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最简单的基于FFmpeg的AVfilter例子系列文章：
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有关FFmpeg的avfilter已经写过一个水印叠加的例子《最简单的基于FFmpeg的AVfilter例子（水印叠加）》，本文作为补充再记录一个纯净版的avfilter的例子。此前libavfilter一直是结合着libavcodec等类库的接口函数使用的，因此我一直以为libavfilter库与libavcodec等类库是高度耦合的（也就是如果想使用libavfilter的视音频特效功能的话必须使用libavcodec等类库的函数）。这两天空闲的时候研究了一下libavfilter的代码后发现实际情况不是这样的：libavfilter可以独立于libavcodec等类库的接口函数作为一个“纯粹”的视音频特效类库进行使用。本文记录的“纯净版”的avfilter的例子即实现了一个纯粹的视频特效添加的功能。该例子输入为一个YUV文件，输出也是一个YUV文件，通过avfilter的功能可以处理该YUV文件实现去色调、模糊、水平翻转、裁剪、加方框、叠加文字等功能。
流程图
该程序的流程图如下所示。AVFilter的初始化比较复杂，而使用起来比较简单。初始化的时候需要调用avfilter_register_all()到avfilter_graph_config()一系列函数。而使用的时候只有两个函数：av_buffersrc_add_frame()用于向FilterGraph中加入一个AVFrame，而av_buffersink_get_frame()用于从FilterGraph中取出一个AVFrame。
avfilter_register_all()：注册所有AVFilter。
avfilter_graph_alloc()：为FilterGraph分配内存。
avfilter_graph_create_filter()：创建并向FilterGraph中添加一个Filter。
avfilter_graph_parse_ptr()：将一串通过字符串描述的Graph添加到FilterGraph中。
avfilter_graph_config()：检查FilterGraph的配置。
av_buffersrc_add_frame()：向FilterGraph中加入一个AVFrame。av_buffersink_get_frame()：从FilterGraph中取出一个AVFrame。
代码
/**
* 最简单的基于FFmpeg的AVFilter例子 - 纯净版
* Simplest FFmpeg AVfilter Example - Pure
*
* 雷霄骅 Lei Xiaohua
* [email protected]
* 中国传媒大学/数字电视技术
* Communication University of China / Digital TV Technology
* http://blog.csdn.net/leixiaohua1020
*
* 本程序使用FFmpeg的AVfilter实现了YUV像素数据的滤镜处理功能。
* 可以给YUV数据添加各种特效功能。
* 是最简单的FFmpeg的AVFilter方面的教程。
* 适合FFmpeg的初学者。
*
* This software uses FFmpeg's AVFilter to process YUV raw data.
* It can add many excellent effect to YUV data.
* It's the simplest example based on FFmpeg's AVFilter.
* Suitable for beginner of FFmpeg
*
*/
#include <stdio.h>
#define __STDC_CONSTANT_MACROS
#ifdef _WIN32
#define snprintf _snprintf
//Windows
extern "C"
{
#include "libavfilter/avfiltergraph.h"
#include "libavfilter/buffersink.h"
#include "libavfilter/buffersrc.h"
#include "libavutil/avutil.h"
#include "libavutil/imgutils.h"
};
#else
//Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include <libavfilter/avfiltergraph.h>
#include <libavfilter/buffersink.h>
#include <libavfilter/buffersrc.h>
#include <libavutil/avutil.h>
#include <libavutil/imgutils.h>
#ifdef __cplusplus
};
#endif
#endif
int main(int argc, char* argv[])
{
int ret;
AVFrame *frame_in;
AVFrame *frame_out;
unsigned char *frame_buffer_in;
unsigned char *frame_buffer_out;
AVFilterContext *buffersink_ctx;
AVFilterContext *buffersrc_ctx;
AVFilterGraph *filter_graph;
static int video_stream_index = -1;
//Input YUV
FILE *fp_in=fopen("sintel_480x272_yuv420p.yuv","rb+");
if(fp_in==NULL){
printf("Error open input file.\n");
return -1;
}
int in_width=480;
int in_height=272;
//Output YUV
FILE *fp_out=fopen("output.yuv","wb+");
if(fp_out==NULL){
printf("Error open output file.\n");
return -1;
}
//const char *filter_descr = "lutyuv='u=128:v=128'";
const char *filter_descr = "boxblur";
//const char *filter_descr = "hflip";
//const char *filter_descr = "hue='h=60:s=-3'";
//const char *filter_descr = "crop=2/3*in_w:2/3*in_h";
//const char *filter_descr = "drawbox=x=100:y=100:w=100:h=100:[email protected]";
//const char *filter_descr = "drawtext=fontfile=arial.ttf:fontcolor=green:fontsize=30:text='Lei Xiaohua'";
avfilter_register_all();
char args[512];
AVFilter *buffersrc = avfilter_get_by_name("buffer");
AVFilter *buffersink = avfilter_get_by_name("ffbuffersink");
AVFilterInOut *outputs = avfilter_inout_alloc();
AVFilterInOut *inputs = avfilter_inout_alloc();
enum PixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, PIX_FMT_NONE };
AVBufferSinkParams *buffersink_params;
filter_graph = avfilter_graph_alloc();
/* buffer video source: the decoded frames from the decoder will be inserted here. */
snprintf(args, sizeof(args),
"video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
in_width,in_height,AV_PIX_FMT_YUV420P,
1, 25,1,1);
ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
args, NULL, filter_graph);
if (ret < 0) {
printf("Cannot create buffer source\n");
return ret;
}
/* buffer video sink: to terminate the filter chain. */
buffersink_params = av_buffersink_params_alloc();
buffersink_params->pixel_fmts = pix_fmts;
ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
NULL, buffersink_params, filter_graph);
av_free(buffersink_params);
if (ret < 0) {
printf("Cannot create buffer sink\n");
return ret;
}
/* Endpoints for the filter graph. */
outputs->name = av_strdup("in");
outputs->filter_ctx = buffersrc_ctx;
outputs->pad_idx = 0;
outputs->next = NULL;
inputs->name = av_strdup("out");
inputs->filter_ctx = buffersink_ctx;
inputs->pad_idx = 0;
inputs->next = NULL;
if ((ret = avfilter_graph_parse_ptr(filter_graph, filter_descr,
&inputs, &outputs, NULL)) < 0)
return ret;
if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
return ret;
frame_in=av_frame_alloc();
frame_buffer_in=(unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, in_width,in_height,1));
av_image_fill_arrays(frame_in->data, frame_in->linesize,frame_buffer_in,
AV_PIX_FMT_YUV420P,in_width, in_height,1);
frame_out=av_frame_alloc();
frame_buffer_out=(unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, in_width,in_height,1));
av_image_fill_arrays(frame_out->data, frame_out->linesize,frame_buffer_out,
AV_PIX_FMT_YUV420P,in_width, in_height,1);
frame_in->width=in_width;
frame_in->height=in_height;
frame_in->format=AV_PIX_FMT_YUV420P;
while (1) {
if(fread(frame_buffer_in, 1, in_width*in_height*3/2, fp_in)!= in_width*in_height*3/2){
break;
}
//input Y,U,V
frame_in->data[0]=frame_buffer_in;
frame_in->data[1]=frame_buffer_in+in_width*in_height;
frame_in->data[2]=frame_buffer_in+in_width*in_height*5/4;
if (av_buffersrc_add_frame(buffersrc_ctx, frame_in) < 0) {
printf( "Error while add frame.\n");
break;
}
/* pull filtered pictures from the filtergraph */
ret = av_buffersink_get_frame(buffersink_ctx, frame_out);
if (ret < 0)
break;
//output Y,U,V
if(frame_out->format==AV_PIX_FMT_YUV420P){
for(int i=0;i<frame_out->height;i++){
fwrite(frame_out->data[0]+frame_out->linesize[0]*i,1,frame_out->width,fp_out);
}
for(int i=0;i<frame_out->height/2;i++){
fwrite(frame_out->data[1]+frame_out->linesize[1]*i,1,frame_out->width/2,fp_out);
}
for(int i=0;i<frame_out->height/2;i++){
fwrite(frame_out->data[2]+frame_out->linesize[2]*i,1,frame_out->width/2,fp_out);
}
}
printf("Process 1 frame!\n");
av_frame_unref(frame_out);
}
fclose(fp_in);
fclose(fp_out);
av_frame_free(&frame_in);
av_frame_free(&frame_out);
avfilter_graph_free(&filter_graph);
return 0;
}
结果
本程序输入为一个名称为“sintel_480x272_yuv420p.yuv”的YUV420P视频数据，输出为一个名称为“output.yuv” 的YUV420P视频数据。输入的视频数据的内容如下所示。
- lutyuv='u=128:v=128'
- boxblur
- hflip
- hue='h=60:s=-3'
- crop=2/3*in_w:2/3*in_h
- drawbox=x=100:y=100:w=100:h=100:[email protected]
- drawtext=fontfile=arial.ttf:fontcolor=green:fontsize=30:text='Lei Xiaohua'
可以通过修改程序中的filter_descr字符串实现上述几种特效。下面展示几种特效的效果图。
lutyuv='u=128:v=128'
下载
simplest ffmpeg video filter
项目主页
SourceForge：https://sourceforge.net/projects/simplestffmpegvideofilter/
Github：https://github.com/leixiaohua1020/simplest_ffmpeg_video_filter
开源中国：http://git.oschina.net/leixiaohua1020/simplest_ffmpeg_video_filter
CSDN下载地址： http://download.csdn.net/detail/leixiaohua1020/9424521
simplest_ffmpeg_video_filter：可以将一张PNG图片作为水印叠加到视频上，结合使用了libavfilter，libavcodec等类库。
simplest_ffmpeg_video_filter_pure：可以给YUV像素数据加特效，只用了libavfilter库。