写一段c++ 使用ffmpeg库，解析rtsp流并转码到H264

以下是一段使用ffmpeg库解析rtsp流并将其转码为H264的C代码：

#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>

int main(int argc, char *argv[]) {
    AVFormatContext *pFormatCtx = NULL;
    int videoStream, i;
    AVCodecContext *pCodecCtx = NULL;
    AVCodec *pCodec = NULL;
    AVFrame *pFrame = NULL;
    AVPacket packet;
    int frameFinished;
    AVFrame *pFrameRGB = NULL;
    uint8_t *buffer = NULL;
    struct SwsContext *sws_ctx = NULL;
  
    av_register_all();

    // 打开rtsp流
    if (avformat_open_input(&pFormatCtx, "rtsp://stream_url", NULL, NULL) != 0) {
        fprintf(stderr, "Couldn't open input stream.\n");
        return -1;
    }

    // 查找流信息
    if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
        fprintf(stderr, "Couldn't find stream information.\n");
        return -1;
    }

    // 找到视频流
    videoStream = -1;
    for (i = 0; i < pFormatCtx->nb_streams; i++) {
        if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoStream = i;
            break;
        }
    }
    if (videoStream == -1) {
        fprintf(stderr, "Couldn't find video stream.\n");
        return -1;
    }

    // 获取视频流的编解码器上下文
    pCodecCtx = pFormatCtx->streams[videoStream]->codec;

    // 查找解码器
    pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    if (pCodec == NULL) {
        fprintf(stderr, "Unsupported codec!\n");
        return -1;
    }

    // 打开解码器
    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        fprintf(stderr, "Could not open codec.\n");
        return -1;
    }

    // 分配一个AVFrame并初始化
    pFrame = av_frame_alloc();
    pFrameRGB = av_frame_alloc();
    if