一、程序的邏輯主要分兩部分：

1、通過video4linux2讀取攝像頭的V4L2_PIX_FMT_YUYV格式的原始數(shù)據(jù)

2、把V4L2_PIX_FMT_YUYV格式的數(shù)據(jù)轉(zhuǎn)換成AV_PIX_FMT_YUV422P格式的yuv數(shù)據(jù)，并存放在AVFrame結(jié)構(gòu)中； ? ? ? ? 把AVFrame結(jié)構(gòu)送到編碼器；

? ? ? 收取編碼后的h264數(shù)據(jù)流，并存到文件中

二、代碼中主要用到的庫：

1、通過一個叫uvccapture-0.5庫（我直接改了里面的代碼），獲取攝像頭的V4L2_PIX_FMT_YUYV格式數(shù)據(jù)。

2、通過libav編碼

三、主要代碼：

/** main.cpp** Created on: 2014-3-2* Author: xy*/#include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <time.h> #include <linux/videodev2.h> //ffplay -f video4linux2 -framerate 30 -video_size hd720 /dev/video0 #ifdef __cplusplus extern "C" { #endif #define __STDC_CONSTANT_MACROS #ifdef _STDINT_H #undef _STDINT_H #endif # include <stdint.h> #include "libavformat/avformat.h" #include "libavdevice/avdevice.h" #include <libavutil/imgutils.h> #include <libavutil/opt.h>#ifdef __cplusplus } #endif //輸入設(shè)備 #include "v4l2uvc.h" int main() {//v4l2 valchar *videodevice = "/dev/video0";int width = 640; //320;int height = 480; //240;int brightness = 0, contrast = 0, saturation = 0, gain = 0;int quality = 95;int format = V4L2_PIX_FMT_YUYV;struct vdIn *videoIn;int grabmethod = 1;//video encoder initavcodec_register_all();AVCodec *codec;AVCodecContext *c = NULL;int i, ret, x, y, got_output;FILE *f;AVFrame *frame;AVPacket pkt;uint8_t endcode[] = { 0, 0, 1, 0xb7 };char filename[] = "test.264";printf("Encode video file %s\n", filename);/* find the mpeg1 video encoder */codec = avcodec_find_encoder(AV_CODEC_ID_H264);if (!codec) {fprintf(stderr, "Codec not found\n");exit(1);}c = avcodec_alloc_context3(codec);if (!c) {fprintf(stderr, "Could not allocate video codec context\n");exit(1);}/* put sample parameters */c->bit_rate = 400000;/* resolution must be a multiple of two */c->width = width; // 352;c->height = height; // 288;/* frames per second */c->time_base = (AVRational) {1,10/*25*/};c->gop_size = 10; /* emit one intra frame every ten frames */c->max_b_frames = 0; //1c->pix_fmt = AV_PIX_FMT_YUV422P; //v4l2是這個格式 AV_PIX_FMT_YUV420P;//av_opt_set(c->priv_data, "preset", "slow", 0);av_opt_set(c->priv_data, "tune", "zerolatency", 0); //這個可以讓libav不緩存視頻幀/********************************************************************************* 有兩個地方影響libav是不是緩存編碼后的視頻幀，也就是影響實時性：* 1、av_opt_set(c->priv_data, "tune", "zerolatency", 0);這個比較主要。* 2、參數(shù)中有c->max_b_frames = 1;如果這個幀設(shè)為0,就沒有B幀了，編碼會很快的。********************************************************************************//* open it */if (avcodec_open2(c, codec, NULL) < 0) {fprintf(stderr, "Could not open codec\n");exit(1);}f = fopen(filename, "wb");if (!f) {fprintf(stderr, "Could not open %s\n", filename);exit(1);}frame = av_frame_alloc();if (!frame) {fprintf(stderr, "Could not allocate video frame\n");exit(1);}frame->format = c->pix_fmt;frame->width = c->width;frame->height = c->height;/* the image can be allocated by any means and av_image_alloc() is* just the most convenient way if av_malloc() is to be used */ret = av_image_alloc(frame->data, frame->linesize, c->width, c->height,c->pix_fmt, 32);if (ret < 0) {fprintf(stderr, "Could not allocate raw picture buffer\n");exit(1);}//v4l2 initvideoIn = (struct vdIn *) calloc(1, sizeof(struct vdIn));if (init_videoIn(videoIn, (char *) videodevice, width, height, format,grabmethod) < 0)exit(1);printf("w:%d,h:%d\n", c->width, c->height);time_t timep;timep = time(NULL);printf("%s\n", asctime(gmtime(&timep)));for (i = 0; i < 100; i++) {//usleep(200000);//從v4l2中獲取數(shù)據(jù)格式為AV_PIX_FMT_YUV422Pif (uvcGrab(videoIn) < 0) {fprintf(stderr, "Error grabbing\n");close_v4l2(videoIn);free(videoIn);exit(1);}unsigned char *yuyv = videoIn->framebuffer;//把數(shù)據(jù)復(fù)制到libav想要的結(jié)構(gòu)中av_init_packet(&pkt);pkt.data = NULL; // packet data will be allocated by the encoderpkt.size = 0;printf("debug!!!");fflush(stdout); #if 0/* prepare a dummy image *//* Y */for (y = 0; y < c->height; y++) {for (x = 0; x < c->width; x++) {frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;}}/* Cb and Cr */for (y = 0; y < c->height/2; y++) {for (x = 0; x < c->width/2; x++) {frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;}} #else/* prepare image *//* Y Cb Rb */for (y = 0; y < c->height; y++) {for (x = 0; x < c->width; x++) {frame->data[0][y * frame->linesize[0] + x] = yuyv[y* frame->linesize[0] * 2 + 2 * x];}}/* Cb and Cr */for (y = 0; y < c->height; y++) {for (x = 0; x < c->width / 2; x++) {//frame->data[0][y * frame->linesize[0] + 2*x ] = yuyv[y*frame->linesize[0]*4+4*x];//frame->data[0][y * frame->linesize[0] + 2*x+1] = yuyv[y*frame->linesize[0]*4+4*x+2];frame->data[1][y * frame->linesize[1] + x] = yuyv[y* frame->linesize[1] * 4 + 4 * x + 1];frame->data[2][y * frame->linesize[2] + x] = yuyv[y* frame->linesize[2] * 4 + 4 * x + 3];}} #endifframe->pts = i;/* encode the image */ret = avcodec_encode_video2(c, &pkt, frame, &got_output);if (ret < 0) {fprintf(stderr, "Error encoding frame\n");exit(1);}if (got_output) {printf("Write frame %3d (size=%5d)\n", i, pkt.size);fwrite(pkt.data, 1, pkt.size, f);av_free_packet(&pkt);}//編碼}/* get the delayed frames */for (got_output = 1; got_output; i++) {fflush(stdout);ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);if (ret < 0) {fprintf(stderr, "Error encoding frame\n");exit(1);}if (got_output) {printf("Write frame %3d (size=%5d)\n", i, pkt.size);fwrite(pkt.data, 1, pkt.size, f);av_free_packet(&pkt);}}timep = time(NULL);printf("%s\n", asctime(gmtime(&timep)));/* add sequence end code to have a real mpeg file */fwrite(endcode, 1, sizeof(endcode), f);fclose(f);avcodec_close(c);av_free(c);av_freep(&frame->data[0]);av_frame_free(&frame);printf("111\n");free(videoIn); }
想運行代碼的朋友可以通過這個文章：

http://blog.csdn.net/xyyangkun/article/details/20456725

編譯用到的libav庫

在通過改工程中的makefile：

LIBAVDIR=/home/xy/mywork/av/libav-2014-03-02

指定libav庫的位置就可以了。

使用的讀攝像頭數(shù)據(jù)的代碼出處：

http://staticwave.ca/source/uvccapture/uvccapture-0.5.tar.bz2

庫的工程在代碼在：

http://download.csdn.net/detail/xyyangkun/6990791

所在工程已上傳到github:

https://github.com/xyyangkun/read_encoder_sender

提交版本：2e60986a438e731aa53ca7d54bc492c521e7b5bc

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總結(jié)

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