C++使用ffmpeg + SDL2.0搭建简单播放器
c++ ffmpeg 播放器 SDL   发布于 2019-01-31   714人围观  0条评论
c++ ffmpeg 播放器 SDL   发表于 2019-01-31   714人围观  0条评论

前言

本文参考雷霄骅的博文https://blog.csdn.net/leixiaohua1020/article/details/8652605,使用c++根据ffmpeg-4.1版本改写(原文代码基于旧版本ffmpeg)。代码见下文。

本文代码地址见https://github.com/2997215859/ffplay-learn/blob/master/Video/print_info.cpp

本文代码基于ffmpeg-4.1版本,事先需要安装好ffmpeg

本文代码提供CMakeLists.txt,见附录CMakeLists.txt部分,或根据CMakeLists.txt改写。需要链接的库如下(基本上安装ffmpeg、ffplay、SDL2之后就有了)。

 1   avdevice avfilter avformat avcodec swscale swresample postproc avutil m xcb xcb-shm xcb xcb-shape xcb xcb-xfixes xcb-render xcb-shape xcb asound pthread m fontconfig freetype freetype z bz2 lzma SDL2 SDL2main

 流程

 

解码器即C++中使用ffmpeg解码视频到YUV数据示例,SDL渲染是一个封装了音视频底层接口的库,本文使用2.0版本。

解码器主要使用ffmpeg中的几个函数:avformat_alloc_context, avcodec_find_decoder, avcodec_send_packet​, avcodec_receive_frame

代码剖析

读取视频格式并获取视频流的索引

    string filepath = "/home/sensetime/videos/big_buck_bunny_720p_30mb.mp4";

    avdevice_register_all();
    avformat_network_init();

    AVFormatContext *avFormatContext = avformat_alloc_context();
    if (avformat_open_input(&avFormatContext, filepath.c_str(), NULL, NULL) != 0) { // 打开输入流
        cerr << "Failed to open input stream" << endl;
        exit(1);
    }

    if (avformat_find_stream_info(avFormatContext, NULL) < 0) { // 分析流信息
        cerr << "Failed to find stream information." << endl;
        exit(1);
    }


    int videoIndex = -1;
    for (int i=0;i<avFormatContext->nb_streams;i++) { // 查找第一个视频流的索引
        if (avFormatContext->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoIndex = i;
            break;
        }
    }

    if (videoIndex == -1) {
        cerr << "Failed to find a video stream." << endl;
        exit(1);
    }

构造解码器和解码上下文

    AVStream *avStream = avFormatContext->streams[videoIndex];
    AVCodec *avCodec = avcodec_find_decoder(avStream->codecpar->codec_id);

    AVCodecContext *avCodecContext = avcodec_alloc_context3(avCodec); // 为该解码器新建解码上下文
    if (!avCodecContext) {
        cerr << "Failed to allocate the decoder context for stream" << endl;
        return -1;
    }
    if(avcodec_parameters_to_context(avCodecContext, avStream->codecpar) < 0) { // 将流的解码参数拷贝到解码上下文
        cerr << "Failed to copy decoder parameters to input decoder context." << endl;
        return -1;
    }

    avCodecContext->pkt_timebase = avStream->time_base;
    cout << avCodec->id << endl;

    if (avcodec_open2(avCodecContext, avCodec, NULL) < 0) {
        cerr << "Failed to open codec." << endl;
        exit(1);
    }

解码

解码使用avcodec_send_packet​, avcodec_receive_frame这一对函数解码,代码结构如下

    
    ... 
    // yuvFrame用于存储新帧,这段代码是为其分配存储空间
    AVFrame *yuvFrame = av_frame_alloc();
    int bufferSize = av_image_get_buffer_size(AV_PIX_FMT_YUV420P, avCodecContext->width, avCodecContext->height, 1);
    unsigned char *buffer = (unsigned char*)av_malloc(bufferSize);
    av_image_fill_arrays(yuvFrame->data, yuvFrame->linesize, buffer, AV_PIX_FMT_YUV420P, avCodecContext->width, avCodecContext->height, 1);
    ...
    ... 
    // swsContext是用于转换帧格式(比如长宽、像素存储方式等)的上下文类型,frame将由此上下文转换到yuvFrame上,再由SDL渲染到显示器
    SwsContext *imgConvertContext = sws_getContext(avCodecContext->width, avCodecContext->height, avCodecContext->pix_fmt,
        avCodecContext->width, avCodecContext->height, AV_PIX_FMT_YUV420P,
        SWS_BICUBIC, NULL, NULL, NULL);
    ...
    
    
    while (av_read_frame(avFormatContext, avPacket) >= 0) { // 从format上下文中读取压缩编码的数据包packet
        if (avPacket->stream_index == videoIndex) { // 只处理视频类型的packet,音频类型的packet
            if (avcodec_send_packet(avCodecContext, avPacket) < 0) { // 将packet提交到解码上下文
                cerr << "Failed to submitting the packet to the decoder\n";
                return -1;
            }
            int ret;
            while (true) {
                SDL_WaitEvent(&event); // 阻塞等待事件

                if (event.type == SFM_REFRESH_EVENT) {
                    if (avcodec_receive_frame(avCodecContext, frame) >= 0) { // 从解码上下文中读取帧frame

                        // 使用sws_scale函数转换帧frame的格式,填写到新的帧yumFrame
                        sws_scale(imgConvertContext, frame->data, frame->linesize, 0, avCodecContext->height, yuvFrame->data, yuvFrame->linesize);
                        yuvFrame->height = frame->height;
                        yuvFrame->width = frame->width;

                        ...
                        // 中间这块可以对yuvFrame做其他处理,比如画文字、画框
                        ...
                         
                        // 使用SDL渲染yuvFrame
                        ...
                        
                    } else {
                        break; 
                    }

                } else if(event.type==SDL_KEYDOWN){
                    //Pause
                    if(event.key.keysym.sym==SDLK_SPACE)
                        stopRefresh =! stopRefresh;
                }else if(event.type==SDL_QUIT){
                    stopThread = 1;
                }else if(event.type==SFM_BREAK_EVENT){
                    break;
                }
            }
        }
        av_packet_unref(avPacket);
    }

SDL渲染

SDL 渲染前,需要建立渲染窗口和纹理

    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
        cerr << "Failed to initialization SDL - " <<  SDL_GetError();
        exit(1);
    }

    int screenW = avCodecContext->width;
    int screenH = avCodecContext->height;
    SDL_Window *screen = SDL_CreateWindow("simple ffmpeg player's window", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
                                          screenW, screenH, SDL_WINDOW_OPENGL);

    if (!screen) {
        cerr << "SDL: could not create window - " << SDL_GetError();
        exit(1);
    }

    SDL_Renderer *sdlRenderer = SDL_CreateRenderer(screen, -1, 0);

    SDL_Texture *sdlTexture = SDL_CreateTexture(sdlRenderer, SDL_PIXELFORMAT_IYUV, SDL_TEXTUREACCESS_STREAMING, avCodecContext->width, avCodecContext->height);

    SDL_Rect sdlRect;
    sdlRect.x = 0;
    sdlRect.y = 0;
    sdlRect.w = screenW;
    sdlRect.h = screenH;

SDL渲染帧

                        SDL_UpdateTexture(sdlTexture, NULL, yuvFrame->data[0], yuvFrame->linesize[0]);
                        SDL_RenderClear(sdlRenderer);
                        SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, NULL);
                        SDL_RenderPresent(sdlRenderer);

刷新线程

刷新线程使用SDL_CreateThread创建

SDL_CreateThread(refreshThread, NULL, NULL);​
int refreshThread (void *opaque) {
    stopThread = false;
    SDL_Event event;
    event.type = SFM_REFRESH_EVENT;
    while (!stopThread) {
        if (!stopRefresh) {
            SDL_PushEvent(&event);
        }
        SDL_Delay(40); // 40ms 刷新一次SDL
    }
    stopThread = false;
    stopRefresh = false;

    {
        SDL_Event event;
        event.type = SFM_BREAK_EVENT;
        SDL_PushEvent(&event);
    }

    return 0;
}

 

附录

完整代码

#include <atomic>
#include <string>
#include <iostream>

#ifdef __cplusplus
extern "C" {
#endif

#include <libavutil/avutil.h>
#include <libavdevice/avdevice.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <libavutil/imgutils.h>
#include <SDL2/SDL.h>
#include <libavutil/parseutils.h>
#include <libavutil/bprint.h>
#include <libavutil/tree.h>
#include <libavutil/eval.h>
#include <libavutil/lfg.h>
#include <libavutil/timecode.h>
#include <libavutil/file.h>
#include <libavutil/random_seed.h>
#include <fenv.h>

#ifdef __cplusplus
}
#endif

#define SFM_REFRESH_EVENT (SDL_USEREVENT + 1)
#define SFM_BREAK_EVENT (SDL_USEREVENT + 2)

using namespace std;

atomic<bool> stopThread(false);
atomic<bool> stopRefresh(false);

int refreshThread (void *opaque) {
    stopThread = false;
    SDL_Event event;
    event.type = SFM_REFRESH_EVENT;
    while (!stopThread) {
        if (!stopRefresh) {
            SDL_PushEvent(&event);
        }
        SDL_Delay(40); // 40ms 刷新一次SDL
    }
    stopThread = false;
    stopRefresh = false;

    {
        SDL_Event event;
        event.type = SFM_BREAK_EVENT;
        SDL_PushEvent(&event);
    }

    return 0;
}

int main () {
    string filepath = "/home/sensetime/videos/big_buck_bunny_720p_30mb.mp4";

    avdevice_register_all();
    avformat_network_init();

    AVFormatContext *avFormatContext = avformat_alloc_context();
    if (avformat_open_input(&avFormatContext, filepath.c_str(), NULL, NULL) != 0) { // 打开输入流
        cerr << "Failed to open input stream" << endl;
        exit(1);
    }

    if (avformat_find_stream_info(avFormatContext, NULL) < 0) { // 分析流信息
        cerr << "Failed to find stream information." << endl;
        exit(1);
    }


    int videoIndex = -1;
    for (int i=0;i<avFormatContext->nb_streams;i++) { // 查找第一个视频流的索引
        if (avFormatContext->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoIndex = i;
            break;
        }
    }

    if (videoIndex == -1) {
        cerr << "Failed to find a video stream." << endl;
        exit(1);
    }

    AVStream *avStream = avFormatContext->streams[videoIndex];
    AVCodec *avCodec = avcodec_find_decoder(avStream->codecpar->codec_id);

    AVCodecContext *avCodecContext = avcodec_alloc_context3(avCodec); // 为该解码器新建解码上下文
    if (!avCodecContext) {
        cerr << "Failed to allocate the decoder context for stream" << endl;
        return -1;
    }
    if(avcodec_parameters_to_context(avCodecContext, avStream->codecpar) < 0) { // 将流的解码参数拷贝到解码上下文
        cerr << "Failed to copy decoder parameters to input decoder context." << endl;
        return -1;
    }

    avCodecContext->pkt_timebase = avStream->time_base;
    cout << avCodec->id << endl;

    if (avcodec_open2(avCodecContext, avCodec, NULL) < 0) {
        cerr << "Failed to open codec." << endl;
        exit(1);
    }

    // yuvFrame用于存储新帧,这段代码是为其分配存储空间
    AVFrame *yuvFrame = av_frame_alloc();
    int bufferSize = av_image_get_buffer_size(AV_PIX_FMT_YUV420P, avCodecContext->width, avCodecContext->height, 1);
    unsigned char *buffer = (unsigned char*)av_malloc(bufferSize);
    av_image_fill_arrays(yuvFrame->data, yuvFrame->linesize, buffer, AV_PIX_FMT_YUV420P, avCodecContext->width, avCodecContext->height, 1);

    //Output Info-----------------------------
    printf("---------------- File Information ---------------\n");
    av_dump_format(avFormatContext, 0, filepath.c_str(),0);
    printf("-------------------------------------------------\n");

    SwsContext *imgConvertContext = sws_getContext(avCodecContext->width, avCodecContext->height, avCodecContext->pix_fmt,
            avCodecContext->width, avCodecContext->height, AV_PIX_FMT_YUV420P,
            SWS_BICUBIC, NULL, NULL, NULL);

    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
        cerr << "Failed to initialization SDL - " <<  SDL_GetError();
        exit(1);
    }

    int screenW = avCodecContext->width;
    int screenH = avCodecContext->height;
    SDL_Window *screen = SDL_CreateWindow("simple ffmpeg player's window", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
                                          screenW, screenH, SDL_WINDOW_OPENGL);

    if (!screen) {
        cerr << "SDL: could not create window - " << SDL_GetError();
        exit(1);
    }

    SDL_Renderer *sdlRenderer = SDL_CreateRenderer(screen, -1, 0);

    SDL_Texture *sdlTexture = SDL_CreateTexture(sdlRenderer, SDL_PIXELFORMAT_IYUV, SDL_TEXTUREACCESS_STREAMING, avCodecContext->width, avCodecContext->height);

    SDL_Rect sdlRect;
    sdlRect.x = 0;
    sdlRect.y = 0;
    sdlRect.w = screenW;
    sdlRect.h = screenH;

    SDL_CreateThread(refreshThread, NULL, NULL);

    SDL_Event event;
    AVPacket *avPacket = (AVPacket*) av_malloc(sizeof(AVPacket));
    AVFrame *frame = av_frame_alloc();

    double timeBase = av_q2d(avStream->time_base);
    double frameRate = av_q2d(avStream->avg_frame_rate);
    double interval = 1 / (timeBase * frameRate);

    while (av_read_frame(avFormatContext, avPacket) >= 0) { // 从format上下文中读取压缩编码的数据包
        if (avPacket->stream_index == videoIndex) { // 只处理视频类型的packet,音频类型的packet
            if (avcodec_send_packet(avCodecContext, avPacket) < 0) { // 将packet提交到解码上下文
                cerr << "Failed to submitting the packet to the decoder\n";
                return -1;
            }
            int ret;
            while (true) {
                SDL_WaitEvent(&event);// 阻塞等待事件

                if (event.type == SFM_REFRESH_EVENT) {
                    if (avcodec_receive_frame(avCodecContext, frame) >= 0) { // 从解码上下文中读取帧frame

                        sws_scale(imgConvertContext, frame->data, frame->linesize, 0, avCodecContext->height, yuvFrame->data, yuvFrame->linesize);
                        yuvFrame->height = frame->height;
                        yuvFrame->width = frame->width;

                        SDL_UpdateTexture(sdlTexture, NULL, yuvFrame->data[0], yuvFrame->linesize[0]);
                        SDL_RenderClear(sdlRenderer);
                        SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, NULL);
                        SDL_RenderPresent(sdlRenderer);
                        av_frame_unref(frame);
                    } else {
                        break; 
                    }

                } else if(event.type==SDL_KEYDOWN){
                    //Pause
                    if(event.key.keysym.sym==SDLK_SPACE)
                        stopRefresh =! stopRefresh;
                }else if(event.type==SDL_QUIT){
                    stopThread = 1;
                }else if(event.type==SFM_BREAK_EVENT){
                    break;
                }
            }
        }
        av_packet_unref(avPacket);
    }

    sws_freeContext(imgConvertContext);

    SDL_Quit();
    av_frame_unref(frame);
    av_frame_unref(yuvFrame);
    avcodec_close(avCodecContext);
    avformat_close_input(&avFormatContext);
    return 0;
}

 CMakeLists.txt

cmake_minimum_required(VERSION 3.13)
project(player)

set(CMAKE_CXX_STANDARD 11)

include_directories(./)
include_directories(/usr/include/.)
include_directories(/usr/local/include/.)

link_directories(/usr/lib/)
link_directories(/usr/local/lib/)

# 设置可执行文件生成路径
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/bin")


# 生成debug版本
SET(CMAKE_BUILD_TYPE "release")
if (CMAKE_BUILD_TYPE STREQUAL debug)
    add_definitions(-D_DEBUG)
endif ()
SET(CMAKE_CXX_FLAGS_DEBUG "$ENV{CXXFLAGS} -O0 -Wall -g -ggdb -std=c++11")
SET(CMAKE_CXX_FLAGS_RELEASE "$ENV{CXXFLAGS} -O3 -Wall -std=c++11")

link_directories(/usr/include/freetype2/.)
add_executable(simple_player
        simple_player.cpp)
target_link_libraries(simple_player
        avdevice
        avfilter
        avformat
        avcodec
        swscale
        swresample
        postproc
        avutil
        #        avresample
        m xcb xcb-shm xcb xcb-shape xcb xcb-xfixes xcb-render xcb-shape xcb asound
        pthread m fontconfig freetype freetype
        z
        bz2
        lzma
        SDL2
        SDL2main)

 

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