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
#endif

const 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 stream
	ret = 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 decoder
	if ((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 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);

	// create and add a filter instance into an existing graph
	ret = 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 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("Can't 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;

	// add a graph described by a string to a graph
	ret = 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 graph
	ret = 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 packets
	while (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 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)
				{
					// get a frame with filtered data from sink and put it in frame
					ret = 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, 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);
						}

						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);

						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;
}