首先说明需要用到的ffmpeg对象，以及一些必要的字段。
ffmpeg版本：
version 4.3
所用到的头文件：
#include <libavutil/avassert.h>
#include <libavutil/opt.h>
#include <libavfilter/avfilter.h>需要的数据结构如下：
每一条输入流需要如下的字段
typedef struct Stream{
int x;
int y;
int width;
int height;
int format;//参考AVPixelFormat
AVFilterContext* buffersrc_ctx;
AVFilter* buffersrc;
AVFilterInOut* output;
AVFrame* inputFrame;
} Stream;输出流需要如下字段
typedef struct Merge {
AVFilterGraph* filter_graph;
AVFilterContext* buffersink_ctx;
AVFilter* buffersink;
AVFilterInOut* input;
const char* filters_descr;
AVFrame* outputFrame;
unsigned char* outputBuffer;
int outputWidth;
int outputHeight;
int outputFormat;//参考AVPixelFormat
Stream *streams[128];
int streamCount;
} Merge;主要流程如下：
1、构造输出流及输入流
构造输出流，输出流需要设置分辨率以及输出的像素格式
Merge* Merge_Create(int outputWidth, int outputHeight, int outputFormat) {
Merge* merge = malloc(sizeof(Merge));
memset(merge, 0, sizeof(Merge));
merge->outputWidth = outputWidth;
merge->outputHeight = outputHeight;
merge->outputFormat = outputFormat;
return merge;
}添加输入流，输入流需要设置在输出流中的位置和大小，以及输入流像素格式
Stream* Merge_AddStream(Merge* merge, int x, int y, int width, int height, int format) {
Stream* stream = malloc(sizeof(Stream));
memset(merge, 0, sizeof(Stream));
stream->x = x;
stream->y = y;
stream->width = width;
stream->height = height;
stream->format = format;
merge->streams[merge->streamCount++] = stream;
return stream;
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2、初始化滤镜
主要用到的滤镜是filters_descr = "[in0]pad=1280:640:0:0:black[x0];[x0][in1]overlay=640:0[x1];[x1][in2]overlay=600:0[x2];[x2]null[out]";
//初始化Merge
int Merge_Init(Merge* merge) {
char args[512];
char name[8];
char* filters_descr = NULL;
int ret;
//avfilter_register_all();//旧版可能用到此行
merge->buffersink = avfilter_get_by_name("buffersink");
av_assert0(merge->buffersink);
merge->input = avfilter_inout_alloc();
if (merge->input == NULL)
{
printf("alloc inout fail\n");
goto fail;
}
merge->filter_graph = avfilter_graph_alloc();
if (merge->input == NULL)
{
printf("alloc graph fail\n");
goto fail;
}
ret = avfilter_graph_create_filter(&merge->buffersink_ctx, merge->buffersink, "out", NULL, NULL, merge->filter_graph);
if (ret < 0)
{
printf("graph create fail\n");
goto fail;
}
merge->input->name = av_strdup("out");
merge->input->filter_ctx = merge->buffersink_ctx;
merge->input->pad_idx = 0;
merge->input->next = NULL;
merge->outputFrame = av_frame_alloc();
if (merge->outputFrame == NULL)
{
printf("alloc frame fail\n");
goto fail;
}
merge->outputBuffer = (unsigned char*)av_malloc(av_image_get_buffer_size(merge->outputFormat, merge->outputWidth, merge->outputHeight, 1));
if (merge->outputBuffer == NULL)
{
printf("alloc buffer fail\n");
goto fail;
}
enum AVPixelFormat pix_fmts[2] = { 0, AV_PIX_FMT_NONE };
pix_fmts[0] = merge->outputFormat;
ret = av_opt_set_int_list(merge->buffersink_ctx, "pix_fmts", pix_fmts, AV_PIX_FMT_NONE, AV_OPT_SEARCH_CHILDREN);
if (ret < 0) {
printf("set opt fail\n");
goto fail;
}
Stream** streams = merge->streams;
for (int i = 0; i < merge->streamCount; i++)
{
streams[i]->buffersrc = avfilter_get_by_name("buffer");
av_assert0(streams[i]->buffersrc);
snprintf(args, sizeof(args), "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d", streams[i]->width, streams[i]->height, streams[i]->format, 1, 90000, 1, 1);
snprintf(name, sizeof(name), "in%d", i);
ret = avfilter_graph_create_filter(&streams[i]->buffersrc_ctx, streams[i]->buffersrc, name, args, NULL, merge->filter_graph);
if (ret < 0)
{
printf("stream graph create fail\n");
goto fail;
}
streams[i]->output = avfilter_inout_alloc();
streams[i]->output->name = av_strdup(name);
streams[i]->output->filter_ctx = streams[i]->buffersrc_ctx;
streams[i]->output->pad_idx = 0;
streams[i]->output->next = NULL;
streams[i]->inputFrame = av_frame_alloc();
if (streams[i]->inputFrame == NULL)
{
printf("alloc frame fail\n");
goto fail;
}
streams[i]->inputFrame->format = streams[i]->format;
streams[i]->inputFrame->width = streams[i]->width;
streams[i]->inputFrame->height = streams[i]->height;
if (i > 0)
{
streams[i - 1]->output->next = streams[i]->output;
}
}
/*filters_descr = "[in0]pad=1280:640:0:0:black[x0];[x0][in1]overlay=640:0[x1];[x1][in2]overlay=600:0[x2];[x2]null[out]";*/
filters_descr = malloc(sizeof(char) * merge->streamCount * 128);
if (filters_descr == NULL)
{
printf("alloc string fail\n");
goto fail;
}
char sigle_descr[128];
snprintf(sigle_descr, sizeof(sigle_descr), "[in0]pad=%d:%d:%d:%d:black[x0];", merge->outputWidth, merge->outputHeight, streams[0]->x, streams[0]->y);
strcpy(filters_descr, sigle_descr);
int i = 1;
for (; i < merge->streamCount; i++)
{
snprintf(sigle_descr, sizeof(sigle_descr), "[x%d][in%d]overlay=%d:%d[x%d];", i - 1, i, streams[i]->x, streams[i]->y, i);
strcat(filters_descr, sigle_descr);
}
snprintf(sigle_descr, sizeof(sigle_descr), "[x%d]null[out]", i - 1);
strcat(filters_descr, sigle_descr);
ret = avfilter_graph_parse_ptr(merge->filter_graph, filters_descr, &merge->input, &streams[0]->output, NULL);
if (ret < 0)
{
printf("graph parse fail\n");
goto fail;
}
// 过滤配置初始化
ret = avfilter_graph_config(merge->filter_graph, NULL);
if (ret < 0)
{
printf("graph config fail\n");
goto fail;
}
if (filters_descr != NULL)
free(filters_descr);
return 0;
fail:
if (filters_descr != NULL)
free(filters_descr);
Merge_Deinit(merge); //执行反初始化
return -1;
}3、写输入流
void Merge_WriteStream(Merge* merge, Stream* stream, const unsigned char* buffer, int timestamp) {
av_image_fill_arrays(stream->inputFrame->data, stream->inputFrame->linesize, buffer, stream->format, stream->width, stream->height, 1);
stream->inputFrame->pts = timestamp;
if (av_buffersrc_write_frame(stream->buffersrc_ctx, stream->inputFrame) < 0) {
printf("Error while add frame.\n");
}
}4、合并流
调用下列方法，即可得到合并后的一帧的数据。可以按照一定帧率调用3、4方法。
const unsigned char* Merge_Merge(Merge* merge) {
int ret = av_buffersink_get_frame(merge->buffersink_ctx, merge->outputFrame);
if (ret < 0) {
printf("Error while get frame.\n");
return NULL;
}
av_image_copy_to_buffer(merge->outputBuffer,
av_image_get_buffer_size(merge->outputFormat, merge->outputWidth, merge->outputHeight, 1),
merge->outputFrame->data, merge->outputFrame->linesize, merge->outputFrame->format, merge->outputFrame->width, merge->outputFrame->height, 1);
av_frame_unref(merge->outputFrame);
return merge->outputBuffer;
}5、结束，反初始化，销毁对象
static void Merge_Deinit(Merge* merge)
{
if (merge->input != NULL)
avfilter_inout_free(&merge->input);
if (merge->filter_graph != NULL)
avfilter_graph_free(&merge->filter_graph);
if (merge->outputFrame != NULL)
av_frame_free(&merge->outputFrame);
if (merge->outputBuffer != NULL)
av_free(merge->outputBuffer);
for (int i = 0; i < merge->streamCount; i++)
{
Stream* stream = merge->streams[i];
if (stream->inputFrame != NULL)
av_frame_free(&stream->inputFrame);
free(stream);
}
merge->streamCount = 0;
}void Merge_Destroy(Merge* merge) {
Merge_Deinit(merge);
free(merge);
}调用流程示例：
int main() {
int flag = 1;
Merge* merge = Merge_Create(1920, 1080, 0);
Stream* stream1 = Merge_AddStream(merge, 0, 0, 960, 540, 0);
Stream* stream2 = Merge_AddStream(merge, 960, 540, 960, 540, 0);
Stream* stream3 = Merge_AddStream(merge, 0, 540, 960, 540, 0);
if (Merge_Init(merge) != 0)
{
Merge_Destroy(merge);
return -1;
}
while (flag)
{
clock_t time = clock();
unsigned char* buffer1;
unsigned char* buffer2;
unsigned char* buffer3;
//获取每路流的数据
...
//获取每路流的数据-end
Merge_WriteStream(merge, stream1, buffer1, time);
Merge_WriteStream(merge, stream2, buffer2, time);
Merge_WriteStream(merge, stream3, buffer3, time);
unsigned char* mergedBuffer = Merge_Merge(merge);
//显示或编码推流
...
//显示或编码推流-end
}
Merge_Destroy(merge);
}需要注意的是上述方法最好在单线程中使用，多线程使用可能需要另外做修改。
效果如下
原文链接：使用ffmepg实现多路视频流合并 - 资料 - 我爱音视频网 - 构建全国最权威的音视频技术交流分享论坛
本文福利，免费领取C++音视频学习提升资料，内容包括（C/C++，Linux 服务器开发，面试题，FFmpeg ，webRTC ，rtmp ，hls ，rtsp ，ffplay ，srs）↓↓↓↓↓↓文章底部↓↓↓↓见下面