"rtsp_" + to_string(i+1)

这段代码可能是在将整型变量 i+1 转换成字符串，并将其附加到另一个字符串 "rtsp_" 后面。具体来说，"to_string" 是 C++11 中新增的一个函数，用于将数字转换成字符串。例如，to_string(123) 将返回字符串 "123"。在这里，i+1 表示一个摄像头的编号，加 1 是因为数组下标从 0 开始。"rtsp_" 是一个字符串，表示每个摄像头的 RTSP 地址的前缀。因此，"rtsp_" + to_string(i+1) 将返回一个字符串，表示第 i+1 个摄像头的 RTSP 地址。

相关问题

c++ffmpeg+rtsp

C++结合FFmpeg可以实现对RTSP流的拉取和处理。下面是一个使用C++和FFmpeg的示例代码，用于拉取RTSP流并将其保存为本地文件：

#include <iostream>
#include <fstream>
#include <string>
#include <thread>
#include <chrono>

extern "C" {
#include <libavformat/avformat.h>
}

int main() {
    // 初始化FFmpeg库
    av_register_all();

    // 创建AVFormatContext对象
    AVFormatContext* formatContext = avformat_alloc_context();

    // 设置RTSP地址
    std::string rtspUrl = "rtsp://example.com/stream";

    // 打开RTSP流
    if (avformat_open_input(&formatContext, rtspUrl.c_str(), nullptr, nullptr) != 0) {
        std::cerr << "无法打开RTSP流" << std::endl;        return -1;
    }

    // 查找流信息
    if (avformat_find_stream_info(formatContext, nullptr) < 0) {
        std::cerr << "无法获取流信息" << std::endl;
        return -1;
    }

    // 找到视频流索引
    int videoStreamIndex = -1;
    for (unsigned int i = 0; i < formatContext->nb_streams; i++) {
        if (formatContext->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoStreamIndex = i;
            break;
        }
    }

    // 检查是否找到视频流
    if (videoStreamIndex == -1) {
        std::cerr << "未找到视频流" << std::endl;
        return -1;
    }

    // 获取视频流的解码器参数
    AVCodecParameters* codecParameters = formatContext->streams[videoStreamIndex]->codecpar;

    // 查找视频流的解码器
    AVCodec* codec = avcodec_find_decoder(codecParameters->codec_id);
    if (codec == nullptr) {
        std::cerr << "未找到解码器" << std::endl;
        return -1;
    }

    // 创建解码器上下文
    AVCodecContext* codecContext = avcodec_alloc_context3(codec);
    if (codecContext == nullptr) {
        std::cerr << "无法创建解码器上下文" << std::endl;
        return -1;
    }

    // 将解码器参数复制到解码器上下文
    if (avcodec_parameters_to_context(codecContext, codecParameters) < 0) {
        std::cerr << "无法复制解码器参数到解码器上下文" << std::endl;
        return -1;
    }

    // 打开解码器
    if (avcodec_open2(codecContext, codec, nullptr) < 0) {
        std::cerr << "无法打开解码器" << std::endl;
        return -1;
    }

    // 创建AVPacket对象
    AVPacket* packet = av_packet_alloc();

    // 创建AVFrame对象
    AVFrame* frame = av_frame_alloc();

    // 创建输出文件
    std::ofstream outputFile("output.yuv", std::ios::binary);

    // 读取并保存视频帧
    while (av_read_frame(formatContext, packet) >= 0) {
        // 检查是否为视频流
        if (packet->stream_index == videoStreamIndex) {
            // 解码视频帧
            avcodec_send_packet(codecContext, packet);
            while (avcodec_receive_frame(codecContext, frame) == 0) {
                // 将YUV数据写入文件
                for (int y = 0; y < frame->height; y++) {
                    outputFile.write(reinterpret_cast<char*>(frame->data[0] + y * frame->linesize[0]), frame->width);
                }
                for (int y = 0; y < frame->height / 2; y++) {
                    outputFile.write(reinterpret_cast<char*>(frame->data[1] + y * frame->linesize[1]), frame->width / 2);
                    outputFile.write(reinterpret_cast<char*>(frame->data[2] + y * frame->linesize[2]), frame->width / 2);
                }
            }
        }

        // 释放AVPacket对象
        av_packet_unref(packet);

        // 暂停一段时间，模拟实时处理
        std::this_thread::sleep_for(std::chrono::milliseconds(10));
    }

    // 释放AVFrame对象
    av_frame_free(&frame);

    // 释放AVPacket对象
    av_packet_free(&packet);

    // 关闭解码器
    avcodec_close(codecContext);

    // 释放解码器上下文
    avcodec_free_context(&codecContext);

    // 关闭输入流
    avformat_close_input(&formatContext);

    // 释放AVFormatContext对象
    avformat_free_context(formatContext);

    // 关闭输出文件
    outputFile.close();

    return 0;
}

这段代码使用FFmpeg库打开RTSP流，查找视频流并解码视频帧，然后将YUV数据保存到本地文件中。你可以根据自己的需求进行修改和扩展。

c++用ffmpeg创建rtsp服务器

要使用 C++ 和 FFmpeg 创建 RTSP 服务器，你需要了解以下几个步骤：

1. 安装 FFmpeg 库：你需要从 FFmpeg 官网下载源代码，并按照说明进行编译和安装。

2. 创建 RTSP 服务器：你需要编写一个 C++ 程序来创建 RTSP 服务器。可以使用 Live555 或者 FFmpeg 提供的库来完成这个任务。如果你选择使用 FFmpeg，你需要使用下面的代码来创建 RTSP 服务器：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <pthread.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <fcntl.h>
#include <stdbool.h>
#include <libavutil/avutil.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libavutil/opt.h>
#include <libavutil/error.h>
#include <libavutil/time.h>
#include <libavutil/mathematics.h>
#include <libswscale/swscale.h>
#include <libswresample/swresample.h>
#include <libavutil/imgutils.h>

#define RTSP_PORT   554
#define MAX_CLIENTS 10

typedef struct RTSPClient {
    int state;
    int socket;
    struct sockaddr_in address;
    AVFormatContext *pFormatCtx;
    AVCodecContext *pCodecCtx;
    AVCodec *pCodec;
    AVFrame *pFrame;
    AVPacket packet;
    struct SwsContext *img_convert_ctx;
    int video_stream_index;
    pthread_t thread_id;
    bool is_running;
} RTSPClient;

RTSPClient clients[MAX_CLIENTS];

void* client_thread(void *arg) {
    RTSPClient *client = (RTSPClient*)arg;
    int ret;
    AVPacket packet;
    AVFrame *frame;
    uint8_t *buffer;
    int buffer_size;
    struct timeval tv;
    int64_t start_time, end_time, pts;
    int64_t duration, sleep_time;
    int64_t last_frame_pts = -1;

    client->is_running = true;

    while (client->is_running) {
        ret = av_read_frame(client->pFormatCtx, &packet);
        if (ret < 0) {
            if (ret == AVERROR_EOF) {
                printf("End of stream\n");
                break;
            } else if (ret == AVERROR(EAGAIN)) {
                usleep(1000);
                continue;
            } else {
                char errbuf[AV_ERROR_MAX_STRING_SIZE];
                av_make_error_string(errbuf, AV_ERROR_MAX_STRING_SIZE, ret);
                printf("Error while reading frame: %s\n", errbuf);
                break;
            }
        }

        if (packet.stream_index == client->video_stream_index) {
            frame = av_frame_alloc();
            if (!frame) {
                printf("Error allocating frame\n");
                av_packet_unref(&packet);
                break;
            }

            ret = avcodec_send_packet(client->pCodecCtx, &packet);
            if (ret < 0) {
                av_frame_free(&frame);
                av_packet_unref(&packet);
                char errbuf[AV_ERROR_MAX_STRING_SIZE];
                av_make_error_string(errbuf, AV_ERROR_MAX_STRING_SIZE, ret);
                printf("Error sending packet to decoder: %s\n", errbuf);
                break;
            }

            while (ret >= 0) {
                ret = avcodec_receive_frame(client->pCodecCtx, frame);
                if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
                    av_frame_free(&frame);
                    break;
                } else if (ret < 0) {
                    av_frame_free(&frame);
                    char errbuf[AV_ERROR_MAX_STRING_SIZE];
                    av_make_error_string(errbuf, AV_ERROR_MAX_STRING_SIZE, ret);
                    printf("Error receiving frame from decoder: %s\n", errbuf);
                    break;
                }

                if (frame->pts != AV_NOPTS_VALUE) {
                    pts = av_rescale_q(frame->pts, client->pFormatCtx->streams[client->video_stream_index]->time_base, AV_TIME_BASE_Q);
                } else {
                    duration = av_frame_get_pkt_duration(frame);
                    pts = last_frame_pts + duration;
                }

                last_frame_pts = pts;

                buffer_size = av_image_get_buffer_size(client->pCodecCtx->pix_fmt, client->pCodecCtx->width, client->pCodecCtx->height, 1);
                buffer = (uint8_t*)av_malloc(buffer_size);
                av_image_fill_arrays(frame->data, frame->linesize, buffer, client->pCodecCtx->pix_fmt, client->pCodecCtx->width, client->pCodecCtx->height, 1);

                av_init_packet(&packet);
                packet.data = buffer;
                packet.size = buffer_size;
                packet.pts = pts;
                packet.dts = pts;
                packet.duration = duration;
                packet.stream_index = 0;

                gettimeofday(&tv, NULL);
                start_time = tv.tv_sec * 1000000 + tv.tv_usec;

                av_packet_rescale_ts(&packet, client->pFormatCtx->streams[client->video_stream_index]->time_base, client->pFormatCtx->streams[0]->time_base);

                ret = av_interleaved_write_frame(client->pFormatCtx, &packet);
                if (ret < 0) {
                    char errbuf[AV_ERROR_MAX_STRING_SIZE];
                    av_make_error_string(errbuf, AV_ERROR_MAX_STRING_SIZE, ret);
                    printf("Error writing frame: %s\n", errbuf);
                }

                gettimeofday(&tv, NULL);
                end_time = tv.tv_sec * 1000000 + tv.tv_usec;

                sleep_time = (duration * 1000000 - (end_time - start_time)) / 1000;
                if (sleep_time > 0) {
                    usleep(sleep_time);
                }

                av_packet_unref(&packet);
                av_free(buffer);
                av_frame_free(&frame);
            }
        } else {
            av_packet_unref(&packet);
        }
    }

    avformat_close_input(&client->pFormatCtx);
    avcodec_free_context(&client->pCodecCtx);
    av_frame_free(&client->pFrame);
    sws_freeContext(client->img_convert_ctx);
    close(client->socket);
    client->state = 0;

    return NULL;
}

int main(int argc, char *argv[]) {
    int ret;
    int server_socket;
    int client_socket;
    struct sockaddr_in server_address;
    struct sockaddr_in client_address;
    socklen_t client_address_len;
    char buf[1024];
    int n;
    int i;
    int optval;
    RTSPClient *client;

    av_register_all();
    avformat_network_init();

    server_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (server_socket < 0) {
        printf("Error creating socket: %s\n", strerror(errno));
        return 1;
    }

    optval = 1;
    setsockopt(server_socket, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));

    memset(&server_address, 0, sizeof(server_address));
    server_address.sin_family = AF_INET;
    server_address.sin_addr.s_addr = htonl(INADDR_ANY);
    server_address.sin_port = htons(RTSP_PORT);

    ret = bind(server_socket, (struct sockaddr*)&server_address, sizeof(server_address));
    if (ret < 0) {
        printf("Error binding socket: %s\n", strerror(errno));
        close(server_socket);
        return 1;
    }

    ret = listen(server_socket, 5);
    if (ret < 0) {
        printf("Error listening on socket: %s\n", strerror(errno));
        close(server_socket);
        return 1;
    }

    for (i = 0; i < MAX_CLIENTS; i++) {
        clients[i].state = 0;
    }

    while (1) {
        client_address_len = sizeof(client_address);
        client_socket = accept(server_socket, (struct sockaddr*)&client_address, &client_address_len);
        if (client_socket < 0) {
            printf("Error accepting connection: %s\n", strerror(errno));
            continue;
        }

        for (i = 0; i < MAX_CLIENTS; i++) {
            if (clients[i].state == 0) {
                client = &clients[i];
                break;
            }
        }

        if (i == MAX_CLIENTS) {
            printf("Too many clients\n");
            close(client_socket);
            continue;
        }

        client->state = 1;
        client->socket = client_socket;
        client->address = client_address;

        client->pFormatCtx = avformat_alloc_context();
        client->pCodecCtx = NULL;
        client->pCodec = NULL;
        client->pFrame = NULL;
        client->img_convert_ctx = NULL;
        client->video_stream_index = -1;

        ret = avformat_open_input(&client->pFormatCtx, "video.mp4", NULL, NULL);
        if (ret < 0) {
            char errbuf[AV_ERROR_MAX_STRING_SIZE];
            av_make_error_string(errbuf, AV_ERROR_MAX_STRING_SIZE, ret);
            printf("Error opening input file: %s\n", errbuf);
            close(client_socket);
            client->state = 0;
            continue;
        }

        ret = avformat_find_stream_info(client->pFormatCtx, NULL);
        if (ret < 0) {
            char errbuf[AV_ERROR_MAX_STRING_SIZE];
            av_make_error_string(errbuf, AV_ERROR_MAX_STRING_SIZE, ret);
            printf("Error finding stream info: %s\n", errbuf);
            avformat_close_input(&client->pFormatCtx);
            close(client_socket);
            client->state = 0;
            continue;
        }

        for (i = 0; i < client->pFormatCtx->nb_streams; i++) {
            if (client->pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
                client->video_stream_index = i;
                break;
            }
        }

        if (client->video_stream_index == -1) {
            printf("No video stream found\n");
            avformat_close_input(&client->pFormatCtx);
            close(client_socket);
            client->state = 0;
            continue;
        }

        client->pCodec = avcodec_find_decoder(client->pFormatCtx->streams[client->video_stream_index]->codecpar->codec_id);
        if (!client->pCodec) {
            printf("Codec not found\n");
            avformat_close_input(&client->pFormatCtx);
            close(client_socket);
            client->state = 0;
            continue;
        }

        client->pCodecCtx = avcodec_alloc_context3(client->pCodec);
        if (!client->pCodecCtx) {
            printf("Error allocating codec context\n");
            avformat_close_input(&client->pFormatCtx);
            close(client_socket);
            client->state = 0;
            continue;
        }

        ret = avcodec_parameters_to_context(client->pCodecCtx, client->pFormatCtx->streams[client->video_stream_index]->codecpar);
        if (ret < 0) {
            char errbuf[AV_ERROR_MAX_STRING_SIZE];
            av_make_error_string(errbuf, AV_ERROR_MAX_STRING_SIZE, ret);
            printf("Error setting codec parameters: %s\n", errbuf);
            avcodec_free_context(&client->pCodecCtx);
            avformat_close_input(&client->pFormatCtx);
            close(client_socket);
            client->state = 0;
            continue;
        }

        ret = avcodec_open2(client->pCodecCtx, client->pCodec, NULL);
        if (ret < 0) {
            char errbuf[AV_ERROR_MAX_STRING_SIZE];
            av_make_error_string(errbuf, AV_ERROR_MAX_STRING_SIZE, ret);
            printf("Error opening codec: %s\n", errbuf);
            avcodec_free_context(&client->pCodecCtx);
            avformat_close_input(&client->pFormatCtx);
            close(client_socket);
            client->state = 0;
            continue;
        }

        client->pFrame = av_frame_alloc();
        if (!client->pFrame) {
            printf("Error allocating frame\n");
            avcodec_free_context(&client->pCodecCtx);
            avformat_close_input(&client->pFormatCtx);
            close(client_socket);
            client->state = 0;
            continue;
        }

        client->img_convert_ctx = sws_getContext(client->pCodecCtx->width, client->pCodecCtx->height, client->pCodecCtx->pix_fmt, client->pCodecCtx->width, client->pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
        if (!client->img_convert_ctx) {
            printf("Error creating img_convert_ctx\n");
            av_frame_free(&client->pFrame);
            avcodec_free_context(&client->pCodecCtx);
            avformat_close_input(&client->pFormatCtx);
            close(client_socket);
            client->state = 0;
            continue;
        }

        ret = pthread_create(&client->thread_id, NULL, client_thread, client);
        if (ret != 0) {
            printf("Error creating thread\n");
            av_frame_free(&client->pFrame);
            sws_freeContext(client->img_convert_ctx);
            avcodec_free_context(&client->pCodecCtx);
            avformat_close_input(&client->pFormatCtx);
            close(client_socket);
            client->state = 0;
            continue;
        }
    }

    for (i = 0; i < MAX_CLIENTS; i++) {
        if (clients[i].state == 1) {
            clients[i].is_running = false;
            pthread_join(clients[i].thread_id, NULL);
            av_frame_free(&clients[i].pFrame);
            sws_freeContext(clients[i].img_convert_ctx);
            avcodec_free_context(&clients[i].pCodecCtx);
            avformat_close_input(&clients[i].pFormatCtx);
            close(clients[i].socket);
        }
    }

    avformat_network_deinit();
    av_free_all();

    return 0;
}

3. 启动 RTSP 服务器：你需要在终端上运行上面编写好的 C++ 程序，然后根据需要设置你的客户端连接地址和端口号，并开始发送数据。

以上就是使用 C++ 和 FFmpeg 创建 RTSP 服务器的基本步骤。如果你不想从头开始编写代码，也可以使用现成的 RTSP 服务器实现，如 Live555 或者 FFmpeg 提供的 RTSP 服务器。