Building a Group Video Calling Service Inside a LINE App with AI, Without a Web Engineer (opens in new tab)

LINE’s LIFF enables web services to run directly inside the LINE app, turning a LINE Official Account into an interactive service platform rather than merely a notification channel. The LINE Planet team demonstrated this by building a group video-calling service with only a PM and an Android engineer, without a web engineer. The core architecture combines a LIFF web app, a small token-issuing app server, and LINE’s managed authentication and WebRTC infrastructure.

Services Enabled by LINE OA and LIFF

• Professional consultations: One-to-one video sessions with lawyers, financial planners, counselors, and other experts.
• Remote education: Scheduled video lessons with separate rooms for multiple teachers and students, including screen sharing.
• Interactive live broadcasts: Events for 500 to 10,000 simultaneous participants, including audience members joining conversations as panelists.
• In-game voice chat: Real-time communication with LINE friends without switching to another app.

Overall Architecture

• LIFF provides the in-app web interface and automatically exposes LINE login information such as userId and displayName.
• LINE Planet handles WebRTC media processing and global network infrastructure.
• The web app uses the LINE Planet SDK to implement the group call experience.
• The app server issues LINE Planet access tokens.
• Firebase Cloud Functions can provide the app-server layer without managing separate server infrastructure.
• The developers are responsible mainly for connecting these components; LINE handles authentication, media transport, and much of the underlying infrastructure.

Required Preparation

• Use Node.js 20 LTS or later with npm.
• Deploy over HTTPS; local development can use ngrok.
• Create a Business ID, developer account, and Provider in the LINE Developers Console.
• Create a LINE Official Account and enable its Messaging API.
• Create a LINE Login channel under the same Provider and register a LIFF app.
• Record the LIFF ID because it is required for initialization.
• Set the LINE Login channel to Published for the shareTargetPicker API, which supports inviting LINE friends.
• Request a LINE Planet Console account and service ID from the LINE Planet team.

Designing and Generating Room IDs

• LIFF can collect call setup information and register it with the app server, reducing the amount of pre-call configuration.
• Users can join simply by entering or following a room ID.
• The example generates a random 16-character alphanumeric ID using crypto.randomUUID().
• If a roomId query parameter exists in an invitation link, the app restores and uses that room instead.
• The same design can later support fixed rooms based on interests or automatically generated rooms for user groups.

Building the Preview Screen

• The preview screen lets users check their camera and microphone before entering a call.
• Instead of directly calling getUserMedia, the example uses PlanetKit’s MediaStreamManager.
• A single MediaStreamManager instance is reused from preview through the conference, avoiding repeated permission requests.
• Camera input is created with createMediaStream() or replaced with changeVideoInputDevice().
• Microphone muting changes the audio track’s enabled flag, preventing another permission prompt in mobile webviews.
• Mobile users can switch between front and rear cameras by resolving the appropriate device ID.
• The sample UI includes camera and microphone toggles, camera-flip controls for mobile devices, and an “Enter” action.
• The article notes that the sample focuses on the essential flow; production applications still need stronger security, error handling, and performance optimization.

The practical recommendation is to treat LIFF and LINE Planet as managed building blocks: implement the web call interface and a minimal token server, while relying on LINE for user identity and PlanetKit for real-time media.