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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

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。

image

流程中的关键函数如下所示：

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

/** 
 * 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:color=pink@0.5";
	//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。

image

程序中提供了几种特效：

  • lutyuv='u=128:v=128'
  • boxblur
  • hflip
  • hue='h=60:s=-3'
  • crop=2/3in_w:2/3in_h
  • drawbox=x=100:y=100:w=100:h=100:color=pink@0.5
  • 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'

image

boxblur

image

hflip

image

hue='h=60:s=-3'

image

crop=2/3in_w:2/3in_h

image

drawbox=x=100:y=100:w=100:h=100:color=pink@0.5

image

drawtext=fontfile=arial.ttf:fontcolor=green:fontsize=30:text='Lei Xiaohua'

image

下载

Github：https://github.com/leixiaohua1020/simplest_ffmpeg_video_filter

本程序使用包含下面两个项目：

  • 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。









原文作者： 雷霄骅