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最简单的基于FFmpeg的AVfilter样例系列文章：
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FFMPEG中有一个类库：libavfilter。该类库提供了各种视音频过滤器。
之前一直没有怎么使用过这个类库，近期看了一下它的使用说明，发现还是非常强大的，有非常多现成的filter供使用，完毕视频的处理非常方便。在此将它的一个样例基础上完毕了一个水印叠加器。而且移植到了VC2010下，方便开发者学习研究它的用法。
该样例完毕了一个水印叠加的功能。能够将一张透明背景的PNG图片作为水印叠加到一个视频文件上。须要注意的是，其叠加工作是在解码后的YUV像素数据的基础上完毕的。程序支持使用SDL显示叠加后的YUV数据。
也能够将叠加后的YUV输出成文件。
流程图
以下附一张使用FFmpeg的libavfilter的流程图。能够看出使用libavfilter还是须要做不少的初始化工作的。可是使用的时候还是比較简单的。就两个重要的函数：av_buffersrc_add_frame()和av_buffersink_get_buffer_ref()。
PS：这张图中仅仅列出了和libavfilter有关的函数和结构体。
代码中其他函数能够參考：100行代码实现最简单的基于FFMPEG+SDL的视频播放器（SDL1.x）
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代码
以下直接贴上代码：
/**
* 最简单的基于FFmpeg的AVFilter样例（叠加水印）
* Simplest FFmpeg AVfilter Example (Watermark)
*
* 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实现了视频的水印叠加功能。
* 能够将一张PNG图片作为水印叠加到视频上。 * 是最简单的FFmpeg的AVFilter方面的教程。
* 适合FFmpeg的刚開始学习的人。
*
* This software uses FFmpeg's AVFilter to add watermark in a video file.
* It can add a PNG format picture as watermark to a video file.
* 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 "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libavfilter/avfiltergraph.h"
#include "libavfilter/buffersink.h"
#include "libavfilter/buffersrc.h"
#include "libavutil/avutil.h"
#include "libswscale/swscale.h"
#include "SDL/SDL.h"
};
#else
//Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavfilter/avfiltergraph.h>
#include <libavfilter/buffersink.h>
#include <libavfilter/buffersrc.h>
#include <libavutil/avutil.h>
#include <libswscale/swscale.h>
#include <SDL/SDL.h>
#ifdef __cplusplus
};
#endif
#endif //Enable SDL?
#define ENABLE_SDL 1
//Output YUV data?
#define ENABLE_YUVFILE 1 const char *filter_descr = "movie=my_logo.png[wm];[in][wm]overlay=5:5[out]"; static AVFormatContext *pFormatCtx;
static AVCodecContext *pCodecCtx;
AVFilterContext *buffersink_ctx;
AVFilterContext *buffersrc_ctx;
AVFilterGraph *filter_graph;
static int video_stream_index = -1; static int open_input_file(const char *filename)
{
int ret;
AVCodec *dec; if ((ret = avformat_open_input(&pFormatCtx, filename, NULL, NULL)) < 0) {
printf( "Cannot open input file\n");
return ret;
} if ((ret = avformat_find_stream_info(pFormatCtx, NULL)) < 0) {
printf( "Cannot find stream information\n");
return ret;
} /* select the video stream */
ret = av_find_best_stream(pFormatCtx, AVMEDIA_TYPE_VIDEO, -1, -1, &dec, 0);
if (ret < 0) {
printf( "Cannot find a video stream in the input file\n");
return ret;
}
video_stream_index = ret;
pCodecCtx = pFormatCtx->streams[video_stream_index]->codec; /* init the video decoder */
if ((ret = avcodec_open2(pCodecCtx, dec, NULL)) < 0) {
printf( "Cannot open video decoder\n");
return ret;
} return 0;
} static int init_filters(const char *filters_descr)
{
char args[512];
int ret;
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 AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_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",
pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
pCodecCtx->time_base.num, pCodecCtx->time_base.den,
pCodecCtx->sample_aspect_ratio.num, pCodecCtx->sample_aspect_ratio.den); 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, filters_descr,
&inputs, &outputs, NULL)) < 0)
return ret; if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
return ret;
return 0;
} int main(int argc, char* argv[])
{
int ret;
AVPacket packet;
AVFrame *pFrame;
AVFrame *pFrame_out; int got_frame; av_register_all();
avfilter_register_all(); if ((ret = open_input_file("cuc_ieschool.flv")) < 0)
goto end;
if ((ret = init_filters(filter_descr)) < 0)
goto end; #if ENABLE_YUVFILE
FILE *fp_yuv=fopen("test.yuv","wb+");
#endif
#if ENABLE_SDL
SDL_Surface *screen;
SDL_Overlay *bmp;
SDL_Rect rect;
if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
printf( "Could not initialize SDL - %s\n", SDL_GetError());
return -1;
}
screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 0, 0);
if(!screen) {
printf("SDL: could not set video mode - exiting\n");
return -1;
}
bmp = SDL_CreateYUVOverlay(pCodecCtx->width, pCodecCtx->height,SDL_YV12_OVERLAY, screen); SDL_WM_SetCaption("Simplest FFmpeg Video Filter",NULL);
#endif pFrame=av_frame_alloc();
pFrame_out=av_frame_alloc(); /* read all packets */
while (1) { ret = av_read_frame(pFormatCtx, &packet);
if (ret< 0)
break; if (packet.stream_index == video_stream_index) {
got_frame = 0;
ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_frame, &packet);
if (ret < 0) {
printf( "Error decoding video\n");
break;
} if (got_frame) {
pFrame->pts = av_frame_get_best_effort_timestamp(pFrame); /* push the decoded frame into the filtergraph */
if (av_buffersrc_add_frame(buffersrc_ctx, pFrame) < 0) {
printf( "Error while feeding the filtergraph\n");
break;
} /* pull filtered pictures from the filtergraph */
while (1) { ret = av_buffersink_get_frame(buffersink_ctx, pFrame_out);
if (ret < 0)
break; printf("Process 1 frame!\n"); if (pFrame_out->format==AV_PIX_FMT_YUV420P) {
#if ENABLE_YUVFILE
//Y, U, V
for(int i=0;i<pFrame_out->height;i++){
fwrite(pFrame_out->data[0]+pFrame_out->linesize[0]*i,1,pFrame_out->width,fp_yuv);
}
for(int i=0;i<pFrame_out->height/2;i++){
fwrite(pFrame_out->data[1]+pFrame_out->linesize[1]*i,1,pFrame_out->width/2,fp_yuv);
}
for(int i=0;i<pFrame_out->height/2;i++){
fwrite(pFrame_out->data[2]+pFrame_out->linesize[2]*i,1,pFrame_out->width/2,fp_yuv);
}
#endif #if ENABLE_SDL
SDL_LockYUVOverlay(bmp);
int y_size=pFrame_out->width*pFrame_out->height;
memcpy(bmp->pixels[0],pFrame_out->data[0],y_size); //Y
memcpy(bmp->pixels[2],pFrame_out->data[1],y_size/4); //U
memcpy(bmp->pixels[1],pFrame_out->data[2],y_size/4); //V
bmp->pitches[0]=pFrame_out->linesize[0];
bmp->pitches[2]=pFrame_out->linesize[1];
bmp->pitches[1]=pFrame_out->linesize[2];
SDL_UnlockYUVOverlay(bmp);
rect.x = 0;
rect.y = 0;
rect.w = pFrame_out->width;
rect.h = pFrame_out->height;
SDL_DisplayYUVOverlay(bmp, &rect);
//Delay 40ms
SDL_Delay(40);
#endif
}
av_frame_unref(pFrame_out);
}
}
av_frame_unref(pFrame);
}
av_free_packet(&packet);
}
#if ENABLE_YUVFILE
fclose(fp_yuv);
#endif end:
avfilter_graph_free(&filter_graph);
if (pCodecCtx)
avcodec_close(pCodecCtx);
avformat_close_input(&pFormatCtx); if (ret < 0 && ret != AVERROR_EOF) {
char buf[1024];
av_strerror(ret, buf, sizeof(buf));
printf("Error occurred: %s\n", buf);
return -1;
} return 0;
}
结果
程序的执行效果如图所看到的。
须要叠加的水印为一张PNG（透明）图片（在这里是my_logo.png）。
须要叠加的视频为一个普通的FLV格式的视频（在这里是cuc_ieschool.flv）。
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程序执行的时候，会通过SDL显示水印叠加的结果，如图所看到的。此外。也能够将水印叠加后的解码数据输出成文件。
注：SDL显示和输出YUV能够通过程序最前面的宏控制：
#define ENABLE_SDL 1
#define ENABLE_YUVFILE 1
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输出的YUV文件如图所看到的。
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/leixiaohua1020/7465861
[一个小错误]
注：因为失误，CSDN上的项目少了一个SDL.dll文件，去SDL官网
http://www.libsdl.org/download-1.2.php
下载一个Runtime Libraries就可以
PUDN下载地址（修复了SDL问题）：
http://www.pudn.com/downloads644/sourcecode/multimedia/detail2605264.html
SourceForge上已经修正该问题。
更新-1.1 (2015.2.13)=========================================
这次考虑到了跨平台的要求，调整了源码。经过这次调整之后，源码能够在以下平台编译通过：
::VS2010 Environment
call "D:\Program Files\Microsoft Visual Studio 10.0\VC\vcvarsall.bat"
::include
@set INCLUDE=include;%INCLUDE%
::lib
@set LIB=lib;%LIB%
::compile and link
cl simplest_ffmpeg_video_filter.cpp /MD /link SDL.lib SDLmain.lib avcodec.lib ^
avformat.lib avutil.lib avdevice.lib avfilter.lib postproc.lib swresample.lib swscale.lib ^
/SUBSYSTEM:WINDOWS /OPT:NOREF
g++ simplest_ffmpeg_video_filter.cpp -g -o simplest_ffmpeg_video_filter.exe \
-I /usr/local/include -L /usr/local/lib \
-lmingw32 -lSDLmain -lSDL -lavformat -lavcodec -lavutil -lavfilter -lswscale
gcc simplest_ffmpeg_video_filter.cpp -g -o simplest_ffmpeg_video_filter.out \
-I /usr/local/include -L /usr/local/lib \
-lSDLmain -lSDL -lavformat -lavcodec -lavutil -lavfilter -lswscale
gcc simplest_ffmpeg_video_filter.cpp -g -o simplest_ffmpeg_video_filter.out \
-framework Cocoa -I /usr/local/include -L /usr/local/lib \
-lSDLmain -lSDL -lavformat -lavcodec -lavutil -lavfilter -lswscale
PS：相关的编译命令已经保存到了工程目录中
CSDN下载地址：http://download.csdn.net/detail/leixiaohua1020/8445551
SourceForge上已经更新。
更新-1.2 (2016.2.1)=========================================
新增了“最简单的基于FFmpeg的avfilter的样例-纯净版”工程