基于 FFMPEG + SDL2 的视频播放器

缺乏、安全感 2021-09-25 12:18 593阅读 0赞

# 基于 FFMPEG + SDL2 的视频播放器 #

本文是在雷神的 [最简单的基于FFMPEG+SDL的视频播放器 ver2 （采用SDL2.0）][FFMPEG_SDL_ ver2 _SDL2.0] 的基础上修改的，对雷神代码中 ffmpeg 弃用的函数做了修改。与雷神博客一样同样实现了普通版本和 su 版本。

SU 版特征如下：

*  SDL弹出的窗口可以移动了
 *  画面显示是严格的40ms一帧

所有代码均在 VS2017 C++17，SDL-2.0.14 版本上测试通过。

## FFMPEG 解码流程 ##

![在这里插入图片描述][44ed29faa89d3569d052d2100026569c.png]

## VideoPlayer 类声明 ##

#pragma once
    #ifdef __cplusplus
    extern "C" { 
    #endif
    
    #include "libavcodec/avcodec.h"
    #include "libavformat/avformat.h"
    #include "libswscale/swscale.h"
    #include "libavutil/imgutils.h"
    #include "SDL.h"
    
    #ifdef __cplusplus
    }
    #endif
    
    #include <iostream>
    
    class VideoPlayer { 
    public:
    	VideoPlayer(const std::string& file_path);
    	~VideoPlayer();
    
    	// call this function before use VideoPlayer.
    	bool InitVideoPlayer();
    
    	void Show();
    
    private:	
    	AVFormatContext* fmt_ctx_{  nullptr };
    	AVCodecContext* codec_ctx_{  nullptr };
    	AVCodec* codec_{  nullptr };
    	AVCodecParameters *parameters_{  nullptr };
    	struct SwsContext *sws_ctx_{  nullptr };
    
    	AVFrame* frame_{  nullptr };
    	AVFrame* yuv_frame_{  nullptr };
    	AVPacket* packet_{  nullptr };
    
    	bool is_init_{  false };
    	int video_index_{  -1 };
    	std::string file_path_;
    	unsigned char* out_buffer_{  nullptr };
    
    	SDL_Window* window_{  nullptr };
    };

## 测试主程序 ##

#include "VideoPlayer.h"
    
    int main(int argc, char** argv) { 
    	std::string file_path("output.mp4");
    	VideoPlayer player(file_path);
    	if (!player.InitVideoPlayer()) { 
    		return -1;
    	}
    	
    	// 如果使用 Su 版本调用 player.SuShow()
    	// player.SuShow()
    	player.Show();
    	return 0;
    }

## VideoPlayer 实现 ##

#include "VideoPlayer.h"
    
    // 定义刷新事件
    #define SFM_REFRESH_EVENT (SDL_USEREVENT + 1)
    #define SFM_BREAK_EVENT (SDL_USEREVENT + 2)
    
    static bool thread_exit = 0;
    static bool thread_pause = 0;
    
    static int SfpRefreshThread(void *opaque) { 
    	thread_exit = false;
    	thread_pause = false;
    
    	while (!thread_exit)  { 
    		if (!thread_pause) { 
    			SDL_Event event;
    			event.type = SFM_REFRESH_EVENT;
    			SDL_PushEvent(&event);
    		}
    		SDL_Delay(40);
    	}
    	thread_exit = false;
    	thread_pause = false;
    	
    	SDL_Event event;
    	event.type = SFM_BREAK_EVENT;
    	SDL_PushEvent(&event);
    	return 0;
    }
    
    VideoPlayer::VideoPlayer(const std::string& file_path) : file_path_(file_path) { 
    	// 新版的 ffmpeg 已经不需要执行 av_register_all() 了
    	avformat_network_init();
    }
    
    VideoPlayer::~VideoPlayer() { 
    	// 释放所有资源
    	av_frame_free(&yuv_frame_);
    	av_frame_free(&frame_);
    	avcodec_close(codec_ctx_);
    	avformat_close_input(&fmt_ctx_);
    }
    
    bool VideoPlayer::InitVideoPlayer() { 
    	fmt_ctx_ = avformat_alloc_context();
    	if (avformat_open_input(&fmt_ctx_, file_path_.c_str(), nullptr, nullptr) != 0)
    	{ 
    		av_log(nullptr, AV_LOG_ERROR, "Couldn't open input stream");
    		return false;
    	}
    
    	if (avformat_find_stream_info(fmt_ctx_, nullptr) < 0)
    	{ 
    		av_log(nullptr, AV_LOG_ERROR, "Couldn't find stream information");
    		return false;
    	}
    
    	// 老版中根据 AVFormatContext->stream[video_index]->codec 的方式已被弃用
    	// 新版本中使用 av_find_best_stream()， 在第二个参数中指定要找到的流是视频还是音频即可
    	video_index_ = av_find_best_stream(fmt_ctx_, AVMEDIA_TYPE_VIDEO, -1, -1, nullptr, 0);
    
    	if (video_index_ == -1) { 
    		av_log(nullptr, AV_LOG_ERROR, "Didn't find a video stream");
    		return false;
    	}
    
    	parameters_ = fmt_ctx_->streams[video_index_]->codecpar;
    	codec_ = avcodec_find_decoder(parameters_->codec_id);
    	if (!codec_) { 
    		av_log(nullptr, AV_LOG_ERROR, "Couldn't open codec");
    		return false;
    	}
    	codec_ctx_ = avcodec_alloc_context3(codec_);
    	if (avcodec_parameters_to_context(codec_ctx_, parameters_) < 0) { 
    		av_log(nullptr, AV_LOG_ERROR, "Couldn't copy params to context");
    		return false;
    	}
    	
    	// 使用 avcodec_open2 替换原先的 avcodec_open 来打开解码器
    	if (avcodec_open2(codec_ctx_, codec_, nullptr) != 0) { 
    		av_log(nullptr, AV_LOG_ERROR, "Couldn't open codec.");
    		return false;
    	}
    
    	frame_ = av_frame_alloc();
    	yuv_frame_ = av_frame_alloc();
    	
    	// 填充 YUV 数据内容，防止因为 yuv_frame 中没有为 data 分配内存空间而报错
    	out_buffer_ = static_cast<unsigned char*>(av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, codec_ctx_->width, codec_ctx_->height, 1)));
    	av_image_fill_arrays(yuv_frame_->data, yuv_frame_->linesize, 
    						 const_cast<const uint8_t*>(out_buffer_), 
    						 AV_PIX_FMT_YUV420P, 
    						 codec_ctx_->width, codec_ctx_->height, 1);
    	packet_ = av_packet_alloc();
    	
    	// 打印一些关于 output format 的信息，例如比特率，延时之类
    	// 此处第二个参数指定要打印的流的索引
    	av_dump_format(fmt_ctx_, 0, file_path_.c_str(), 0);
    
    	// 创建编码转换器，通过使用 sws_scale 函数将我们读入的视频帧转换为我们需要的格式
    	// 此处的 AV_PIX_FMT_YUV420P 指定要转换成的格式
    	sws_ctx_ = sws_getContext(codec_ctx_->width, codec_ctx_->height, codec_ctx_->pix_fmt, 
    		codec_ctx_->width, codec_ctx_->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, nullptr, nullptr, nullptr);
    
    	is_init_ = true;
    }
    
    void VideoPlayer::Show() { 
    	if (!is_init_) { 
    		av_log(nullptr, AV_LOG_ERROR, "You should init VideoPlayer first.");
    		return;
    	}
    	
    	if (SDL_Init(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER))) { 
    		av_log(nullptr, AV_LOG_ERROR, "Could not initialize SDL - %s", SDL_GetError());
    		return;
    	}
    
    	int h = codec_ctx_->height;
    	int w = codec_ctx_->width;
    
    	window_ = SDL_CreateWindow("__name__", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
    		w, h, SDL_WINDOW_SHOWN);
    
    	if (!window_) { 
    		av_log(nullptr, AV_LOG_ERROR, "SDL: could not create window - exiting:%s", SDL_GetError());
    		return;
    	}
    
    	SDL_Renderer* renderer = SDL_CreateRenderer(window_, -1, 0);
    	SDL_Texture* texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_IYUV, SDL_TEXTUREACCESS_STREAMING, w, h);
    	SDL_Rect rect;
    	rect.x = 0;
    	rect.y = 0;
    	rect.w = w;
    	rect.h = h;
    
    	while (av_read_frame(fmt_ctx_, packet_) >= 0) { 
    	
    		// 我们在此处仅处理视频帧，不处理音频帧
    		if (packet_->stream_index == video_index_) { 
    			avcodec_send_packet(codec_ctx_, packet_);
    			while (avcodec_receive_frame(codec_ctx_, frame_) == 0) { 
    				sws_scale(sws_ctx_, (const unsigned char* const *)frame_->data, frame_->linesize, 0, h, yuv_frame_->data, yuv_frame_->linesize);
    				SDL_UpdateYUVTexture(texture, &rect, yuv_frame_->data[0], yuv_frame_->linesize[0],
    					yuv_frame_->data[1], yuv_frame_->linesize[1],
    					yuv_frame_->data[2], yuv_frame_->linesize[2]);
    				SDL_RenderClear(renderer);
    				SDL_RenderCopy(renderer, texture, nullptr, &rect);
    				SDL_RenderPresent(renderer);
    				SDL_Delay(40);
    			}
    		}
    		av_packet_unref(packet_);
    	}
    
    	// 在解码器上下文中可能还剩有以下没处理的视频，将这些视频处理完后显示
    	while (true) { 
    		int ret = avcodec_send_packet(codec_ctx_, packet_);
    		if (ret != 0) { 
    			break;
    		}
    		while (avcodec_receive_frame(codec_ctx_, frame_) == 0) { 
    			sws_scale(sws_ctx_, (const unsigned char* const *)frame_->data, frame_->linesize, 0, h, yuv_frame_->data, yuv_frame_->linesize);
    			SDL_UpdateYUVTexture(texture, &rect, yuv_frame_->data[0], yuv_frame_->linesize[0],
    				yuv_frame_->data[1], yuv_frame_->linesize[1],
    				yuv_frame_->data[2], yuv_frame_->linesize[2]);
    			SDL_RenderClear(renderer);
    			SDL_RenderCopy(renderer, texture, nullptr, &rect);
    			SDL_RenderPresent(renderer);
    			SDL_Delay(40);
    		}
    	}
    	
    	sws_freeContext(sws_ctx_);
    	SDL_Quit();
    }
    
    void VideoPlayer::SuShow()
    { 
    	if (!is_init_) { 
    		av_log(nullptr, AV_LOG_ERROR, "You should init VideoPlayer first.");
    		return;
    	}
    
    	if (SDL_Init(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER))) { 
    		av_log(nullptr, AV_LOG_ERROR, "Could not initialize SDL - %s", SDL_GetError());
    		return;
    	}
    
    	int h = codec_ctx_->height;
    	int w = codec_ctx_->width;
    
    	window_ = SDL_CreateWindow("__name__", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
    		w, h, SDL_WINDOW_SHOWN);
    
    	if (!window_) { 
    		av_log(nullptr, AV_LOG_ERROR, "SDL: could not create window - exiting:%s", SDL_GetError());
    		return;
    	}
    
    	SDL_Renderer* renderer = SDL_CreateRenderer(window_, -1, 0);
    	SDL_Texture* texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_IYUV, SDL_TEXTUREACCESS_STREAMING, w, h);
    	SDL_Rect rect;
    	rect.x = 0;
    	rect.y = 0;
    	rect.w = w;
    	rect.h = h;
    
    	SDL_Thread *sdl_thread = SDL_CreateThread(SfpRefreshThread, nullptr, nullptr);
    	SDL_Event event;
    
    	while (true) { 
    		SDL_WaitEvent(&event);
    		if (event.type == SFM_REFRESH_EVENT) { 
    		
    			// 当当前的事件是需要刷新显示时，一直循环直到当前的包为视频包时结束
    			while (true) { 
    				if (av_read_frame(fmt_ctx_, packet_) < 0) thread_exit = true;
    				if (packet_->stream_index == video_index_) break;
    			}
    			
    			avcodec_send_packet(codec_ctx_, packet_);
    			while (avcodec_receive_frame(codec_ctx_, frame_) == 0) { 
    				sws_scale(sws_ctx_, (const unsigned char* const *)frame_->data, frame_->linesize, 0, h, yuv_frame_->data, yuv_frame_->linesize);
    				SDL_UpdateYUVTexture(texture, &rect, yuv_frame_->data[0], yuv_frame_->linesize[0],
    					yuv_frame_->data[1], yuv_frame_->linesize[1],
    					yuv_frame_->data[2], yuv_frame_->linesize[2]);
    				SDL_RenderClear(renderer);
    				SDL_RenderCopy(renderer, texture, nullptr, nullptr);
    				SDL_RenderPresent(renderer);
    			}
    			av_packet_unref(packet_);
    		} else if (event.type == SDL_KEYDOWN) { 
    			if (event.key.keysym.sym == SDLK_SPACE) thread_pause = !thread_pause;
    		} else if (event.type == SDL_QUIT) { 
    			thread_exit = true;
    		} else if (event.type == SFM_BREAK_EVENT) { 
    			break;
    		}
    	}
    
    	sws_freeContext(sws_ctx_);
    	SDL_Quit();
    }

[FFMPEG_SDL_ ver2 _SDL2.0]: https://blog.csdn.net/leixiaohua1020/article/details/38868499
[44ed29faa89d3569d052d2100026569c.png]: /images/20210923/d3cfb040c4694864b6169e9e63c66b1f.png