[0],
					frame->width
				);
			}
			for (int i = 0; i < frame->height / 2; i++)  //UV
			{
				auto p = cache_ + frame->height * frame->width;// 移位Y
				memcpy(p + i * frame->width,
					frame->data[1] + i * frame->linesize[1],
					frame->width
				);
			}
		}

		//frame->data[0] + frame->data[1]
		return Draw(cache_, linesize);
	case AV_PIX_FMT_BGRA:
	case AV_PIX_FMT_ARGB:
	case AV_PIX_FMT_RGBA:
		return Draw(frame->data[0], frame->linesize[0]);
	default:
		break;
	}
	return false;
}

xsdl.cpp

cpp 复制代码 
#include "xsdl.h"
#include "sdl/SDL.h"
#include <iostream>
using namespace std;
#pragma comment(lib,"SDL2.lib")
static bool InitVideo()
{
    static bool is_first = true;
    static mutex mux;
    unique_lock<mutex> sdl_lock(mux);
    if (!is_first)return true;
    is_first = false;
    if (SDL_Init(SDL_INIT_VIDEO))
    {
        cout << SDL_GetError() << endl;
        return false;
    }
    //设定缩放算法，解决锯齿问题,线性插值算法
    SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "1");
    return true;
}
bool XSDL::IsExit()
{
    SDL_Event ev;
    SDL_WaitEventTimeout(&ev, 1);
    if (ev.type == SDL_QUIT)
        return true;
    return false;
}
void XSDL::Close()
{
    //确保线程安全
    unique_lock<mutex> sdl_lock(mtx_);
    if (texture_)
    {
        SDL_DestroyTexture(texture_);
        texture_ = nullptr;
    }
    if (render_)
    {
        SDL_DestroyRenderer(render_);
        render_ = nullptr;
    }
    if (win_)
    {
        SDL_DestroyWindow(win_);
        win_ = nullptr;
    }
}

bool XSDL::Init(int w, int h, Format fmt)
{
    if (w <= 0 || h <= 0)return false;
    //初始化SDL 视频库
    InitVideo();

    //确保线程安全
    unique_lock<mutex> sdl_lock(mtx_);
    width_ = w;
    height_ = h;
    fmt_ = fmt;

    if (texture_)
        SDL_DestroyTexture(texture_);
    if (render_)
        SDL_DestroyRenderer(render_);

    ///1 创建窗口
    if (!win_)
    {
        if (!win_id_)
        {
            //新建窗口
            win_ = SDL_CreateWindow("",
                SDL_WINDOWPOS_UNDEFINED,
                SDL_WINDOWPOS_UNDEFINED,
                w, h, SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE
            );
        }
        else
        {
            //渲染到控件窗口
            win_ = SDL_CreateWindowFrom(win_id_);
        }
    }
    if (!win_)
    {
        cerr << SDL_GetError() << endl;
        return false;
    }

    /// 2 创建渲染器

    render_ = SDL_CreateRenderer(win_, -1, SDL_RENDERER_ACCELERATED);
    if (!render_)
    {
        cerr << SDL_GetError() << endl;
        return false;
    }
    //创建材质 （显存）
    unsigned int sdl_fmt = SDL_PIXELFORMAT_RGBA8888;
    switch (fmt)
    {
    case XVideoView::RGBA:
        sdl_fmt = SDL_PIXELFORMAT_RGBA32;
        break;
    case XVideoView::BGRA:
        sdl_fmt = SDL_PIXELFORMAT_BGRA32;
        break;
    case XVideoView::ARGB:
        sdl_fmt = SDL_PIXELFORMAT_ARGB32;
        break;
    case XVideoView::YUV420P:
        sdl_fmt = SDL_PIXELFORMAT_IYUV;
        break;
    case XVideoView::NV12:
        sdl_fmt = SDL_PIXELFORMAT_NV12;
        break;
    default:
        break;
    }

    texture_ = SDL_CreateTexture(render_,
        sdl_fmt,                        //像素格式
        SDL_TEXTUREACCESS_STREAMING,    //频繁修改的渲染（带锁）
        w, h                            //材质大小
    );
    if (!texture_)
    {
        cerr << SDL_GetError() << endl;
        return false;
    }
    return true;
}
bool XSDL::Draw(
    const unsigned  char* y, int y_pitch,
    const unsigned  char* u, int u_pitch,
    const unsigned  char* v, int v_pitch
)
{
    //参数检查
    if (!y || !u || !v)return false;
    unique_lock<mutex> sdl_lock(mtx_);
    if (!texture_ || !render_ || !win_ || width_ <= 0 || height_ <= 0)
        return false;

    //复制内存到显显存
    auto re = SDL_UpdateYUVTexture(texture_,
        NULL,
        y, y_pitch,
        u, u_pitch,
        v, v_pitch);
    if (re != 0)
    {
        cout << SDL_GetError() << endl;
        return false;
    }
    //清空屏幕
    SDL_RenderClear(render_);

    //材质复制到渲染器

    SDL_Rect rect;
    SDL_Rect* prect = nullptr;
    if (scale_w_ > 0)  //用户手动设置缩放
    {
        rect.x = 0; rect.y = 0;
        rect.w = scale_w_;//渲染的宽高，可缩放
        rect.h = scale_w_;
        prect = &rect;
    }
    re = SDL_RenderCopy(render_, texture_, NULL, prect);
    if (re != 0)
    {
        cout << SDL_GetError() << endl;
        return false;
    }
    SDL_RenderPresent(render_);
    return true;
}
bool XSDL::Draw(const unsigned char* data, int linesize)
{
    if (!data)return false;
    unique_lock<mutex> sdl_lock(mtx_);
    if (!texture_ || !render_ || !win_ || width_ <= 0 || height_ <= 0)
        return false;
    if (linesize <= 0)
    {
        switch (fmt_)
        {
        case XVideoView::RGBA:
        case XVideoView::ARGB:
            linesize = width_ * 4;
            break;
        case XVideoView::YUV420P:
            linesize = width_;
            break;
        default:
            break;
        }
    }
    if (linesize <= 0)
        return false;
    //复制内存到显显存
    auto re = SDL_UpdateTexture(texture_, NULL, data, linesize);
    if (re != 0)
    {
        cout << SDL_GetError() << endl;
        return false;
    }
    //清空屏幕
    SDL_RenderClear(render_);

    //材质复制到渲染器

    SDL_Rect rect;
    SDL_Rect* prect = nullptr;
    if (scale_w_ > 0)  //用户手动设置缩放
    {
        rect.x = 0; rect.y = 0;
        rect.w = scale_w_;//渲染的宽高，可缩放
        rect.h = scale_w_;
        prect = &rect;
    }
    re = SDL_RenderCopy(render_, texture_, NULL, prect);
    if (re != 0)
    {
        cout << SDL_GetError() << endl;
        return false;
    }
    SDL_RenderPresent(render_);
    return true;
}

main.cpp

cpp 复制代码 
#include <iostream>
#include <fstream>
#include<string>
#include"xsdl.h"
using namespace std;
extern "C" { //指定函数是c语言函数，函数名不包含重载标注
//引用ffmpeg头文件
#include <libavcodec/avcodec.h>
#include <libavutil/opt.h>
}
//预处理指令导入库
#pragma comment(lib,"avcodec.lib")
#pragma comment(lib,"avutil.lib")
int main(int argc, char* argv[])
{
    auto view = XVideoView::Create();
    //1 分割h264 存入AVPacket
      // ffmpeg -i v1080.mp4 -s 400x300 test.h264
    string filename = "test.h264";
    ifstream ifs(filename, ios::binary);
    if (!ifs)return -1;
    unsigned char inbuf[4096] = { 0 };//用于存储h264编码流

    AVCodecID codec_id = AV_CODEC_ID_H264;

    //1 找解码器
    auto codec = avcodec_find_decoder(codec_id);

    //2 创建解码器上下文
    AVCodecContext *c = avcodec_alloc_context3(codec);


    //硬件加速格式 DXVA2
    AVHWDeviceType hw_type = AV_HWDEVICE_TYPE_DXVA2;
    
    /// 打印所有支持的硬件加速方式
    for (int i = 0;; i++)
    {
        //const AVCodecHWConfig *avcodec_get_hw_config(const AVCodec *codec, int index);
        //用于获取指定编解码器的硬件加速配置。
        //index: 硬件配置的索引值，从 0 开始递增。用于遍历所有可用的硬件配置。
        const AVCodecHWConfig *config = avcodec_get_hw_config(codec, i);
        if (!config)break;
        if (config->device_type)
            //const char *av_hwdevice_get_type_name(enum AVHWDeviceType type);
            //该函数接收一个 AVHWDeviceType 类型的参数，并返回一个描述该硬件设备类型的字符串指针
            //如 CUDA、DXVA2、VAAPI 等。
            cout << av_hwdevice_get_type_name(config->device_type) << endl;
    }

    //初始化硬件加速器上下文 
    AVBufferRef* hw_ctx = nullptr;
    av_hwdevice_ctx_create(&hw_ctx, hw_type, NULL, NULL, 0);

    //设定硬件GPU加速
    c->hw_device_ctx = av_buffer_ref(hw_ctx);//把硬件加速器上下文引用赋值给解码器上下文，以便在后续的编码或解码操作中利用硬件加速功能
    c->thread_count = 16;
   
    //3 打开编码器上下文
    avcodec_open2(c, NULL, NULL);

    //分割上下文
    AVCodecParserContext* parser = av_parser_init(codec_id);
    AVPacket* pkt = av_packet_alloc();
    AVFrame* frame = av_frame_alloc();
    AVFrame* hw_frame = av_frame_alloc(); //硬解码转换用这个frame
    long long begin = NowMs();
    int count = 0;//解码统计
    bool is_init_win = false;

    while (!ifs.eof())
    {
        ifs.read((char*)inbuf, sizeof(inbuf));//将h264编码的流读入inbuf中，一次读4096
        int data_size = ifs.gcount();// 返回上一次读取操作实际读取的字符数,并用data_size记录
        if (data_size <= 0)break;

        //检查输入流是否已经到达文件末尾（EOF，End Of File）
        if (ifs.eof())
        {
            ifs.clear();
            ifs.seekg(0, ios::beg);//回到文件开头重复读取
        }
        auto data = inbuf;//data和inbuf指向同一片区域
        while (data_size > 0) //一次有多帧数据
        {
         
            //通过0001 截断输出到AVPacket 返回帧大小
            int ret = av_parser_parse2(parser, c,
                &pkt->data, &pkt->size, //截断后输出到AVpacket的data中
                data, data_size,        //h264编码流，待处理数据
                AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0
            );//返回消耗的输入数据字节数ret。如果所有输入数据都被消耗，则返回值等于 buf_size。如果解析过程中出现错误，则返回负数。
            data += ret;//data指针向前移动 ret个字节,继续处理inbuf未处理的数据
            data_size -= ret; //待处理的数据大小
            if (pkt->size)//如果还有截断后的avpacket流则进行解码操作
            {
                //cout << pkt->size << " "<<flush;
                //发送packet到解码线程
                ret = avcodec_send_packet(c, pkt);//把avpacket给解码器进行解码
                if (ret < 0)
                    break;
                //获取多帧解码数据 
               
                while (ret >= 0)//如果解码成功
                {
                    //每次回调用av_frame_unref 
                    ret = avcodec_receive_frame(c, frame);//拿到解码后的数据存储到frame中
                    if (ret < 0)
                        break;
                    auto pframe = frame;  //为了同时支持硬解码和软解码
                    if (c->hw_device_ctx) //硬解码
                    {
                        //硬解码转换GPU =》CPU ，显存=》内存
                        //AV_PIX_FMT_NV12,      ///< planar YUV 4:2:0, 12bpp, 1 plane for Y and 1 plane for the UV components, which are interleaved (first byte U and the following byte V)
                        av_hwframe_transfer_data(hw_frame, frame, 0);
                        pframe = hw_frame;//如果是硬解码则pframe = hw_frame

                    }
                    //AV_PIX_FMT_DXVA2_VLD
                    AV_PIX_FMT_DXVA2_VLD;
                    cout << frame->format << " " << flush;
                    //
                 /// 第一帧初始化窗口
                    if (!is_init_win)
                    {
                        is_init_win = true;
                        view->Init(pframe->width, pframe->height, (XVideoView::Format)pframe->format);
                    }
                    view->DrawFrame(pframe);

                    count++;
                    auto cur = NowMs();
                    if (cur - begin >= 1000)// 1秒钟计算一次
                    {
                        cout << "\nfps = " << count << endl;
                        count = 0;
                        begin = cur;
                    }
                }
            }
        }
    }
    ///取出缓存数据,防止丢帧
    int ret = avcodec_send_packet(c, NULL);
    while (ret >= 0)
    {
        ret = avcodec_receive_frame(c, frame);
        if (ret < 0)
            break;
        cout << frame->format << "-" << flush;
    }
    av_parser_close(parser);
    avcodec_free_context(&c);
    av_frame_free(&frame);
    av_packet_free(&pkt);

    getchar();
    return 0;
}

运行结果：

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