标签：ffmpeg libavdevice 编程 摄像头 directshow
FFmpeg中有一个和多媒体设备交互的类库：Libavdevice。使用这个库可以读取电脑（或者其他设备上）的多媒体设备的数据，或者输出数据到指定的多媒体设备上。alsaLibavdevice支持以下设备作为输出端：
avfoundation
bktr
dshow
dv1394
fbdev
gdigrab
iec61883
jack
lavfi
libcdio
libdc1394
openal
oss
pulse
qtkit
sndio
video4linux2, v4l2
vfwcap
x11grab
decklink
alsa
caca
decklink
fbdev
opengl
oss
pulse
sdl
sndio
xv
本文主要记录使用libavdevice需要注意的步骤。
首先，使用libavdevice的时候需要包含其头文件：#include "libavdevice/avdevice.h"然后，在程序中需要注册libavdevice：
avdevice_register_all();
AVFormatContext *pFormatCtx = avformat_alloc_context(); avformat_open_input(&pFormatCtx, "test.h265",NULL,NULL);
AVFormatContext *pFormatCtx = avformat_alloc_context();
AVInputFormat *ifmt=av_find_input_format("vfwcap");
avformat_open_input(&pFormatCtx, 0, ifmt,NULL);AVFormatContext *pFormatCtx = avformat_alloc_context();
AVInputFormat *ifmt=av_find_input_format("dshow");
avformat_open_input(&pFormatCtx,"video=Integrated Camera",ifmt,NULL) ;（1） 通过FFmpeg编程实现。使用如下代码：
//Show 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");
}
ffmpeg -list_devices true -f dshow -i dummy
执行的结果如下图所示：
/**
* 最简单的基于FFmpeg的AVDevice例子（读取摄像头）
* Simplest FFmpeg Device (Read Camera)
*
* 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
*
* 本程序实现了本地摄像头数据的获取解码和显示。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种方式读取摄像头数据：
* 1.VFW: Video for Windows 屏幕捕捉设备。注意输入URL是设备的序号，
* 从0至9。
* 2.dshow: 使用Directshow。注意作者机器上的摄像头设备名称是
* “Integrated Camera”，使用的时候需要改成自己电脑上摄像头设
* 备的名称。
* 在Linux下则可以使用video4linux2读取摄像头设备。
*
* This software read data from Computer‘s Camera and play it.
* 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 read camera in Microsoft Windows:
* 1.gdigrab: VfW (Video for Windows) capture input device.
* The filename passed as input is the capture driver number,
* ranging from 0 to 9.
* 2.dshow: Use Directshow. Camera‘s name in author‘s computer is
* "Integrated Camera".
* It use video4linux2 to read Camera in Linux.
*
*/
#include "stdafx.h"
extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavdevice/avdevice.h"
//SDL
#include "sdl/SDL.h"
#include "sdl/SDL_thread.h"
};
//Output YUV420P
#define OUTPUT_YUV420P 0
//‘1‘ Use Dshow
//‘0‘ Use VFW
#define USE_DSHOW 0
//Show 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 Device Option
void show_dshow_device_option(){
AVFormatContext *pFormatCtx = avformat_alloc_context();
AVDictionary* options = NULL;
av_dict_set(&options,"list_options","true",0);
AVInputFormat *iformat = av_find_input_format("dshow");
printf("Device Option Info======\n");
avformat_open_input(&pFormatCtx,"video=Integrated Camera",iformat,&options);
printf("========================\n");
}
//Show VFW Device
void show_vfw_device(){
AVFormatContext *pFormatCtx = avformat_alloc_context();
AVInputFormat *iformat = av_find_input_format("vfwcap");
printf("VFW Device Info======\n");
avformat_open_input(&pFormatCtx,"list",iformat,NULL);
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();
//Show Dshow Device
show_dshow_device();
//Show Device Options
show_dshow_device_option();
//Show VFW Options
show_vfw_device();
//Windows
#ifdef _WIN32
#if USE_DSHOW
AVInputFormat *ifmt=av_find_input_format("dshow");
//Set own video device‘s name
if(avformat_open_input(&pFormatCtx,"video=Integrated Camera",ifmt,NULL)!=0){
printf("Couldn‘t open input stream.（无法打开输入流）\n");
return -1;
}
#else
AVInputFormat *ifmt=av_find_input_format("vfwcap");
if(avformat_open_input(&pFormatCtx,"0",ifmt,NULL)!=0){
printf("Couldn‘t open input stream.（无法打开输入流）\n");
return -1;
}
#endif
#endif
//Linux
#ifdef linux
AVInputFormat *ifmt=av_find_input_format("video4linux2");
if(avformat_open_input(&pFormatCtx,"/dev/video0",ifmt,NULL)!=0){
printf("Couldn‘t open input stream.（无法打开输入流）\n");
return -1;
}
#endif
if(avformat_find_stream_info(pFormatCtx,NULL)<0)
{
printf("Couldn‘t find stream information.（无法获取流信息）\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("Couldn‘t find a video stream.（没有找到视频流）\n");
return -1;
}
pCodecCtx=pFormatCtx->streams[videoindex]->codec;
pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
if(pCodec==NULL)
{
printf("Codec not found.（没有找到解码器）\n");
return -1;
}
if(avcodec_open2(pCodecCtx, pCodec,NULL)<0)
{
printf("Could not open codec.（无法打开解码器）\n");
return -1;
}
AVFrame *pFrame,*pFrameYUV;
pFrame=avcodec_alloc_frame();
pFrameYUV=avcodec_alloc_frame();
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=0,screen_h=0;
SDL_Surface *screen;
screen_w = pCodecCtx->width;
screen_h = pCodecCtx->height;
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;
//SDL End------------------------
int ret, got_picture;
AVPacket *packet=(AVPacket *)av_malloc(sizeof(AVPacket));
//Output Information-----------------------------
printf("File Information（文件信息）---------------------\n");
av_dump_format(pFormatCtx,0,NULL,0);
printf("-------------------------------------------------\n");
#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);
//------------------------------
while(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.（解码错误）\n");
return -1;
}
if(got_picture)
{
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_LockYUVOverlay(bmp);
bmp->pixels[0]=pFrameYUV->data[0];
bmp->pixels[2]=pFrameYUV->data[1];
bmp->pixels[1]=pFrameYUV->data[2];
bmp->pitches[0]=pFrameYUV->linesize[0];
bmp->pitches[2]=pFrameYUV->linesize[1];
bmp->pitches[1]=pFrameYUV->linesize[2];
SDL_UnlockYUVOverlay(bmp);
rect.x = 0;
rect.y = 0;
rect.w = screen_w;
rect.h = screen_h;
SDL_DisplayYUVOverlay(bmp, &rect);
//Delay 40ms
SDL_Delay(40);
}
}
av_free_packet(packet);
}
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;
}
程序的运行效果如下。输出了摄像头的数据。
#define OUTPUT_YUV420P 0
https://sourceforge.net/projects/simplestffmpegdevice/
CSDN项目下载地址：
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。
最简单的基于FFmpeg的AVDevice例子（读取摄像头）
标签：ffmpeg libavdevice 编程 摄像头 directshow
原文地址：http://blog.csdn.net/leixiaohua1020/article/details/39702113
