写一个C++使用ffmpeg实现rtsp推流的代码

以下是使用FFmpeg实现RTSP推流的示例C代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <libavformat/avformat.h>
#include <libavutil/opt.h>

int main(int argc, char **argv)
{
    AVFormatContext *fmt_ctx = NULL;
    AVOutputFormat *out_fmt = NULL;
    AVStream *video_st = NULL;
    AVCodecContext *codec_ctx = NULL;
    AVCodec *codec = NULL;
    AVDictionary *options = NULL;
    int ret;

    const char *rtsp_url = "rtsp://your_rtsp_server_url";
    const char *out_filename = "rtsp_stream_output";

    // Register all available codecs and formats
    av_register_all();
    avformat_network_init();

    // Allocate output format context
    avformat_alloc_output_context2(&fmt_ctx, NULL, "rtsp", out_filename);
    if (!fmt_ctx) {
        fprintf(stderr, "Could not create output format context\n");
        return -1;
    }

    // Find video encoder codec
    codec = avcodec_find_encoder_by_name("h264");
    if (!codec) {
        fprintf(stderr, "Could not find video encoder codec\n");
        return -1;
    }

    // Allocate codec context and set options
    codec_ctx = avcodec_alloc_context3(codec);
    if (!codec_ctx) {
        fprintf(stderr, "Could not allocate codec context\n");
        return -1;
    }
    codec_ctx->bit_rate = 400000;
    codec_ctx->width = 640;
    codec_ctx->height = 480;
    codec_ctx->time_base = (AVRational){1, 25};
    codec_ctx->gop_size = 10;
    codec_ctx->pix_fmt = AV_PIX_FMT_YUV420P;
    av_opt_set(codec_ctx->priv_data, "preset", "ultrafast", 0);
    av_opt_set(codec_ctx->priv_data, "tune", "zerolatency", 0);

    // Open codec
    if ((ret = avcodec_open2(codec_ctx, codec, &options)) < 0) {
        fprintf(stderr, "Could not open codec: %s\n", av_err2str(ret));
        return -1;
    }

    // Add video stream to output format context
    video_st = avformat_new_stream(fmt_ctx, codec);
    if (!video_st) {
        fprintf(stderr, "Could not create new video stream\n");
        return -1;
    }
    avcodec_parameters_from_context(video_st->codecpar, codec_ctx);

    // Open output file or URL
    if ((ret = avio_open(&fmt_ctx->pb, rtsp_url, AVIO_FLAG_WRITE)) < 0) {
        fprintf(stderr, "Could not open output file or URL: %s\n", av_err2str(ret));
        return -1;
    }

    // Write header to output format context
    if ((ret = avformat_write_header(fmt_ctx, &options)) < 0) {
        fprintf(stderr, "Could not write header to output format context: %s\n", av_err2str(ret));
        return -1;
    }

    // Main loop to write video frames
    for (int i = 0; i < 1000; i++) {
        AVFrame *frame = av_frame_alloc();
        if (!frame) {
            fprintf(stderr, "Could not allocate video frame\n");
            return -1;
        }

        // Fill video frame with data
        // ...

        // Set frame PTS and duration
        frame->