前面一篇博客介绍在centos上搭建点击打开链接ffmpeg及x264开发环境。以下就来问个样例：
1、利用x264库将YUV格式视频文件编码为h264格式视频文件
2、利用ffmpeh库将h264格式的视频文件解码为yuv格式视频文件
解码和编码前后对文件大小进行比較，如图：
当中yuv420p.yuv为原始文件，大小77M
encode.h264为H264编码后的视频文件，大小1.4M
decode.yuv为ffmpeg解码后的视频文件，大小77M。
从文件的大小非常明显能够看出h264压缩率。在Ｗｉｎｄｏｗｓ平台分辨播放了三个文件，画面看不出差别。
以下是代码＂
/*File : yuvTO264.c
*Auth : sjin
*Date : 20141115
*Mail : 413977243@qq.com
*/
/*利用x264库将YUV文件编码为h264文件
*
*/
#include <stdint.h>
#include <x264.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#define CLEAR(x) (memset((&x),0,sizeof(x)))
#define IMAGE_WIDTH 176
#define IMAGE_HEIGHT 144
#define ENCODER_PRESET "veryfast"
/*配置參数
* 使用默认參数，在这里使用了zerolatency的选项，使用这个选项之后，就不会有
* delayed_frames，假设你使用不是这个的话，还须要在编码完毕之后得到缓存的
* 编码帧
*/
#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 !
");
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!
");
exit(EXIT_FAILURE);
}
/*初始化编码器*/
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!
");
exit(EXIT_FAILURE);
}
/*cpuFlags 去空缓冲区继续使用不死锁保证*/
encoder->x264_parameter->i_threads =X264_SYNC_LOOKAHEAD_AUTO;
/*视频选项*/
encoder->x264_parameter->i_width =IMAGE_WIDTH;//要编码的图像的宽度
encoder->x264_parameter->i_height =IMAGE_HEIGHT;//要编码的图像的高度
encoder->x264_parameter->i_frame_total =0;//要编码的总帧数，不知道用0
encoder->x264_parameter->i_keyint_max =25;
/*流參数*/
encoder->x264_parameter->i_bframe =5;
encoder->x264_parameter->b_open_gop =0;
encoder->x264_parameter->i_bframe_pyramid=0;
encoder->x264_parameter->i_bframe_adaptive=X264_B_ADAPT_TRELLIS;
/*log參数，不须要打印编码信息时直接凝视掉*/
encoder->x264_parameter->i_log_level =X264_LOG_DEBUG;
encoder->x264_parameter->i_fps_den =1;//码率分母
encoder->x264_parameter->i_fps_num =25;//码率分子
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!
");
exit(EXIT_FAILURE);
}
/*打开编码器*/
encoder->x264_encoder = x264_encoder_open(encoder->x264_parameter);
encoder->colorspace = ENCODER_COLORSPACE;
/*初始化pic*/
encoder->yuv420p_picture = (x264_picture_t *)malloc(sizeof(x264_picture_t ));
if(!encoder->yuv420p_picture){
printf("malloc encoder->yuv420p_picture error!
");
exit(EXIT_FAILURE);
}
if((ret = x264_picture_alloc(encoder->yuv420p_picture,encoder->colorspace,IMAGE_WIDTH,IMAGE_HEIGHT))<0){
printf("ret=%d
",ret);
printf("x264_picture_alloc error!
");
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;
/*申请YUV buffer*/
encoder->yuv = (uint8_t *)malloc(IMAGE_WIDTH*IMAGE_HEIGHT*3/2);
if(!encoder->yuv){
printf("malloc yuv error!
");
exit(EXIT_FAILURE);
}
CLEAR(*(encoder->yuv));
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!
");
exit(EXIT_FAILURE);
}
if((fd_write = open(write_filename,O_WRONLY | O_APPEND | O_CREAT,0777))<0){
printf("cannot open output file!
");
exit(EXIT_FAILURE);
}
int n_nal = 0;
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!
");
exit(EXIT_FAILURE);
}
CLEAR(*(encoder->nal));
/*编码*/
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!
");
exit(EXIT_FAILURE);
}
for(my_nal = encoder->nal; my_nal<encoder->nal+n_nal; ++my_nal){
write(fd_write,my_nal->p_payload,my_nal->i_payload);
}
}
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;
}
/*File : decode_h264.c
*Auth : sjin
*Date : 20141115
*Mail : 413977243@qq.com
*/
/*将h264解码为yuv文件*/
#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"
/*h264文件的宽度和高度，必须和实际的宽度和高度一致
*否则将出错
* */
#define IMAGE_WIDTH 176
#define IMAGE_HEIGHT 144
void error_handle(const char *errorInfo )
{
printf("%s error!
",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;
//初始化环境
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");
//打印输入文件的具体信息
av_dump_format(formatContext,0,INPUT_FILE_NAME,0);
videoStream = 0;
codecContext = formatContext->streams[videoStream]->codec;
codec = avcodec_find_decoder(AV_CODEC_ID_H264);
if(codec == NULL)
error_handle("avcodec_find_decoder error!
");
ret = avcodec_open2(codecContext,codec,NULL);
if(ret<0)
error_handle("avcodec_open2");
//分配保存视频帧的空间
decodedFrame = avcodec_alloc_frame();
if(!decodedFrame)
error_handle("avcodec_alloc_frame!");
//分配解码后视频帧的空间
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);
}
/*防止视频解码完毕后丢帧的情况*/
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;
}
Makefile:
# use pkg-config for getting CFLAGS and LDLIBS
FFMPEG_LIBS= libavdevice
libavformat
libavfilter
libavcodec
libswresample
libswscale
libavutil
CFLAGS += -Wall -O2 -g
CFLAGS := $(shell pkg-config --cflags $(FFMPEG_LIBS)) $(CFLAGS)
LDLIBS := $(shell pkg-config --libs $(FFMPEG_LIBS)) $(LDLIBS)
EXAMPLES= decode_h264 yuvTO264
OBJS=$(addsuffix .o,$(EXAMPLES))
# the following examples make explicit use of the math library
LDLIBS += -lx264 -m32 -pthread -lm -ldl
.phony:all clean
all: $(OBJS) $(EXAMPLES)
clean:
rm $(EXAMPLES) $(OBJS)
參考资料：
參考资料
1、http://blog.csdn.net/liushu1231/article/details/9203239
2、http://www.cnblogs.com/fojian/archive/2012/09/01/2666627.html
3、http://stackoverflow.com/questions/2940671/how-does-one-encode-a-series-of-images-into-h264-using-the-x264-c-api
4、http://blog.yikuyiku.com/?p=3486
1、http://blog.csdn.net/liushu1231/article/details/9203239
2、http://www.cnblogs.com/fojian/archive/2012/09/01/2666627.html
3、http://stackoverflow.com/questions/2940671/how-does-one-encode-a-series-of-images-into-h264-using-the-x264-c-api
4、http://blog.yikuyiku.com/?p=3486