最简单的基于 FFmpeg 的 AVfilter 例子（水印叠加）-编程知识

最简单的基于 FFmpeg 的 AVfilter 例子（水印叠加）

最简单的基于 SDL2 的音频播放器
- 正文
- 工程文件下载

参考雷霄骅博士的文章，链接：最简单的基于FFmpeg的AVfilter例子（水印叠加）

最简单的基于 SDL2 的音频播放器

正文

FFmpeg 中有一个类库：libavfilter。该类库提供了各种视音频过滤器，有很多现成的 filter 供使用，完成视频的处理很方便。

该例子完成了一个水印叠加的功能。可以将一张透明背景的 png 图片（my_logo.png）作为水印叠加到一个视频文件上。需要注意的是，其叠加工作是在解码后的 YUV 像素数据的基础上完成的。

程序支持使用 SDL1.2 显示叠加后的 YUV 数据，也可以将叠加后的 YUV 输出成文件。

SDL1.2 库的免费下载链接：SDL1.2 - from 雷霄骅.zip

流程图：

请添加图片描述

上面是一张使用 FFmpeg 的 libavfilter 的流程图。可以看出使用 libavfilter 还是需要做不少的初始化工作的。但是使用的时候还是比较简单的，就两个重要的函数：av_buffersrc_add_frame() 和 av_buffersink_get_buffer_ref()。

注：这张图中只列出了和 libavfilter 有关的函数和结构体。代码中其它函数可以参考雷霄骅博士的另一篇文章：100行代码实现最简单的基于FFMPEG+SDL的视频播放器（SDL1.x）

源代码：

// Simplest FFmpeg AVfilter Example.cpp : 定义控制台应用程序的入口点。/**
* 最简单的基于 FFmpeg 的 AVFilter 例子（叠加水印）
* Simplest FFmpeg AVfilter Example (Watermark)
*
* 源程序：
* 雷霄骅 Lei Xiaohua
* leixiaohua1020@126.com
* 中国传媒大学/数字电视技术
* Communication University of China / Digital TV Technology
* http://blog.csdn.net/leixiaohua1020
*
* 修改：
* 刘文晨 Liu Wenchen
* 812288728@qq.com
* 电子科技大学/电子信息
* University of Electronic Science and Technology of China / Electronic and Information Science
* https://blog.csdn.net/ProgramNovice
*
* 本程序使用 FFmpeg 的 AVfilter 实现了视频的水印叠加功能。
* 可以将一张 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 的初学者。
*
* 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 "stdafx.h"#include <stdio.h>
#include <stdlib.h>// 解决报错：无法解析的外部符号 __imp__fprintf，该符号在函数 _ShowError 中被引用
#pragma comment(lib, "legacy_stdio_definitions.lib")
extern "C"
{// 解决报错：无法解析的外部符号 __imp____iob_func，该符号在函数 _ShowError 中被引用FILE __iob_func[3] = { *stdin, *stdout, *stderr };
}#define __STDC_CONSTANT_MACROS
#ifdef _WIN32
// 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
#endifconst char *filter_descr = "movie=logo.png[wm];[in][wm]overlay=5:5[out]";static AVFormatContext *pFormatCtx;
static AVCodecContext *pCodecCtx;AVFilterContext *buffersrc_ctx;
AVFilterContext *buffersink_ctx;
AVFilterGraph *filter_graph;static int video_stream_index = -1;static int open_input_file(const char *filename)
{int ret = 1;AVCodec *dec;if ((ret = avformat_open_input(&pFormatCtx, filename, NULL, NULL)) < 0){printf("Can't open input file.\n");return ret;}if ((ret = avformat_find_stream_info(pFormatCtx, NULL)) < 0){printf("Can't find stream information.\n");}// select the video streamret = av_find_best_stream(pFormatCtx, AVMEDIA_TYPE_VIDEO, -1, -1, &dec, 0);if (ret < 0){printf("Can't 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 decoderif ((ret = avcodec_open2(pCodecCtx, dec, NULL)) < 0){printf("Can't open video decoder.\n");return ret;}return 0;
}// 功能：创建配置一个滤镜图，在后续滤镜处理中，可以往此滤镜图输入数据并从滤镜图获得输出数据
static int init_filters(const char *filters_descr)
{// // args 是 buffersrc 滤镜的参数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 heresnprintf(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);// create and add a filter instance into an existing graphret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",args, NULL, filter_graph);if (ret < 0){printf("Can't create buffer source.\n");return ret;}// buffer video sink: to terminate the filter chainbuffersink_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("Can't create buffer sink.\n");return ret;}// endpoints for the filter graphoutputs->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;// add a graph described by a string to a graphret = avfilter_graph_parse_ptr(filter_graph, filters_descr, &inputs, &outputs, NULL);if (ret < 0){return ret;}// check validity and configure all the links and formats in the graphret = avfilter_graph_config(filter_graph, NULL);if (ret < 0){return ret;}return 0;
}int main(int argc, char* argv[])
{int ret;AVPacket packet;AVFrame *pFrame;AVFrame *pFrame_out;int got_frame;int frame_cnt;av_register_all();avfilter_register_all();ret = open_input_file("cuc_ieschool.flv");if (ret < 0){goto end;}ret = init_filters(filter_descr);if (ret < 0){goto end;}FILE *fp_yuv = fopen("test.yuv", "wb+");// 帧计数器frame_cnt = 0;// ---------------------------- SDL 1.2 ----------------------------SDL_Surface *screen;SDL_Overlay *bmp;SDL_Rect rect;// 初始化 SDL 系统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);// ---------------------------- SDL End ----------------------------pFrame = av_frame_alloc();pFrame_out = av_frame_alloc();// read all packetswhile (1){if ((ret = av_read_frame(pFormatCtx, &packet)) < 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("Decode Error.\n");return -1;}if (got_frame){pFrame->pts = av_frame_get_best_effort_timestamp(pFrame);// push the decoded frame into the filtergraphif (av_buffersrc_add_frame(buffersrc_ctx, pFrame) < 0){printf("Error while feeding the filtergraph.\n");break;}// pull filtered pictures from the filtergraphwhile (1){// get a frame with filtered data from sink and put it in frameret = av_buffersink_get_frame(buffersink_ctx, pFrame_out);if (ret < 0){break;}printf("Process %d frame.\n", frame_cnt);if (pFrame_out->format == AV_PIX_FMT_YUV420P){// Y, U, Vfor (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);}SDL_LockYUVOverlay(bmp);int y_size = pFrame_out->width*pFrame_out->height;memcpy(bmp->pixels[0], pFrame_out->data[0], y_size); // Ymemcpy(bmp->pixels[2], pFrame_out->data[1], y_size / 4); // Umemcpy(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 40msSDL_Delay(40);frame_cnt++;}av_frame_unref(pFrame_out);}}av_frame_unref(pFrame);}av_free_packet(&packet);}fclose(fp_yuv);end:avfilter_graph_free(&filter_graph);if (pCodecCtx != NULL){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;}system("pause");return 0;
}