HarmonyOS 鸿蒙Next 怎么MP4文件解封装读取h264裸流

HarmonyOS 鸿蒙Next 怎么MP4文件解封装读取h264裸流 如题，我想从MP4文件中读取h264的裸流，然后按一帧一帧的打包成RTP包发送出去，我参考样例：https://gitee.com/harmonyos_samples/AVCodecVideo 代码，但是在以下是output线程的代码：

void ReadMp4::VideoDecOutputThread() {
    while (true) {
        thread_local auto lastPushTime = std::chrono::system_clock::now();
        CHECK_AND_BREAK_LOG(isStarted_, "Decoder output thread out");
        std::unique_lock<std::mutex> lock(videoDecContext_->outputMutex);
        bool condRet = videoDecContext_->outputCond.wait_for(
            lock, 5s, [this]() { return !isStarted_ || !videoDecContext_->outputBufferInfoQueue.empty(); });
        CHECK_AND_BREAK_LOG(isStarted_, "Decoder output thread out");
        CHECK_AND_CONTINUE_LOG(!videoDecContext_->outputBufferInfoQueue.empty(),
                               "Buffer queue is empty, continue, cond ret: %{public}d", condRet);

        CodecBufferInfo bufferInfo = videoDecContext_->outputBufferInfoQueue.front();
        videoDecContext_->outputBufferInfoQueue.pop();
        CHECK_AND_BREAK_LOG(!(bufferInfo.attr.flags & AVCODEC_BUFFER_FLAGS_EOS), "Catch EOS, thread out");
        videoDecContext_->outputFrameCount++;
        AVCODEC_SAMPLE_LOGW("Out buffer count: %{public}u, size: %{public}d, flag: %{public}u, pts: %{public}" PRId64,
                            videoDecContext_->outputFrameCount, bufferInfo.attr.size, bufferInfo.attr.flags,
                            bufferInfo.attr.pts);
        lock.unlock();
        
        napi_SendVideoOneFrame(
                reinterpret_cast<char*>(OH_AVBuffer_GetAddr(reinterpret_cast<OH_AVBuffer*>(bufferInfo.buffer)),
                bufferInfo.attr.size, "Playback", 0, ip, port);

        int32_t ret = videoDecoder_->FreeOutputBuffer(bufferInfo.bufferIndex, false);
        CHECK_AND_BREAK_LOG(ret == AVCODEC_SAMPLE_ERR_OK_, "Decoder output thread out");

        std::this_thread::sleep_until(lastPushTime + std::chrono::microseconds(sampleInfo_.frameInterval));
        lastPushTime = std::chrono::system_clock::now();
    }
    StartRelease();
}

但是这里bufferInfo.buffer返回的是固定大小的数据，不是SPS，PPS，I帧，P帧这样的一帧一帧的数据，请问哪里出错了吗？