使用C++和ffmpeg从mp2流中提取KLV数据

#include <iostream>
#include <string>
extern "C" {
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
}

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

    // 打开mp2文件或流
    AVFormatContext* formatContext = nullptr;
    std::string inputFilePath = "input.mp2";
    if (avformat_open_input(&formatContext, inputFilePath.c_str(), nullptr, nullptr) != 0) {
        std::cerr << "Failed to open input file" << std::endl;
        return -1;
    }

    // 查找包含KLV数据的音频流
    int audioStreamIndex = -1;
    for (unsigned int i = 0; i < formatContext->nb_streams; i++) {
        if (formatContext->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
            audioStreamIndex = i;
            break;
        }
    }

    if (audioStreamIndex == -1) {
        std::cerr << "No audio stream found" << std::endl;
        avformat_close_input(&formatContext);
        return -1;
    }

    // 创建解码器上下文
    AVCodecContext* codecContext = avcodec_alloc_context3(nullptr);
    if (!codecContext) {
        std::cerr << "Failed to allocate codec context" << std::endl;
        avformat_close_input(&formatContext);
        return -1;
    }

    // 设置解码器参数
    if (avcodec_parameters_to_context(codecContext, formatContext->streams[audioStreamIndex]->codecpar) < 0) {
        std::cerr << "Failed to copy codec parameters to context" << std::endl;
        avcodec_free_context(&codecContext);
        avformat_close_input(&formatContext);
        return -1;
    }

    // 打开解码器
    AVCodec* codec = avcodec_find_decoder(codecContext->codec_id);
    if (!codec) {
        std::cerr << "Failed to find decoder" << std::endl;
        avcodec_free_context(&codecContext);
        avformat_close_input(&formatContext);
        return -1;
    }

    if (avcodec_open2(codecContext, codec, nullptr) < 0) {
        std::cerr << "Failed to open codec" << std::endl;
        avcodec_free_context(&codecContext);
        avformat_close_input(&formatContext);
        return -1;
    }

    // 读取音频帧并提取KLV数据
    AVPacket packet;
    av_init_packet(&packet);
    while (av_read_frame(formatContext, &packet) >= 0) {
        if (packet.stream_index == audioStreamIndex) {
            // 解码音频帧
            AVFrame* frame = av_frame_alloc();
            int ret = avcodec_send_packet(codecContext, &packet);
            if (ret < 0) {
                std::cerr << "Error sending a packet for decoding" << std::endl;
                av_frame_free(&frame);
                break;
            }

            ret = avcodec_receive_frame(codecContext, frame);
            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
                av_frame_free(&frame);
                continue;
            } else if (ret < 0) {
                std::cerr << "Error during decoding" << std::endl;
                av_frame_free(&frame);
                break;
            }

            // 提取KLV数据并进行处理
            // ...

            av_frame_free(&frame);
        }

        av_packet_unref(&packet);
    }

    // 清理资源
    avcodec_free_context(&codecContext);
    avformat_close_input(&formatContext);

    return 0;
}