Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

Supported by

How to time visual stimuli correctly

Hi there,

I am running some timing tests with Expyriment. I am using a LabJack to fire a TTL pulse and then measuring the time it takes for the stimuli to appear on screen (using a Black Box Tool Kit). Here is the minimal code - note, stimuli[0] is a blank screen, and stimuli[1] is a rectangle stimulus:

# Preload blank screen
trial.stimuli[0].preload()
expLabJack.writeRegister(6004, 0)
trial.stimuli[0].present(clear=False, update=False) 
# Preload stim
trial.stimuli[1].preload()
exp.clock.wait(300)

# Fire TTL pulse
expLabJack.writeRegister(6004, 1)
# present stim
trial.stimuli[1].present(clear=False, update=False)
exp.clock.wait(200)
expLabJack.writeRegister(6004, 0)

The problem I am having: Using this method, it takes approximately 28ms for the visual stimuli to be detected onscreen (visual stimuli onset - TTL pulse onset), so onset times of the stimuli are overshooting by at least a frame. Is there a better way of controlling the presentation of stimuli?

Comments

  • Hi,

    in your example, nothing should be shown on the screen, since you explicitely set update=False.
    What are the results of the visual presentation test in the test suite for you? Maybe we can go from there.

  • Thanks for the response. Apologies, that is a typo. The stimuli itself does not have an arg passed to the update parameter. Will get the test suite results now.

  • Here is the output of the test suite (had to cut some of the list entries due to character limit). If you would like it in a different format please let me know:

    hardware_audio_card:
    hardware_cpu_architecture: AMD64
    hardware_cpu_details: Intel(R) Xeon(R) CPU E5-1620 v2 @ 3.70GHz
    hardware_cpu_type: Intel64 Family 6 Model 62 Stepping 4, GenuineIntel
    hardware_disk_space_free: 44015 MB
    hardware_disk_space_total: 244196 MB
    hardware_internet_connection: Yes
    hardware_memory_free: 25342 MB
    hardware_memory_total: 32683 MB
    hardware_ports_parallel: []
    hardware_ports_parallel_driver: None
    hardware_ports_serial: []
    hardware_video_card: RDPDD Chained DD
    os_architecture: 64bit
    os_details: SP1
    os_name: Windows
    os_platform: Windows
    os_release: 7
    os_version: 6.1.7601
    python_expyriment_build_date: Thu Mar 9 13:48:59 2017 +0100
    python_expyriment_revision: c4963ac
    python_expyriment_version: 0.9.0
    python_mediadecoder_version:
    python_numpy_version:
    python_pil_version:
    python_pygame_version: 1.9.4
    python_pyopengl_version: 3.1.0
    python_pyparallel_version:
    python_pyserial_version:
    python_sounddevice_version:
    python_version: 3.6.5
    settings_folder: None
    testsuite_visual_flipping_user: 1
    testsuite_visual_opengl: 2
    testsuite_visual_opengl_extensions: ['GL_AMD_multi_draw_indirect', 'GL_ARB_arrays_of_arrays', 'GL_ARB_base_instance', 'GL_ARB_blend_func_extended', 'GL_ARB_buffer_storage', 'GL_ARB_clear_buffer_object', 'GL_ARB_clear_texture', 'GL_ARB_color_buffer_float', 'GL_ARB_compatibility', 'GL_ARB_compressed_texture_pixel_storage', 'GL_ARB_conservative_depth', 'GL_ARB_compute_shader', 'GL_ARB_compute_variable_group_size', 'GL_ARB_copy_buffer', 'GL_ARB_copy_image', 'GL_ARB_debug_output', 'GL_ARB_depth_buffer_float', 'GL_ARB_depth_clamp', 'GL_ARB_depth_texture', 'GL_ARB_draw_buffers', 'GL_ARB_draw_buffers_blend', 'GL_ARB_draw_indirect', 'GL_ARB_draw_elements_base_vertex', 'GL_ARB_draw_instanced', 'GL_ARB_enhanced_layouts', ...[DELETED ENTRIES DUE TO CHAR LIMIT]]
    testsuite_visual_opengl_renderer: b'NVS 310/PCIe/SSE2'
    testsuite_visual_opengl_vendor: b'NVIDIA Corporation'
    testsuite_visual_opengl_version: b'4.4.0'
    testsuite_visual_pygame_driver: windib
    testsuite_visual_pygame_screensize: (1920, 1080)
    testsuite_visual_sync_refresh_rate: 60.0 Hz
    testsuite_visual_timing_actual: [16.57459940179251, 33.29449532611761, 50.0559045758564, 16.66592866240535, 66.72127972706221, 33.18213266902603, 16.6681426926516, 33.33130379905924, 16.694434452801943, 33.220601675566286, 50.06171643617563, 16.662054069456644, 16.67976642784197, 33.33462486625649, 16.68281073216349, 49.99916972883511, 49.88210223382339, 66.64960009220522, 16.666482159052975, 16.66482162545435, 49.99833946931176, 66.6969252488343, ...]
    testsuite_visual_timing_delay_histogram: {16: 5, 2: 9, 13: 13, 6: 8, 9: 12, 4: 9, 11: 12, 14: 11, 0: 12, 7: 12, 3: 9, 5: 9, 8: 12, 12: 12, 1: 10, 17: 1, 10: 13, 15: 11}
    testsuite_visual_timing_delayed: 2.22 %
    testsuite_visual_timing_inaccuracy: 0 ms
    testsuite_visual_timing_todo: [0, 31, 37, 10, 57, 29, 5, 19, 17, 26, 47, 11, 8, 30, 5, 45, 36, 54, 9, 15, 41, 59, 25, 34, 33, 9, 28, 39, 44, 59, 48, 30, 11, 44, 54, 27, 2, 9, 43, 57, 18, 27, 8, 28, 26, 18, 7, 22, 20, 42, 31, 0, 34, 42, 39, 40, 4, 40, 1, 12, 52, 45, 22, 33, 52, 12, 50, 38, 21, 7, 16, 53, 5, 0, 46, 29, 7, 6, 40, 25, 23, 41, 19, 55, 56, 45, 17, 54, 56, 33, 49, 14, 2, 20, 12, 1, 37, 39, 4, 10, 6, 46, 35, 10, 46, 31, 13, 24, 2, 16, 53, 4, 11, 3, 20, 19, 48, 32, 49, 22, 27, 58, 32, 8, 59, 55, 17, 58, 14, 51, 24, 57, 3, 16, 43, 3, 34, 15, 6, 51, 23, 24, 36, 25, 37, 35, 1, 50, 56, 15, 13, 29, 52, 21, 53, 42, 48, 41, 51, 43, 30, 28, 47, 58, 50, 35, 55, 38, 36, 18, 47, 13, 23, 38, 26, 44, 49, 21, 14, 32]

  • The code without typo:

    # Preload blank screen
    trial.stimuli[0].preload()
    expLabJack.writeRegister(6004, 0)
    trial.stimuli[0].present(clear=False) 
    # Preload stim
    trial.stimuli[1].preload()
    exp.clock.wait(300)
    
    # Fire TTL pulse
    expLabJack.writeRegister(6004, 1)
    # present stim
    trial.stimuli[1].present(clear=False)
    exp.clock.wait(200)
    expLabJack.writeRegister(6004, 0)
    
  • Ok, turns out the TTL should be fired after the call to present the stimuli. With that, I can achieve screen latencies of 11ms. Thanks for reading.

Sign In or Register to comment.

agen judi bola , sportbook, casino, togel, number game, singapore, tangkas, basket, slot, poker, dominoqq, agen bola. Semua permainan bisa dimainkan hanya dengan 1 ID. minimal deposit 50.000 ,- bonus cashback hingga 10% , diskon togel hingga 66% bisa bermain di android dan IOS kapanpun dan dimana pun. poker , bandarq , aduq, domino qq , dominobet. Semua permainan bisa dimainkan hanya dengan 1 ID. minimal deposit 10.000 ,- bonus turnover 0.5% dan bonus referral 20%. Bonus - bonus yang dihadirkan bisa terbilang cukup tinggi dan memuaskan, anda hanya perlu memasang pada situs yang memberikan bursa pasaran terbaik yaitu http://45.77.173.118/ Bola168. Situs penyedia segala jenis permainan poker online kini semakin banyak ditemukan di Internet, salah satunya TahunQQ merupakan situs Agen Judi Domino66 Dan BandarQ Terpercaya yang mampu memberikan banyak provit bagi bettornya. Permainan Yang Di Sediakan Dewi365 Juga sangat banyak Dan menarik dan Peluang untuk memenangkan Taruhan Judi online ini juga sangat mudah . Mainkan Segera Taruhan Sportbook anda bersama Agen Judi Bola Bersama Dewi365 Kemenangan Anda Berapa pun akan Terbayarkan. Tersedia 9 macam permainan seru yang bisa kamu mainkan hanya di dalam 1 ID saja. Permainan seru yang tersedia seperti Poker, Domino QQ Dan juga BandarQ Online. Semuanya tersedia lengkap hanya di ABGQQ. Situs ABGQQ sangat mudah dimenangkan, kamu juga akan mendapatkan mega bonus dan setiap pemain berhak mendapatkan cashback mingguan. ABGQQ juga telah diakui sebagai Bandar Domino Online yang menjamin sistem FAIR PLAY disetiap permainan yang bisa dimainkan dengan deposit minimal hanya Rp.25.000. DEWI365 adalah Bandar Judi Bola Terpercaya & resmi dan terpercaya di indonesia. Situs judi bola ini menyediakan fasilitas bagi anda untuk dapat bermain memainkan permainan judi bola. Didalam situs ini memiliki berbagai permainan taruhan bola terlengkap seperti Sbobet, yang membuat DEWI365 menjadi situs judi bola terbaik dan terpercaya di Indonesia. Tentunya sebagai situs yang bertugas sebagai Bandar Poker Online pastinya akan berusaha untuk menjaga semua informasi dan keamanan yang terdapat di POKERQQ13. Kotakqq adalah situs Judi Poker Online Terpercayayang menyediakan 9 jenis permainan sakong online, dominoqq, domino99, bandarq, bandar ceme, aduq, poker online, bandar poker, balak66, perang baccarat, dan capsa susun. Dengan minimal deposit withdraw 15.000 Anda sudah bisa memainkan semua permaina pkv games di situs kami. Jackpot besar,Win rate tinggi, Fair play, PKV Games