音视频入门-6-ffmpeg小实验-从v4l2层获取PC ubuntu摄像头图像

0.　　进行本代码实验的前提

确保已经在ubuntu内正确安装了ffmpeg

手把手安装教程可以参考我的另一篇博文《音视频入门-4-ffmpeg命令快速体验音视频开发/ ffmpeg编译过程经历的99八十一难》

　　   https://www.cnblogs.com/happybirthdaytoyou/p/14256260.html

1.   直接上代码

readdevice.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include "avformat.h"
#include "avcodec.h"
#include "avdevice.h"

char* input_name = "video4linux2";
char* file_name  = "/dev/video0";
char* out_file   = "picture";

void captureOneFrame(void){
    AVFormatContext *fmtCtx = NULL;
    AVPacket *packet;
    AVInputFormat *inputFmt;
    FILE *fp;
    int ret;

    inputFmt = av_find_input_format(input_name);    

    if (inputFmt == NULL)    {
        printf("can not find_input_format\n");
        return;
    }    

    if (avformat_open_input( &fmtCtx, file_name, inputFmt, NULL) < 0){
        printf("can not open_input_file\n");         return;
    }
    /* print device information*/
    av_dump_format(fmtCtx, 0, file_name, 0);

    packet = (AVPacket *)av_malloc(sizeof(AVPacket));
    av_read_frame(fmtCtx, packet);
    printf("data length = %d\n",packet->size);   

    fp = fopen(out_file, "wb");
    if (fp < 0)    {
        printf("open frame data file failed\n");
        return ;
    }    

    fwrite(packet->data, 1, packet->size, fp);    

    fclose(fp);
    av_free_packet(packet);
    avformat_close_input(&fmtCtx);
 } 

int main(void){
    avcodec_register_all();
    avdevice_register_all();
    captureOneFrame();
    return 0;
}

makefile:

OUT_APP         = test
INCLUDE_PATH = /usr/local/ffmpeg/include/
INCLUDE = -I$(INCLUDE_PATH) -I$(INCLUDE_PATH)libavutil/ -I$(INCLUDE_PATH)libavdevice/ \
            -I$(INCLUDE_PATH)libavcodec/ -I$(INCLUDE_PATH)libswresample \
            -I$(INCLUDE_PATH)libavfilter/ -I$(INCLUDE_PATH)libavformat \
            -I$(INCLUDE_PATH)libswscale/

LIB_PATH = /usr/local/ffmpeg/lib/
FFMPEG_LIBS = -L$(LIB_PATH) -lavformat -lavutil -lavdevice -lavcodec -lswresample -lavfilter -lswscale
SDL_LIBS    =
LIBS        = $(FFMPEG_LIBS)$(SDL_LIBS)

COMPILE_OPTS = $(INCLUDE)
C              = c
OBJ          = o
C_COMPILER   = cc
C_FLAGS      = $(COMPILE_OPTS) $(CPPFLAGS) $(CFLAGS)

LINK          = cc -o
LINK_OPTS    = -lz -lm  -lpthread
LINK_OBJ     = readdevice.o 

.$(C).$(OBJ):
    $(C_COMPILER) -c -g $(C_FLAGS) $<

$(OUT_APP): $(LINK_OBJ)
    $(LINK)$@  $(LINK_OBJ)  $(LIBS) $(LINK_OPTS)

clean:
        -rm -rf *.$(OBJ) $(OUT_APP) core *.core *~  picture

2.

输出的图片格式是依你使用的电脑摄像头硬件决定的，每个人可能都不一样。

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