Lookit experiment runner updates

The Lookit experiment runner is regularly updated in order to add new features and fix bugs. While you can find the details of all changes in the experiment runner Github repository, sometimes the changes don’t have much impact on researchers, or the descriptions on Github are written from a software development perspective. For this reason, we’ve added this page to highlight any changes that might be of particular interest to researchers, and to explain the changes from the standpoint of the impact on researchers.

Feb 21, 2024: Fix recording bug in Chrome [CRITICAL]

Commit SHA: b6567ade6674c245c69157361111e94250ab3b77

Github pull request: https://github.com/lookit/ember-lookit-frameplayer/pull/365

This change fixes a problem with the new recording system in Chrome, where initiating a recording with “video/webm” as the mime type (without specifying the codec) was sometimes producing recordings that could not be replayed by the participant or viewed by researchers in the web browser. This meant that participants were sometimes not able to replay their own recordings, and researchers were sometimes unable to view consent videos on the Consent Manager page. This update fixes the problem by checking the browser’s support for specific codecs and setting this accordingly when recording begins.


If you are already using the new RecordRTC system, please update your experiment runner to this version (or newer) immediately.

Jan 30, 2024: New Recording System

Commit SHA: 5f358868aade7689071565d881c9dd9050620d87

Github pull request: https://github.com/lookit/ember-lookit-frameplayer/pull/349

Key Information

  • We are switching how participant videos are handled by Lookit from a third-party service called ‘Pipe’ to a new system called ‘RecordRTC’ that is managed by the Lookit development team.
  • This change will affect all new studies by default. Existing studies will have the opportunity to update to the new system.
  • If you download participant videos, be aware that in the new system, the default file format for the videos is changing from .mp4 to .webm. We provide information on how to convert .webm files to .mp4s below, if needed.
  • Please let us know if you experience any problems using the new system. It is possible to switch back to the old Pipe system for a limited time if you experience issues.

Detailed Notes

The latest version of the Lookit experiment runner switched from using a third-party service (called ‘Pipe’) for participant video recordings to our new ‘in-house’ system called ‘RecordRTC’. Our reasons for removing Lookit’s dependence on the external Pipe service are:

  • Simplifying participant video handling and reducing the likelihood of video rendering issues, as videos will now be processed on Lookit’s own servers rather than via a third-party service.
  • Lowering the website’s running costs. Pipe usage accounts for a large proportion of CHS/Lookit’s expenses, and these costs grow with increasing use of the website.
  • Preventing problems caused by unexpected updates to Pipe that we have no control over.
  • Removing third-party access to private and sensitive research data. Although this service was secure, this reduces the theoretical chances of data leaks and improper data use/access by keeping this data only on Lookit servers.

All studies will eventually need to switch!

Moving forward, all new studies will use RecordRTC but existing studies will continue to use Pipe, unless the researcher decides to update their experiment runner version.

The old Pipe system will be discontinued in the future (exact date TBD; we will announce ahead of time). For the time being, we are running the new and old systems in parallel. This is to allow ongoing studies to continue to use the Pipe system for the remainder of their data collection, and to allow a fallback option in case of unforeseen problems with the new system. For any studies you will be using or copying in the future, we strongly recommend that you update your experiment runner to test this new system before the support for Pipe ends!

Checking which recording system your study is using

The easiest way to check is to go to the Study Details page for your study, find the “About this version” section, and look for the commit SHA and date (see screenshot below).

  • Before January 30th 2024 (2024-01-30): old Pipe system
  • On or after January 30th 2024 (2024-01-30): new RecordRTC system
Study Details page with information about the study's experiment runner version.

You can also click the “Check for updates” button (see screenshot above) to see what changes, if any, have been made to the experiment runner since the version that your experiment is currently using.

By default, newly-created experiments will use our new recording system. However, with any new or existing study, you can change the experiment runner version at any time (see the section “Switching an existing experiment to the new system” and the page “Updating the experiment runner”).

The first commit SHA that uses the new recording version is: 5f358868aade7689071565d881c9dd9050620d87. All future updates (commits on the master branch) to our experiment runner will also use the new recording system. You can find an up-to-date list of all versions and associated commit SHAs here.

Switching an existing experiment to the new system

If you have an existing study that uses the old Pipe system and would like to switch to using the new recording system, the easiest way to switch is to click the ‘Check for updates’ button on your Study Details page, and then copy/paste the most recent commit SHA into the ‘Experiment runner version’ box. For more details on how to do this, see the Updating the experiment runner page.

If you change your study’s experiment runner verison, remember:

  • You will need to rebuild your experiment runner. You will see a ‘Build experiment runner’ button on your study’s main page. Click this button to build your study with the new version.
  • If your study has already been approved, it will be automatically rejected. When you re-submit it for approval, you will be asked to list all changes made since your study was last approved. If you have only updated the experiment runner, please state that clearly so that we can get your study approved more quickly!

Impact on data

We have worked to minimize the impact that this new recording system has on researchers and data, but it does introduce a few changes:

  • Video file format is webm rather than mp4 (see section ‘Converting webm to mp4’)
  • Video file size may be larger
  • Pipe Id is no longer included in the response data. This category was previously included because the Pipe system renamed video files during processing and we needed to know both the original name and the Pipe name for troubleshooting issues. Now, video file names will be the same throughout all processes.

Converting webm to mp4

Webm is the ‘native’ format that the web browser uses when creating webcam recordings. By providing you with these raw data files, we can ensure that you’re getting the most detailed video data possible. Webm files can be opened and viewed in many video playback programs, including web browsers and VLC.

However, we are aware that the change in file formats might cause problems for some researchers who require mp4 format for their data processing and analysis. And because the webm files are larger than the files produced by the old system, you may decide to compress your video files into mp4 format so that they take up less disk space.

Handbrake (GUI)

For a free GUI-based file conversion tool, we suggest using Handbrake. After downloading and installing Handbrake:

  1. Open your .webm video file in Handbrake (click “Open Source”, or drag and drop the file).
  2. In the “Format” drop-down, select “MP4”.
  3. Set your file output location (Shown at the bottom next to “Save As” - change the location by clicking “Browse…”).
  4. Click the “Start” button at the top.

To batch convert several files at once, you can open all the .webm files you want to convert by clicking ‘Open Source’ and selecting multiple files (by holding down CTRL/CMD or Shift). Then, just follow the steps above (select the file format and output location, and then click “Start”).

For more information, see the Handbrake quick start guide.

ffmpeg (command line)

For converting files on the command line, we recommend using the ffmpeg software. The examples below show the most basic webm -> mp4 file conversion, but the ffmpeg command offers a number of other options that you might find useful, such as adjusting the bitrate/resolution/quality.

On a Mac, open a terminal window and install ffmpeg like this:

brew install ffmpeg

To convert a single file:

ffmpeg -i input-filename.webm output-filename.mp4

To batch convert a directory of files:

for i in *.webm; do ffmpeg -i "$i" "${i%.*}.mp4"; done

The above code will save the mp4 files to the same directory. You can save them to a different directory by editing to the ‘output’ file path, e.g. "mp4_files/${i%.*}.mp4" will put the mp4 files into a subdirectory called ‘mp4_files’.

On Windows, you will need to download the ffmpeg exe file to install it. See the ffmpeg website for downloads and here for more instructions.

To convert a single file:

ffmpeg -i input-filename.webm output-filename.mp4

To batch convert a directory of files:

for %f in (*.*) do ffmpeg -i "%f" "%~nf.mp4"

The above code will save the mp4 files to the same directory. You can save them to a different directory by editing to the ‘output’ file path, e.g. "mp4_files/%~nf.mp4" will put the mp4 files into a subdirectory called ‘mp4_files’.

What if I experience problems with the new system?

If you experience any issues that you think might be related to the new recording system, please let us know immediately by posting in the Slack tech_support channel! Give us a short description of the problem and a link to your study.

If you’re in the middle of data collection or need to start quickly, remember that you always have the option to switch your study back to the old Pipe recording system. The commit SHA for the last version of the experiment runner that uses the Pipe system is: ba09c18f6f04d3fe6017722a0388e100378faef3. On your ‘Study Details’ page, you can paste this commit SHA into the ‘Experiment runner version’ textbox, save the changes, and rebuild your experiment runner.

Keep in mind that we are transitioning away from the old Pipe system, so the option to revert back will only be available for a limited time. You might decide to continue using the Pipe system if you have already begun collecting data and will finish soon, or if you have experienced problems with the new system that are interfering with your data collection. Otherwise, we strongly suggest using the new system so that you have time to test it with your study before we discontinue support for Pipe.

Oct 16, 2023: Add ‘iframe’ frame

Commit SHA: ea4169716acb6330f14ba80d79854269e7c859e1

Github pull request: https://github.com/lookit/ember-lookit-frameplayer/pull/340

This update added a new ‘iframe’ frame, which allows the researcher to embed an external webpage (e.g. Qualtrics) into an interal Lookit experiment. There are some important limitations to this approach, but it can be useful for researchers who want to record video while participants are completing the external survey/task. See the exp-lookit-iframe documentation here.

Oct 10, 2023: Fix webcam display

Commit SHA: bc5ffc1ab7b6c1d167d8434862d6bf4cc3bb4550

Github pull request: https://github.com/lookit/ember-lookit-frameplayer/pull/334

This change fixed the problem with the Pipe webcam display in the video-consent frame and other frames that display the webcam back to the participant. The problem was that the webcam video display box can cover up other elements on the page, including text and recording start/stop buttons.

This update fixes the webcam display problem on the following frames:

  • instructions
  • observation
  • video-assent
  • video-consent
  • webcam-display
  • video-config
  • video-config-quality