基于 FFMPEG + SDL2 的视频播放器
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） 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
VideoPlayer 类声明
#pragma once#ifdef __cplusplusextern "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();}
谁践踏了优雅
不念不忘少年蓝@
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小鱼儿
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