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Update and rename 017.README.md to 017-基于FFmpeg的AVfilter的例子-纯净版.md
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article/017-基于FFmpeg的AVfilter的例子-纯净版.md
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# 基于FFmpeg的AVfilter的例子-纯净版
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## 流程图
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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。
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流程中的关键函数如下所示：
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>avfilter_register_all()：注册所有AVFilter。<br/>
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>avfilter_graph_alloc()：为FilterGraph分配内存。<br/>
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>avfilter_graph_create_filter()：创建并向FilterGraph中添加一个Filter。<br/>
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>avfilter_graph_parse_ptr()：将一串通过字符串描述的Graph添加到FilterGraph中。<br/>
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>avfilter_graph_config()：检查FilterGraph的配置。<br/>
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>av_buffersrc_add_frame()：向FilterGraph中加入一个AVFrame。<br/>
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>av_buffersink_get_frame()：从FilterGraph中取出一个AVFrame。
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## 代码
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```C++
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/**
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* 本程序使用FFmpeg的AVfilter实现了YUV像素数据的滤镜处理功能。
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* 可以给YUV数据添加各种特效功能。
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* 是最简单的FFmpeg的AVFilter方面的教程。
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* 适合FFmpeg的初学者。
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*
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* This software uses FFmpeg's AVFilter to process YUV raw data.
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* It can add many excellent effect to YUV data.
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* It's the simplest example based on FFmpeg's AVFilter.
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* Suitable for beginner of FFmpeg
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*
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*/
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#include <stdio.h>
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#define __STDC_CONSTANT_MACROS
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#ifdef _WIN32
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#define snprintf _snprintf
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//Windows
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extern "C"
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{
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#include "libavfilter/avfiltergraph.h"
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#include "libavfilter/buffersink.h"
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#include "libavfilter/buffersrc.h"
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#include "libavutil/avutil.h"
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#include "libavutil/imgutils.h"
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};
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#else
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//Linux...
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#ifdef __cplusplus
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extern "C"
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{
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#endif
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#include <libavfilter/avfiltergraph.h>
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#include <libavfilter/buffersink.h>
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#include <libavfilter/buffersrc.h>
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#include <libavutil/avutil.h>
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#include <libavutil/imgutils.h>
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#ifdef __cplusplus
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};
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#endif
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#endif
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int main(int argc, char* argv[])
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{
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int ret;
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AVFrame *frame_in;
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AVFrame *frame_out;
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unsigned char *frame_buffer_in;
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unsigned char *frame_buffer_out;
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AVFilterContext *buffersink_ctx;
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AVFilterContext *buffersrc_ctx;
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AVFilterGraph *filter_graph;
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static int video_stream_index = -1;
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//Input YUV
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FILE *fp_in=fopen("sintel_480x272_yuv420p.yuv","rb+");
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if(fp_in==NULL){
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printf("Error open input file.\n");
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return -1;
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}
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int in_width=480;
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int in_height=272;
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//Output YUV
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FILE *fp_out=fopen("output.yuv","wb+");
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if(fp_out==NULL){
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printf("Error open output file.\n");
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return -1;
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}
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//const char *filter_descr = "lutyuv='u=128:v=128'";
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const char *filter_descr = "boxblur";
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//const char *filter_descr = "hflip";
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//const char *filter_descr = "hue='h=60:s=-3'";
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//const char *filter_descr = "crop=2/3*in_w:2/3*in_h";
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//const char *filter_descr = "drawbox=x=100:y=100:w=100:h=100:color=pink@0.5";
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//const char *filter_descr = "drawtext=fontfile=arial.ttf:fontcolor=green:fontsize=30:text='Lei Xiaohua'";
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avfilter_register_all();
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char args[512];
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AVFilter *buffersrc = avfilter_get_by_name("buffer");
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AVFilter *buffersink = avfilter_get_by_name("ffbuffersink");
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AVFilterInOut *outputs = avfilter_inout_alloc();
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AVFilterInOut *inputs = avfilter_inout_alloc();
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enum PixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, PIX_FMT_NONE };
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AVBufferSinkParams *buffersink_params;
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filter_graph = avfilter_graph_alloc();
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/* buffer video source: the decoded frames from the decoder will be inserted here. */
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snprintf(args, sizeof(args),
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"video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
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in_width,in_height,AV_PIX_FMT_YUV420P,
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1, 25,1,1);
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ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
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args, NULL, filter_graph);
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if (ret < 0) {
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printf("Cannot create buffer source\n");
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return ret;
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}
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/* buffer video sink: to terminate the filter chain. */
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buffersink_params = av_buffersink_params_alloc();
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buffersink_params->pixel_fmts = pix_fmts;
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ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
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NULL, buffersink_params, filter_graph);
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av_free(buffersink_params);
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if (ret < 0) {
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printf("Cannot create buffer sink\n");
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return ret;
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}
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/* Endpoints for the filter graph. */
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outputs->name = av_strdup("in");
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outputs->filter_ctx = buffersrc_ctx;
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outputs->pad_idx = 0;
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outputs->next = NULL;
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inputs->name = av_strdup("out");
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inputs->filter_ctx = buffersink_ctx;
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inputs->pad_idx = 0;
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inputs->next = NULL;
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if ((ret = avfilter_graph_parse_ptr(filter_graph, filter_descr,
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&inputs, &outputs, NULL)) < 0)
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return ret;
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if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
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return ret;
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frame_in=av_frame_alloc();
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frame_buffer_in=(unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, in_width,in_height,1));
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av_image_fill_arrays(frame_in->data, frame_in->linesize,frame_buffer_in,
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AV_PIX_FMT_YUV420P,in_width, in_height,1);
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frame_out=av_frame_alloc();
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frame_buffer_out=(unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, in_width,in_height,1));
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av_image_fill_arrays(frame_out->data, frame_out->linesize,frame_buffer_out,
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AV_PIX_FMT_YUV420P,in_width, in_height,1);
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frame_in->width=in_width;
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frame_in->height=in_height;
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frame_in->format=AV_PIX_FMT_YUV420P;
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while (1) {
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if(fread(frame_buffer_in, 1, in_width*in_height*3/2, fp_in)!= in_width*in_height*3/2){
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break;
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}
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//input Y,U,V
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frame_in->data[0]=frame_buffer_in;
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frame_in->data[1]=frame_buffer_in+in_width*in_height;
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frame_in->data[2]=frame_buffer_in+in_width*in_height*5/4;
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if (av_buffersrc_add_frame(buffersrc_ctx, frame_in) < 0) {
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printf( "Error while add frame.\n");
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break;
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}
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/* pull filtered pictures from the filtergraph */
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ret = av_buffersink_get_frame(buffersink_ctx, frame_out);
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if (ret < 0)
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break;
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//output Y,U,V
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if(frame_out->format==AV_PIX_FMT_YUV420P){
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for(int i=0;i<frame_out->height;i++){
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fwrite(frame_out->data[0]+frame_out->linesize[0]*i,1,frame_out->width,fp_out);
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}
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for(int i=0;i<frame_out->height/2;i++){
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fwrite(frame_out->data[1]+frame_out->linesize[1]*i,1,frame_out->width/2,fp_out);
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}
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for(int i=0;i<frame_out->height/2;i++){
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fwrite(frame_out->data[2]+frame_out->linesize[2]*i,1,frame_out->width/2,fp_out);
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}
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}
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printf("Process 1 frame!\n");
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av_frame_unref(frame_out);
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}
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fclose(fp_in);
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fclose(fp_out);
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av_frame_free(&frame_in);
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av_frame_free(&frame_out);
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avfilter_graph_free(&filter_graph);
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return 0;
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}
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```
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## 结果
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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。
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程序中提供了几种特效：
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>* lutyuv='u=128:v=128'
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>* boxblur
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>* hflip
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>* hue='h=60:s=-3'
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>* crop=2/3*in_w:2/3*in_h
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>* drawbox=x=100:y=100:w=100:h=100:color=pink@0.5
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>* drawtext=fontfile=arial.ttf:fontcolor=green:fontsize=30:text='Lei Xiaohua'
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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。
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#### lutyuv='u=128:v=128'
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#### boxblur
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#### hflip
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#### hue='h=60:s=-3'
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#### crop=2/3*in_w:2/3*in_h
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#### drawbox=x=100:y=100:w=100:h=100:color=pink@0.5
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#### drawtext=fontfile=arial.ttf:fontcolor=green:fontsize=30:text='Lei Xiaohua'
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## 下载
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Github：https://github.com/leixiaohua1020/simplest_ffmpeg_video_filter
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本程序使用包含下面两个项目：
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* 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。
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* simplest_ffmpeg_video_filter_pure：可以给YUV像素数据加特效，只用了libavfilter库。
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<br/>
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<br/>
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<br/>
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<br/>
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<br/>
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<br/>
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<br/>
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<br/>
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<br/>
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原文作者： 雷霄骅
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@@ -1 +0,0 @@
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#
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