=====================================================
最简单的基于FFmpeg的AVDevice例子文章列表:
最简单的基于FFmpeg的AVDevice例子(读取摄像头)
最简单的基于FFmpeg的AVDevice例子(屏幕录制)
=====================================================
计划写2个有关FFmpeg的libavdevice类库的例子。上篇文章记录了一个基于FFmpeg的Libavdevice类库读取摄像头数据的例子。本篇文章记录一个基于FFmpeg的Libavdevice类库录制屏幕的例子。本文程序录制当前桌面内容并且解码显示出来。有关解码显示方面的代码本文不再详述,可以参考文章:
《100行代码实现最简单的基于FFMPEG+SDL的视频播放器(SDL1.x)》
抓屏方法
上篇文章记录了libavdevice的使用方法,本文不再重复。在Windows系统使用libavdevice抓取屏幕数据有两种方法:gdigrab和dshow。下文分别介绍。
1. gdigrab
gdigrab是FFmpeg专门用于抓取Windows桌面的设备。非常适合用于屏幕录制。它通过不同的输入URL支持两种方式的抓取:
(1)“desktop”:抓取整张桌面。或者抓取桌面中的一个特定的区域。
(2)“title={窗口名称}”:抓取屏幕中特定的一个窗口(目前中文窗口还有乱码问题)。
gdigrab另外还支持一些参数,用于设定抓屏的位置:
offset_x:抓屏起始点横坐标。
offset_y:抓屏起始点纵坐标。
video_size:抓屏的大小。
framerate:抓屏的帧率。
参考的代码如下:
- //Use gdigrab
- AVDictionary* options = NULL;
- //Set some options
- //grabbing frame rate
- //av_dict_set(&options,"framerate","5",0);
- //The distance from the left edge of the screen or desktop
- //av_dict_set(&options,"offset_x","20",0);
- //The distance from the top edge of the screen or desktop
- //av_dict_set(&options,"offset_y","40",0);
- //Video frame size. The default is to capture the full screen
- //av_dict_set(&options,"video_size","640x480",0);
- AVInputFormat *ifmt=av_find_input_format("gdigrab");
- if(avformat_open_input(&pFormatCtx,"desktop",ifmt,&options)!=0){
- printf("Couldn't open input stream.(无法打开输入流)\n");
- return -1;
- }
2. dshow
使用dshow抓屏需要安装抓屏软件:screen-capture-recorder
软件地址:http://sourceforge.net/projects/screencapturer/
下载软件安装完成后,可以指定dshow的输入设备为“screen-capture-recorder”即可。有关dshow设备的使用方法在上一篇文章中已经有详细叙述,这里不再重复。参考的代码如下:
- AVInputFormat *ifmt=av_find_input_format("dshow");
- if(avformat_open_input(&pFormatCtx,"video=screen-capture-recorder",ifmt,NULL)!=0){
- printf("Couldn't open input stream.(无法打开输入流)\n");
- return -1;
- }
注:上述两种抓屏方法也可以直接使用ffmpeg.exe的命令行完成,可以参考文章:
FFmpeg获取DirectShow设备数据(摄像头,录屏)
在Linux下可以使用x11grab抓屏,在MacOS下可以使用avfoundation抓屏,在这里不再详细叙述。
代码
下面直接贴上程序代码:
- /**
- * 最简单的基于FFmpeg的AVDevice例子(屏幕录制)
- * Simplest FFmpeg Device (Screen Capture)
- *
- * 雷霄骅 Lei Xiaohua
- * leixiaohua1020@126.com
- * 中国传媒大学/数字电视技术
- * Communication University of China / Digital TV Technology
- * http://blog.csdn.net/leixiaohua1020
- *
- * 本程序实现了屏幕录制功能。可以录制并播放桌面数据。是基于FFmpeg
- * 的libavdevice类库最简单的例子。通过该例子,可以学习FFmpeg中
- * libavdevice类库的使用方法。
- * 本程序在Windows下可以使用2种方式录制屏幕:
- * 1.gdigrab: Win32下的基于GDI的屏幕录制设备。
- * 抓取桌面的时候,输入URL为“desktop”。
- * 2.dshow: 使用Directshow。注意需要安装额外的软件screen-capture-recorder
- * 在Linux下可以使用x11grab录制屏幕。
- * 在MacOS下可以使用avfoundation录制屏幕。
- *
- * This software capture screen of computer. It's the simplest example
- * about usage of FFmpeg's libavdevice Library.
- * It's suiltable for the beginner of FFmpeg.
- * This software support 2 methods to capture screen in Microsoft Windows:
- * 1.gdigrab: Win32 GDI-based screen capture device.
- * Input URL in avformat_open_input() is "desktop".
- * 2.dshow: Use Directshow. Need to install screen-capture-recorder.
- * It use x11grab to capture screen in Linux.
- * It use avfoundation to capture screen in MacOS.
- */
- #include <stdio.h>
- #define __STDC_CONSTANT_MACROS
- #ifdef _WIN32
- //Windows
- extern "C"
- {
- #include "libavcodec/avcodec.h"
- #include "libavformat/avformat.h"
- #include "libswscale/swscale.h"
- #include "libavdevice/avdevice.h"
- #include "SDL/SDL.h"
- };
- #else
- //Linux...
- #ifdef __cplusplus
- extern "C"
- {
- #endif
- #include <libavcodec/avcodec.h>
- #include <libavformat/avformat.h>
- #include <libswscale/swscale.h>
- #include <libavdevice/avdevice.h>
- #include <SDL/SDL.h>
- #ifdef __cplusplus
- };
- #endif
- #endif
- //Output YUV420P
- #define OUTPUT_YUV420P 0
- //'1' Use Dshow
- //'0' Use GDIgrab
- #define USE_DSHOW 0
- //Refresh Event
- #define SFM_REFRESH_EVENT (SDL_USEREVENT + 1)
- int thread_exit=0;
- int sfp_refresh_thread(void *opaque)
- {
- while (thread_exit==0) {
- SDL_Event event;
- event.type = SFM_REFRESH_EVENT;
- SDL_PushEvent(&event);
- SDL_Delay(40);
- }
- return 0;
- }
- //Show Dshow Device
- void show_dshow_device(){
- AVFormatContext *pFormatCtx = avformat_alloc_context();
- AVDictionary* options = NULL;
- av_dict_set(&options,"list_devices","true",0);
- AVInputFormat *iformat = av_find_input_format("dshow");
- printf("========Device Info=============\n");
- avformat_open_input(&pFormatCtx,"video=dummy",iformat,&options);
- printf("================================\n");
- }
- //Show AVFoundation Device
- void show_avfoundation_device(){
- AVFormatContext *pFormatCtx = avformat_alloc_context();
- AVDictionary* options = NULL;
- av_dict_set(&options,"list_devices","true",0);
- AVInputFormat *iformat = av_find_input_format("avfoundation");
- printf("==AVFoundation Device Info===\n");
- avformat_open_input(&pFormatCtx,"",iformat,&options);
- printf("=============================\n");
- }
- int main(int argc, char* argv[])
- {
- AVFormatContext *pFormatCtx;
- int i, videoindex;
- AVCodecContext *pCodecCtx;
- AVCodec *pCodec;
- av_register_all();
- avformat_network_init();
- pFormatCtx = avformat_alloc_context();
- //Open File
- //char filepath[]="src01_480x272_22.h265";
- //avformat_open_input(&pFormatCtx,filepath,NULL,NULL)
- //Register Device
- avdevice_register_all();
- //Windows
- #ifdef _WIN32
- #if USE_DSHOW
- //Use dshow
- //
- //Need to Install screen-capture-recorder
- //screen-capture-recorder
- //Website: http://sourceforge.net/projects/screencapturer/
- //
- AVInputFormat *ifmt=av_find_input_format("dshow");
- if(avformat_open_input(&pFormatCtx,"video=screen-capture-recorder",ifmt,NULL)!=0){
- printf("Couldn't open input stream.\n");
- return -1;
- }
- #else
- //Use gdigrab
- AVDictionary* options = NULL;
- //Set some options
- //grabbing frame rate
- //av_dict_set(&options,"framerate","5",0);
- //The distance from the left edge of the screen or desktop
- //av_dict_set(&options,"offset_x","20",0);
- //The distance from the top edge of the screen or desktop
- //av_dict_set(&options,"offset_y","40",0);
- //Video frame size. The default is to capture the full screen
- //av_dict_set(&options,"video_size","640x480",0);
- AVInputFormat *ifmt=av_find_input_format("gdigrab");
- if(avformat_open_input(&pFormatCtx,"desktop",ifmt,&options)!=0){
- printf("Couldn't open input stream.\n");
- return -1;
- }
- #endif
- #elif defined linux
- //Linux
- AVDictionary* options = NULL;
- //Set some options
- //grabbing frame rate
- //av_dict_set(&options,"framerate","5",0);
- //Make the grabbed area follow the mouse
- //av_dict_set(&options,"follow_mouse","centered",0);
- //Video frame size. The default is to capture the full screen
- //av_dict_set(&options,"video_size","640x480",0);
- AVInputFormat *ifmt=av_find_input_format("x11grab");
- //Grab at position 10,20
- if(avformat_open_input(&pFormatCtx,":0.0+10,20",ifmt,&options)!=0){
- printf("Couldn't open input stream.\n");
- return -1;
- }
- #else
- show_avfoundation_device();
- //Mac
- AVInputFormat *ifmt=av_find_input_format("avfoundation");
- //Avfoundation
- //[video]:[audio]
- if(avformat_open_input(&pFormatCtx,"1",ifmt,NULL)!=0){
- printf("Couldn't open input stream.\n");
- return -1;
- }
- #endif
- if(avformat_find_stream_info(pFormatCtx,NULL)<0)
- {
- printf("Couldn't find stream information.\n");
- return -1;
- }
- videoindex=-1;
- for(i=0; i<pFormatCtx->nb_streams; i++)
- if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
- {
- videoindex=i;
- break;
- }
- if(videoindex==-1)
- {
- printf("Didn't find a video stream.\n");
- return -1;
- }
- pCodecCtx=pFormatCtx->streams[videoindex]->codec;
- pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
- if(pCodec==NULL)
- {
- printf("Codec not found.\n");
- return -1;
- }
- if(avcodec_open2(pCodecCtx, pCodec,NULL)<0)
- {
- printf("Could not open codec.\n");
- return -1;
- }
- AVFrame *pFrame,*pFrameYUV;
- pFrame=av_frame_alloc();
- pFrameYUV=av_frame_alloc();
- //uint8_t *out_buffer=(uint8_t *)av_malloc(avpicture_get_size(PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height));
- //avpicture_fill((AVPicture *)pFrameYUV, out_buffer, PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);
- //SDL----------------------------
- if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
- printf( "Could not initialize SDL - %s\n", SDL_GetError());
- return -1;
- }
- int screen_w=640,screen_h=360;
- const SDL_VideoInfo *vi = SDL_GetVideoInfo();
- //Half of the Desktop's width and height.
- screen_w = vi->current_w/2;
- screen_h = vi->current_h/2;
- SDL_Surface *screen;
- screen = SDL_SetVideoMode(screen_w, screen_h, 0,0);
- if(!screen) {
- printf("SDL: could not set video mode - exiting:%s\n",SDL_GetError());
- return -1;
- }
- SDL_Overlay *bmp;
- bmp = SDL_CreateYUVOverlay(pCodecCtx->width, pCodecCtx->height,SDL_YV12_OVERLAY, screen);
- SDL_Rect rect;
- rect.x = 0;
- rect.y = 0;
- rect.w = screen_w;
- rect.h = screen_h;
- //SDL End------------------------
- int ret, got_picture;
- AVPacket *packet=(AVPacket *)av_malloc(sizeof(AVPacket));
- #if OUTPUT_YUV420P
- FILE *fp_yuv=fopen("output.yuv","wb+");
- #endif
- struct SwsContext *img_convert_ctx;
- img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
- //------------------------------
- SDL_Thread *video_tid = SDL_CreateThread(sfp_refresh_thread,NULL);
- //
- SDL_WM_SetCaption("Simplest FFmpeg Grab Desktop",NULL);
- //Event Loop
- SDL_Event event;
- for (;;) {
- //Wait
- SDL_WaitEvent(&event);
- if(event.type==SFM_REFRESH_EVENT){
- //------------------------------
- if(av_read_frame(pFormatCtx, packet)>=0){
- if(packet->stream_index==videoindex){
- ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
- if(ret < 0){
- printf("Decode Error.\n");
- return -1;
- }
- if(got_picture){
- SDL_LockYUVOverlay(bmp);
- pFrameYUV->data[0]=bmp->pixels[0];
- pFrameYUV->data[1]=bmp->pixels[2];
- pFrameYUV->data[2]=bmp->pixels[1];
- pFrameYUV->linesize[0]=bmp->pitches[0];
- pFrameYUV->linesize[1]=bmp->pitches[2];
- pFrameYUV->linesize[2]=bmp->pitches[1];
- sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize);
- #if OUTPUT_YUV420P
- int y_size=pCodecCtx->width*pCodecCtx->height;
- fwrite(pFrameYUV->data[0],1,y_size,fp_yuv); //Y
- fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv); //U
- fwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv); //V
- #endif
- SDL_UnlockYUVOverlay(bmp);
- SDL_DisplayYUVOverlay(bmp, &rect);
- }
- }
- av_free_packet(packet);
- }else{
- //Exit Thread
- thread_exit=1;
- break;
- }
- }else if(event.type==SDL_QUIT){
- thread_exit=1;
- break;
- }
- }
- sws_freeContext(img_convert_ctx);
- #if OUTPUT_YUV420P
- fclose(fp_yuv);
- #endif
- SDL_Quit();
- //av_free(out_buffer);
- av_free(pFrameYUV);
- avcodec_close(pCodecCtx);
- avformat_close_input(&pFormatCtx);
- return 0;
- }
结果
程序的运行效果如下。这个运行结果还是十分有趣的,会出现一个屏幕“嵌套”在另一个屏幕里面的现象,环环相套。- #define OUTPUT_YUV420P 0
可以通过下面的宏定义来确定使用GDIGrab或者是Dshow打开摄像头:
- //'1' Use Dshow
- //'0' Use GDIgrab
- #define USE_DSHOW 0
Simplest FFmpeg Device
项目主页
SourceForge:https://sourceforge.net/projects/simplestffmpegdevice/
Github:https://github.com/leixiaohua1020/simplest_ffmpeg_device
开源中国:http://git.oschina.net/leixiaohua1020/simplest_ffmpeg_device
http://download.csdn.net/detail/leixiaohua1020/7994049
注:
本工程包含两个基于FFmpeg的libavdevice的例子:
simplest_ffmpeg_grabdesktop:屏幕录制。
simplest_ffmpeg_readcamera:读取摄像头
更新-1.1(2015.1.9)=========================================
该版本中,修改了SDL的显示方式,弹出的窗口可以移动了。
CSDN下载地址:http://download.csdn.net/detail/leixiaohua1020/8344695
更新-1.2 (2015.2.13)=========================================
这次考虑到了跨平台的要求,调整了源代码。经过这次调整之后,源代码可以在以下平台编译通过:
VC++:打开sln文件即可编译,无需配置。
cl.exe:打开compile_cl.bat即可命令行下使用cl.exe进行编译,注意可能需要按照VC的安装路径调整脚本里面的参数。编译命令如下。
- ::VS2010 Environment
- call "D:\Program Files\Microsoft Visual Studio 10.0\VC\vcvarsall.bat"
- ::include
- @set INCLUDE=include;%INCLUDE%
- ::lib
- @set LIB=lib;%LIB%
- ::compile and link
- cl simplest_ffmpeg_grabdesktop.cpp /MD /link SDL.lib SDLmain.lib avcodec.lib ^
- avformat.lib avutil.lib avdevice.lib avfilter.lib postproc.lib swresample.lib swscale.lib ^
- /SUBSYSTEM:WINDOWS /OPT:NOREF
MinGW:MinGW命令行下运行compile_mingw.sh即可使用MinGW的g++进行编译。编译命令如下。
- g++ simplest_ffmpeg_grabdesktop.cpp -g -o simplest_ffmpeg_grabdesktop.exe \
- -I /usr/local/include -L /usr/local/lib \
- -lmingw32 -lSDLmain -lSDL -lavformat -lavcodec -lavutil -lavdevice -lswscale
GCC(Linux):Linux命令行下运行compile_gcc.sh即可使用GCC进行编译。编译命令如下。
- gcc simplest_ffmpeg_grabdesktop.cpp -g -o simplest_ffmpeg_grabdesktop.out \
- -I /usr/local/include -L /usr/local/lib -lSDLmain -lSDL -lavformat -lavcodec -lavutil -lavdevice -lswscale
GCC(MacOS):MacOS命令行下运行compile_gcc_mac.sh即可使用GCC进行编译。Mac的GCC和Linux的GCC差别不大,但是使用SDL1.2的时候,必须加上“-framework Cocoa”参数,否则编译无法通过。编译命令如下。
- gcc simplest_ffmpeg_grabdesktop.cpp -g -o simplest_ffmpeg_grabdesktop.out \
- -framework Cocoa -I /usr/local/include -L /usr/local/lib -lSDLmain -lSDL -lavformat -lavcodec -lavutil -lavdevice -lswscale
PS:相关的编译命令已经保存到了工程文件夹中