log_capture feature has some problem, my guess.

[wuyong-ndrone]

Environment

• WSL debian bookwarm
• MAVSDK 2.12.12

Issues

I want to use the "log_capture" feature, and found some problems. My log is created between arm and disarm.

first log is good but after, not good

After the my program is started, the first log file is good. But after the second log file shows, (PlotJuggler)

And in HEX editor shows like this,

uLog file's header is gone. Again, first ulog file is ok.

So, I tried different way like this.

    if (_system)
    {
        if (enable) // start the log capture
        {
            _log_streaming       = std::make_shared<mavsdk::LogStreaming>(_system);
            _h_log_streaming_raw = _log_streaming->subscribe_log_streaming_raw(
                std::bind(&AutoPilot_Impl::onLogStreamingRaw, this, std::placeholders::_1));
            _log_streaming->start_log_streaming();
        }
        else // stop
        {
            _log_streaming->stop_log_streaming();
            _log_streaming->unsubscribe_log_streaming_raw(_h_log_streaming_raw);
            _log_streaming.reset();
        }
    }

In this case, second log file was good. ulog header is placed on start of file. But try to start the third log file, program is stuck like this.

Am I did something wrong?

[wuyong-ndrone]

Hi,
I found some problems in second log file.

After the second log file, some garbage is added in top of new file's header.

[julianoes]

I'm using log streaming with this version and it works for me, so my hunch is that you write invalid data somewhere. Can you share more of the code?

[wuyong-ndrone]

When mavlink is connected

    _h_log_streaming_raw = _log_streaming->subscribe_log_streaming_raw(
        std::bind(&AutoPilot_Impl::onLogStreamingRaw, this, std::placeholders::_1));

And, callback is

void AutoPilot_Impl::onLogStreamingRaw(mavsdk::LogStreaming::LogStreamingRaw log_raw)
{
    if (sigLogStreamingUpdated.num_slots() > 0)
    {
        auto log = mavsdk::base64_decode(log_raw.data);
        sigLogStreamingUpdated(log);
        // sigLogStreamingUpdated(log_raw.data);
    }
}

Log streaming start/stop

void AutoPilot_Impl::SetLogCapture(bool enable)
{
    if (_log_streaming)
    {
        if (enable)
            _log_streaming->start_log_streaming();
        else
            _log_streaming->stop_log_streaming();
    }
}

Before the log capture module is started,

    // register callback
    _config.autopilot_->SigLogStreamingUpdatedHandle().connect(
        boost::bind(&LogCapture_Impl::slotAutoPilotLogStreamingUpdated, this, boost::placeholders::_1));

Callback handler and circular buffer

// in header file
    boost::circular_buffer<std::vector<uint8_t>> _ring_buffer { 10 };

// and callback handler
void LogCapture_Impl::slotAutoPilotArmedUpdated(bool armed)
{
    _start_logging = armed;
}

void LogCapture_Impl::slotAutoPilotLogStreamingUpdated(std::vector<uint8_t>& log)
{
    std::lock_guard<std::mutex> locker(_ring_buffer_lock);
    _ring_buffer.push_back(log);
}

Here is log to file

void LogCapture_Impl::run()
{
    bool          logging { false };
    std::ofstream log_file;
    std::vector<uint8_t> log_row;

    // for stabilization delay
    std::this_thread::sleep_for(std::chrono::milliseconds(500));

    try
    {
        if (not std::filesystem::is_directory(_config.file_path_))
            std::filesystem::create_directories(_config.file_path_);
    }
    catch (std::exception& e)
    {
#ifndef NDEBUG
        std::cerr << e.what() << std::endl;
#endif
        _config.file_path_ = DEFAULT_LOGDIR;
        std::filesystem::create_directories(std::filesystem::path(_config.file_path_));
    }

    while (not _run_thread->interruption_requested())
    {
        if (logging != _start_logging)
        {
            logging = _start_logging;

            if (logging)
            {
                std::string file_path { _config.file_path_ + "/" + createFileName() };
                log_file.open(file_path, std::ios::binary);
                _config.autopilot_->SetLogCapture(true);
            }
            else
            {
                if (log_file.is_open())
                {
                    _config.autopilot_->SetLogCapture(false);
                    log_file.close();
                }
                _ring_buffer.clear();
            }
        }

        if (log_file.is_open() and (not _ring_buffer.empty()))
        {
            {
                std::lock_guard<std::mutex> locker(_ring_buffer_lock);
                log_row = _ring_buffer.front();
                _ring_buffer.pop_front();
            }

            log_file.write(reinterpret_cast<char*>(log_row.data()), log_row.size());
        }
        else
        {
            std::this_thread::sleep_for(std::chrono::milliseconds(2));
        }
    }
}

[julianoes]

Thanks. Looks correct from what I can see. The version I used/tested recently was the one on v2.12. So maybe I broke something when going to the base64 implementation. I will have to test this one when I upgrade to future v3.

[wuyong-ndrone]

I think the log is no need the base64 encoding. I think it just increase data size. If need the base64 encoding, it should process the user. Just my opinion.
Thank you for your fast reply.

[julianoes]

The problem is that we need to do base64 encoding for language wrappers like Python, because we can't send binary data there using the string type.