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>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 
#include 
#include 
#include 
#include 
#include 
#include 

#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_nalnal+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 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#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！