视频编解码---x264用于编码，ffmpeg用于解码

项目要用到视频编解码，最近半个月都在搞，说实话真是走了很多弯路，浪费了很多时间。将自己的最终成果记录于此，期望会给其他人提供些许帮助。  

参考教程：

http://ffmpeg.org/trac/ffmpeg/wiki/UbuntuCompilationGuide安装ffmpeg和x264，官方权威教程（注意不要用命令行安装，会少很多库的。编译安装最保险）

http://blog.csdn.net/zgyulongfei/article/details/7526249采集与编码的教程

http://www.cnblogs.com/fojian/archive/2012/09/01/2666627.html编码的好文章

http://my.oschina.net/u/555701/blog/56616?p=2#comments-解码的好文章 

整体过程流程如下：

显而易见，整个过程分为三个部分：采集、编码、解码。

1.        采集视频

我是利用USB摄像头采集视频的，我的摄像头只支持YUV422格式的图像采集，因为x264编码库只能编码YUV420P(planar)格式，因此在采集到yuv422格式的图像数据后要变换成yuv420p格式。

采集视频使用官方的那个采集程序，稍加修改即可，具体点说就是修改

static void  process_image (const char * p) ;函数

参数p指向一帧采集图像的yuv数据。

 

关于YUV格式和RGB格式，网上有很多教程。

在这儿，我讲一下自己的理解。

假设有一幅4*4分辨率的图片，如下：

1	2	3	4
5	6	7	8
9	10	11	12
13	14	15	16

每个像素是由YUV数据构成，假设如下：

Y1	U1	V1	Y2	U2	V2	Y3	U3	V3	Y4	U4	V4
Y5	U5	V5	Y6	U6	V6	Y7	U7	V7	Y8	U8	V8
Y9	U9	V9	Y10	U10	V10	Y11	U11	V11	Y12	U12	V12
Y13	U13	V13	Y14	U14	V14	Y15	U15	V15	Y16	U16	V16

YUV422图像是这样的，每个像素采集Y，UV每隔两个像素采集一次：

Packed格式的YUV420是这样的，每个像素采集Y，UV隔行采集，每行是每两个像素采集一次：

以上几种格式存储就是按照从左到右，从上到下顺序存储的。

我想要得到是planar格式的YUV420，即在一段连续的内存中，先存储所有的Y，接着是所有的U，最后是所有的V。

修改后的 process_image函数如下：

static void
process_image                   (const char *           p)
{
        //fputc ('.', stdout);
    //convert yuv422 to yuv420p
            char *y=yuv420p;
            char *u=&yuv420p[IMAGE_WIDTH*IMAGE_HEIGHT];
            char *v=&yuv420p[IMAGE_WIDTH*IMAGE_HEIGHT+IMAGE_WIDTH*IMAGE_HEIGHT/4];

            int i=0,j=0,l=0;
            for(j=0;j<IMAGE_HEIGHT;j++)
                for(i=0;i<IMAGE_WIDTH*2;i++,l++){

                    if(j%2==0){//even line to sample U-Chriminance
                        if(l==1){//sample U-Chriminance
                            *u=p[j*IMAGE_WIDTH*2+i];
                            u++;
                         }
                         else if(l==3){//abandon V-Chroma
                            l=-1;
                            continue;

                         }
                         else{
                            *y=p[j*IMAGE_WIDTH*2+i];
                            ++y;
                         }
                    }

                    else if(j%2==1){//odd lines to sample  V-Chroma
                        if(l==1){
                            continue;
                        }
                        else if(l==3){
                            l=-1;
                            *v=p[j*IMAGE_WIDTH*2+i];
                            ++v;
                        }
                        else {
                            *y=p[j*IMAGE_WIDTH*2+i];
                            ++y;
                        }

                    }

                }

            fwrite(yuv420p,IMAGE_WIDTH*IMAGE_HEIGHT*3>>1,1,fp_yuv420p);

            fflush (stdout);

}

2.编码

采用x264编码库编码yuv420p文件。

程序如下：

#include <stdint.h>
#include <x264.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>

#define DEBUG 0

#define CLEAR(x) (memset((&x),0,sizeof(x)))
#define IMAGE_WIDTH   320
#define IMAGE_HEIGHT  240
#define ENCODER_PRESET "veryfast"
#define ENCODER_TUNE   "zerolatency"
#define ENCODER_PROFILE  "baseline"
#define ENCODER_COLORSPACE X264_CSP_I420

typedef struct my_x264_encoder{
    x264_param_t  * x264_parameter;
    char parameter_preset[20];
    char parameter_tune[20];
    char parameter_profile[20];
    x264_t  * x264_encoder;
    x264_picture_t * yuv420p_picture;
    long colorspace;
    unsigned char *yuv;
    x264_nal_t * nal;
} my_x264_encoder;

char *read_filename="yuv420p.yuv";
char *write_filename="encode.h264";

int
main(int argc ,char **argv){
    int ret;
    int fd_read,fd_write;
    my_x264_encoder * encoder=(my_x264_encoder *)malloc(sizeof(my_x264_encoder));
    if(!encoder){
        printf("cannot malloc my_x264_encoder !\n");
        exit(EXIT_FAILURE);
    }
    CLEAR(*encoder);


    /****************************************************************************
     * Advanced parameter handling functions
     ****************************************************************************/

    /* These functions expose the full power of x264's preset-tune-profile system for
     * easy adjustment of large numbers //free(encoder->yuv420p_picture);of internal parameters.
     *
     * In order to replicate x264CLI's option handling, these functions MUST be called
     * in the following order:
     * 1) x264_param_default_preset
     * 2) Custom user options (via param_parse or directly assigned variables)
     * 3) x264_param_apply_fastfirstpass
     * 4) x264_param_apply_profile
     *
     * Additionally, x264CLI does not apply step 3 if the preset chosen is "placebo"
     * or --slow-firstpass is set. */
    strcpy(encoder->parameter_preset,ENCODER_PRESET);
    strcpy(encoder->parameter_tune,ENCODER_TUNE);

    encoder->x264_parameter=(x264_param_t *)malloc(sizeof(x264_param_t));
    if(!encoder->x264_parameter){
        printf("malloc x264_parameter error!\n");
        exit(EXIT_FAILURE);
    }
    CLEAR(*(encoder->x264_parameter));
    x264_param_default(encoder->x264_parameter);

    if((ret=x264_param_default_preset(encoder->x264_parameter,encoder->parameter_preset,encoder->parameter_tune))<0){
        printf("x264_param_default_preset error!\n");
        exit(EXIT_FAILURE);
    }

    encoder->x264_parameter->i_fps_den         =1;
    encoder->x264_parameter->i_fps_num         =25;
    encoder->x264_parameter->i_width       =IMAGE_WIDTH;
    encoder->x264_parameter->i_height      =IMAGE_HEIGHT;
    encoder->x264_parameter->i_threads         =1;
    encoder->x264_parameter->i_keyint_max    =25;
    encoder->x264_parameter->b_intra_refresh =1;
    encoder->x264_parameter->b_annexb      =1;

    strcpy(encoder->parameter_profile,ENCODER_PROFILE);
    if((ret=x264_param_apply_profile(encoder->x264_parameter,encoder->parameter_profile))<0){
        printf("x264_param_apply_profile error!\n");
        exit(EXIT_FAILURE);
    }

#if DEBUG
    printf("Line --------%d\n",__LINE__);
#endif

    encoder->x264_encoder=x264_encoder_open(encoder->x264_parameter);

    encoder->colorspace=ENCODER_COLORSPACE;

#if DEBUG
    printf("Line --------%d\n",__LINE__);
#endif

    encoder->yuv420p_picture=(x264_picture_t *)malloc(sizeof(x264_picture_t ));
    if(!encoder->yuv420p_picture){
        printf("malloc encoder->yuv420p_picture error!\n");
        exit(EXIT_FAILURE);
    }
    if((ret=x264_picture_alloc(encoder->yuv420p_picture,encoder->colorspace,IMAGE_WIDTH,IMAGE_HEIGHT))<0){
        printf("ret=%d\n",ret);
        printf("x264_picture_alloc error!\n");
        exit(EXIT_FAILURE);
    }

    encoder->yuv420p_picture->img.i_csp=encoder->colorspace;
    encoder->yuv420p_picture->img.i_plane=3;
    encoder->yuv420p_picture->i_type=X264_TYPE_AUTO;



#if DEBUG
    printf("Line --------%d\n",__LINE__);
#endif

    encoder->yuv=(uint8_t *)malloc(IMAGE_WIDTH*IMAGE_HEIGHT*3/2);
    if(!encoder->yuv){
        printf("malloc yuv error!\n");
        exit(EXIT_FAILURE);
    }
    CLEAR(*(encoder->yuv));

#if DEBUG
    printf("Line --------%d\n",__LINE__);
#endif

    encoder->yuv420p_picture->img.plane[0]=encoder->yuv;
    encoder->yuv420p_picture->img.plane[1]=encoder->yuv+IMAGE_WIDTH*IMAGE_HEIGHT;
    encoder->yuv420p_picture->img.plane[2]=encoder->yuv+IMAGE_WIDTH*IMAGE_HEIGHT+IMAGE_WIDTH*IMAGE_HEIGHT/4;

    if((fd_read=open(read_filename,O_RDONLY))<0){
        printf("cannot open input file!\n");
        exit(EXIT_FAILURE);
    }

    if((fd_write=open(write_filename,O_WRONLY | O_APPEND | O_CREAT,0777))<0){
        printf("cannot open output file!\n");
        exit(EXIT_FAILURE);
    }

#if DEBUG
    printf("Line --------%d\n",__LINE__);
#endif
    int n_nal;
    x264_picture_t pic_out;
    x264_nal_t *my_nal;
    encoder->nal=(x264_nal_t *)malloc(sizeof(x264_nal_t ));
    if(!encoder->nal){
        printf("malloc x264_nal_t error!\n");
        exit(EXIT_FAILURE);
    }
    CLEAR(*(encoder->nal));

    while(read(fd_read,encoder->yuv,IMAGE_WIDTH*IMAGE_HEIGHT*3/2)>0){
        encoder->yuv420p_picture->i_pts++;
        if((ret=x264_encoder_encode(encoder->x264_encoder,&encoder->nal,&n_nal,encoder->yuv420p_picture,&pic_out))<0){
            printf("x264_encoder_encode error!\n");
            exit(EXIT_FAILURE);
        }

        unsigned int length=0;
        for(my_nal=encoder->nal;my_nal<encoder->nal+n_nal;++my_nal){
            write(fd_write,my_nal->p_payload,my_nal->i_payload);
            length+=my_nal->i_payload;
        }
        printf("length=%d\n",length);
    }

    /*clean_up functions*/
    //x264_picture_clean(encoder->yuv420p_picture);
    //free(encoder->nal);//???? confused conflict with x264_encoder_close(encoder->x264_encoder);

    free(encoder->yuv);
    free(encoder->yuv420p_picture);
    free(encoder->x264_parameter);
    x264_encoder_close(encoder->x264_encoder);
    free(encoder);
    close(fd_read);
    close(fd_write);

    return 0;
}

3.        解码

利用ffmpeg进行解码

程序如下：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavutil/mathematics.h>

#define DECODED_OUTPUT_FORMAT  AV_PIX_FMT_YUV420P
#define INPUT_FILE_NAME "encode.h264"
#define OUTPUT_FILE_NAME "decode.yuv"
#define IMAGE_WIDTH  320
#define IMAGE_HEIGHT 240

void
error_handle(const char *errorInfo ){
    printf("%s error!\n",errorInfo);
    exit(EXIT_FAILURE);
}


int
main(int argc,char ** argv){
    int  write_fd,ret,videoStream;
    AVFormatContext * formatContext=NULL;
    AVCodec * codec;
    AVCodecContext * codecContext;
    AVFrame * decodedFrame;
    AVPacket packet;
    uint8_t *decodedBuffer;
    unsigned int decodedBufferSize;
    int finishedFrame;


    av_register_all();


    write_fd=open(OUTPUT_FILE_NAME,O_RDWR | O_CREAT,0666);
    if(write_fd<0){
        perror("open");
        exit(1);
    }

    ret=avformat_open_input(&formatContext, INPUT_FILE_NAME, NULL,NULL);
    if(ret<0)
        error_handle("avformat_open_input error");

    ret=avformat_find_stream_info(formatContext,NULL);
    if(ret<0)
        error_handle("av_find_stream_info");


    videoStream=0;
    codecContext=formatContext->streams[videoStream]->codec;

    codec=avcodec_find_decoder(AV_CODEC_ID_H264);
    if(codec==NULL)
        error_handle("avcodec_find_decoder error!\n");

    ret=avcodec_open2(codecContext,codec,NULL);
    if(ret<0)
        error_handle("avcodec_open2");

    decodedFrame=avcodec_alloc_frame();
    if(!decodedFrame)
        error_handle("avcodec_alloc_frame!");

    decodedBufferSize=avpicture_get_size(DECODED_OUTPUT_FORMAT,IMAGE_WIDTH,IMAGE_HEIGHT);
    decodedBuffer=(uint8_t *)malloc(decodedBufferSize);
    if(!decodedBuffer)
        error_handle("malloc decodedBuffer error!");

    av_init_packet(&packet);
    while(av_read_frame(formatContext,&packet)>=0){
            ret=avcodec_decode_video2(codecContext,decodedFrame,&finishedFrame,&packet);
            if(ret<0)
                error_handle("avcodec_decode_video2 error!");
            if(finishedFrame){
                avpicture_layout((AVPicture*)decodedFrame,DECODED_OUTPUT_FORMAT,IMAGE_WIDTH,IMAGE_HEIGHT,decodedBuffer,decodedBufferSize);
                ret=write(write_fd,decodedBuffer,decodedBufferSize);
                if(ret<0)
                    error_handle("write yuv stream error!");
            }

        av_free_packet(&packet);
    }

    while(1){
        packet.data=NULL;
        packet.size=0;
        ret=avcodec_decode_video2(codecContext,decodedFrame,&finishedFrame,&packet);
        if(ret<=0 && (finishedFrame<=0))
            break;
        if(finishedFrame){
            avpicture_layout((AVPicture*)decodedFrame,DECODED_OUTPUT_FORMAT,IMAGE_WIDTH,IMAGE_HEIGHT,decodedBuffer,decodedBufferSize);
            ret=write(write_fd,decodedBuffer,decodedBufferSize);
            if(ret<0)
                error_handle("write yuv stream error!");
        }

        av_free_packet(&packet);
    }


    avformat_close_input(&formatContext);
    free(decodedBuffer);
    av_free(decodedFrame);
    avcodec_close(codecContext);

    return 0;
}

结果：

1.      利用USB摄像头采集的YUV420P，大小11.0MB，可以用pyuv播放器正常播放。

2.      编码后的文件encode.h264，大小262.4kb，可用vlc播放器正常播放。

3.      解码后的文件decode.yuv，大小11.0MB，可以用pyuv播放器正常播放。

 

相关文件在我的资源里，里面包含：

1.      采集、编码、解码程序、对应的可执行程序和Makefile文件；

2.      Pyuv播放器（用于XP）

3.      实验文件-yuv420p.yuv 、encode.h264、 decode.yuv

4.      相关参考文档pdf版本

欢迎批评指正！

转自：http://blog.csdn.net/scalerzhangjie/article/details/8273410