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！