playback keep reading the same frames while writing frames to disk by stbi_write_png

[hflsdupont]

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Required Info
Camera Model	D435
Firmware Version	5.9.14
Operating System & Version	Win10
Platform	PC
SDK Version	2.14.1

Issue Description

Hi, I'm currently using playback to read from two rosbag files and synchronize those frames. As far as I don't write those frames to disk by stb, pipe.wait_for_frames() return each frames in .bag file correctly. However, when I try to call stbi_write_png, the next call of playback.resume() and pipe.wait_for_frames() return exactly the same frameset as the previous one.

  auto device = pipe.get_active_profile().get_device();
  rs2::playback playback = device.as<rs2::playback>();

  playback.resume();
  frameset = pipe.wait_for_frames(); 
  playback.pause();

void saveImages(video_frame & f, std::stringstream & filename, std::string & dir, std::string & subdir)
{
  std::stringstream path; 
  path << dir << "\\" << subdir << "\\" << filename.str(); 
  
  stbi_write_png(path.str().c_str(), f.get_width(), f.get_height(),
            f.get_bytes_per_pixel(), f.get_data(), f.get_stride_in_bytes());
  
  std::cout << "Saved " << path.str() << std::endl;
}

Thanks for the help

[dorodnic]

Hi @hflsdupont
We are looking into this issue. The short story is that pause and resume have some unintended consequences on synchronization. If you avoid pause and resume I believe you will get the frames in correct sequence, but processing is likely to cause frame drops. One idea (I still need to test) is decreasing playback speed.

[hflsdupont]

Hi @dorodnic
Thank you for the quick reply. I noticed playback.set_real_time() has similar functions as calling pause and resume, but it doesn't work for me as well. I'll try decreasing playback speed.

[dorodnic]

Hi @hflsdupont
Sorry for long delay. We believe this should be now resolved (since 2.16.1 release).
Do you need additional support on this issue?