Skip to content

Closed Captions Correction manual


This manual is intended for people using Clevercast to edit closed captions which are the result from speech-to-text before they are shown in the video player or auto-translated into other languages. The interface for this is called a Corrector Room.

The room can be used to watch the incoming video stream and listen to the floor audio. In live streams with simultaneous audio translation, correctors can also use interpreter relay. The text chat on the bottom of the page allows for communication with event managers and other users.

The person using the room should receive a secure link from the event manager.

Important: make sure to read the requirements and best practices before you start using the correction room.

The Correction Room interface

This is the interface used for the editing of closed captions, which were generated through speech-to-text. If you are an editor, you will receive a secure link to your language’s Correction Room from the event’s manager. By using this link in Firefox, you automatically get access to the room. The user interface looks like this:

The ‘Correction Room’ interface for closed caption editing

The interface consists of the following elements:

  1. Connect/Disconnect button: before a user can start working, she has to connect to the correction room (in order to receive the incoming stream and send outgoing text).
  2. Player: plays the video and floor audio as soon as it is being broadcasted.
  3. Connection status: displays the status of the incoming captions and the outgoing text.
  4. Event status: the live event status. When the room is available it is set to Preview (testing in advance, viewers can not see and hear the live stream), Started (live) or Paused (viewers can not see and hear the live stream). If set to Inactive or Ended, the room is not available.
  5. Captions: a separate box is shown for each closed caption from the speech-to-text conversion. By editing the text in these boxes, you can correct the closed captions before they are shown in the video player.
  6. Messages window: allows a user to communicate with other transcribers for the same language and with their event managers. It also contains system messages (e.g. when someone joins or leaves the room).
  7. Participants window: names of other users for the same language.
  8. Boost speech-to-text suggestions: if you need to correct word(s) repeatedly, you can also press the ‘Boost’ button next to your correction. This will send your correction to the speech-to-text service, to increase the likelihood that they will be recognized.

Using the Correction Room

After receiving the link to the Correction Room, a user should follow these steps:

1) Copy the link to your browser (preferably Firefox) to go to your room.

The Correction room interface before connection

2) Press the Connect button: Clevercast will ask you to fill in your name for the text chat. Other users and event managers will see your name in the ‘Other Participants’ dialog.

When you press ‘Connect’ a popup will ask you to fill in your name

3) After filling in your name, you will be connected. You should now see green check marks for both captions and text. When the video broadcast is started, your video will automatically start playing.

The text chat can be used to communicate with other users for the same language or the managers of your event. On the right side, you can see other users of your transcription room.

The correction process

To begin correcting a caption, just click on a caption and start typing. The currently focused caption will be visually highlighted.

Once a caption-box appears, you have 30 seconds to make corrections. After 30 seconds, the box is grayed out and its text is used as a closed caption.

The caption correction interface supports the same basic text editing techniques familiar to word processors. Double click to select a word, triple click to select a sentence. Basic visual formatting is also supported, with Ctrl + B for bold and Ctrl + I for italic, and Ctrl + U for underline.

  Mac Windows
Next caption Tab Tab
Previous caption Shift + Tab Shift + Tab

Quickly editing words

  Mac Windows
Move cursor to beginning of current or previous word Option + (left arrow) Ctrl + (left arrow)
Move cursor to end of current or next word Option + (right arrow) Ctrl + (right arrow)
Delete previous word Ctrl + Option + Delete Ctrl + Backspace
Delete next word N.A. Ctrl + Delete
Select all text Cmd + A Ctrl + A


  Mac Windows
Bold Ctrl + B or Cmd + B Ctrl + B
Italic Ctrl + I or Cmd + I Ctrl + I
Underline Ctrl + U Ctrl + U

Boosting speech-to-text suggestions

After making a correction, the original word(s) and your correction are shown at the bottom left. When you press the ‘Boost’ button next to it, your word(s) are sent to the speech-to-text service. This increases the probability that your word(s) will be recognized over other similar sounding words or phrases.

Typical uses are to improve recognition of names and domain-specific vocabulary. Consider adding the names of speakers, the event, your company or organization, as well as technical words and phrases.



We recommend a recent computer, preferably high-end or at least mid-range with a fast processor and sufficient memory (e.g. Intel i7 with 16GB RAM) and a dedicated sound card and graphic card.


The operating system doesn’t matter. It should only be able to run a recent version of the Mozilla Firefox browser (make sure to install the latest update).

We recommend using Firefox. Other browsers with WebRTC support, like Google Chrome, should also work, but we recommend using Firefox for a number of reasons:

  • We use Firefox ourselves for testing.
  • Google Chrome is more commonly used for everyday browsing. There is a higher chance of add-ons being installed that could affect performance.

If for some reason a translator can’t use Firefox, you could try using Google Chrome instead.


To listen to the incoming audio, we recommend using a professional headset.

Fast and stable connection to Clevercast servers

A wired internet connection is required for audio translation. A good wireless connection could suffice for transcription. But we still recommend using an ethernet connection if possible, since it will ensure that the connection will remain fast and stable during the entire event.

Users need a fast and stable internet connection to the Clevercast streaming servers located in the Netherlands.

To test this, you should receive a link to the Translate@Home Connection Test page from your project manager. This way, you can test the quality of your connection in advance.

After receiving the link, open your browser (close all unnecessary other applications) and paste the test link in the address bar. The test page will ask you to enter your name, email and location and press the Start button. The browser will establish a connection with Clevercast and start sending data packets for about 30 seconds.

The ‘T@H Connection Test’ page

After 30 seconds, the test ends and you will see a popup with the result. The details of your test will also be made available to your project manager.

Sufficient bandwidth

Users should have a bandwidth of at least 5 Mbps down. If you're not sure, make sure to test beforehand or check your available bandwidth by going to Click on the Change Server link and type ‘I3D’ in the popup dialog and select ‘Rotterdam –’. Finally, press the GO button and wait until all tests are completed.

1) Click on the ‘Change Server’ link

2) Type ‘I3D’ in the popup dialog and select ‘Rotterdam -

3) Press the ‘GO’ button and wait until all tests are completed.

The Download Mbps value should be higher than 5 Mbps, otherwise you may experience difficulties in watching the original video + audio stream.

The PING and Upload Mbps value are less important (the Translate@Home Connection Test provides sufficient info).

Best practices

Make sure the latest Firefox version is installed

Do this before you start testing. Then go to the translator room and check if you can connect to video, audio and chat.


  • The OpenH264 video codec (offered by Cisco Systems, Inc) should be enabled in the Firefox plug-ins. This is the case by default. If you can’t see the video in Firefox (black screen) this plug-in is probably not enabled. Try enabling it or do a fresh install of Firefox.
  • If you are unable to use Firefox and you have a high-end computer, you can also use Google Chrome (after testing).

Restart your computer and close all other applications

To make sure your computer is stable, restart it before translating. When you’re ready to start, close all unnecessary applications to prevent them from using your processor, memory or internet connection. Make sure the Operating System is not allowed to start or download automatic upgrades.

Don't use multiple browser tabs

Avoid opening rooms in multiple tabs. This can result in problems with your connections or audio quality.

Test extensively

Make sure to test beforehand with a stream that has comparable audio settings. While you’re testing, the event manager should listen and help you to set the volume of your microphone.

Reconnect if a connection problem persists

If a problem (e.g. local network issue) occurs during the event, the audio of your translation will restore itself in most cases. If it doesn’t, you should quickly reconnect (press the disconnect button and then connect again).