Low latency live (LL-HLS)
This document is a machine-translated draft and is currently undergoing review. Some content may be inaccurate or differ from the original Korean version. For the most precise information, please refer to the Korean documentation.
As content that emphasizes real-time two-way communication continues to grow, reducing streaming latency has become a key competitive advantage for services.
Kollus Live has adopted the LL-HLS(Low Latency HLS) method based on CMAF(Common Media Application Format), dramatically improving latency from the previous ~20 seconds to 3–8 seconds. This provides users with a more dynamic real-time experience while maintaining the stability of existing infrastructure.
Standard live vs low latency live comparison
The two methods differ in transmission efficiency and feature support, so you should choose the method that fits your service's purpose.
| Item | Standard live (Standard HLS) | Low latency live (LL-HLS) |
|---|---|---|
| Latency | ~20 seconds | ~3–8 seconds |
| Playback method | Playback after full segment download | Segment divided into 0.5–2 second chunks for immediate playback |
| Media format | TS (Transport Stream) | fMP4 (CMAF) |
| Network stability | High (resilient to network fluctuations) | Moderate (sensitive to network quality) |
| Security | Supported (AES-128, Multi DRM available) | Not supported (DRM not applicable) |
| Timeshift | Supported | Not supported |
| Player compatibility | Standard HLS player | LL-HLS player |
- Buffering caution: Low latency live minimizes buffering to reduce latency. Therefore, if a user's network is unstable, buffering may occur more frequently than with standard live.
- Unsupported features: DRM and timeshift features are not supported in low latency live mode.
Key features and recommended use cases
Key features
- Low latency: Optimized for real-time interactions such as live commerce with response times within a few seconds.
- Compatible with existing infrastructure: As an extension of the standard HLS protocol, it can leverage existing CDN environments as-is.
- Adaptive Bitrate(ABR) support: Maintains the ability to automatically adjust video quality based on the user's bandwidth while keeping latency low.
Recommended use cases
- Live commerce: When real-time Q&A and event participation between hosts and users are required
- Online education: Educational broadcasts where real-time Q&A between instructors and students is important
- Sports/Entertainment: Broadcast services that need to deliver the energy of live events in real time
Technical principles: CMAF-based LL-HLS
LL-HLS maintains the structure of standard HLS but processes data in smaller pieces to reduce transmission wait time.
Key components and how it works
| Component | Description |
|---|---|
moof / mdat | Container structure for media data. Separates moof (header information) and mdat (actual data) to process quickly in small units. |
| Chunk | Divides a single segment into small chunks in millisecond (ms) units, allowing the player to start playback before the entire file is complete. |
| Preload Hint | Provides hint information so the player can predict and request the next incoming data piece in advance, improving response speed. |
Pre-check list
Supported OS and browser specifications
Low latency live (LL-HLS) uses the latest streaming standards, so an environment meeting at least the minimum specifications below is recommended for stable viewing.
Recommended operating systems
| Operating system | Minimum supported version |
|---|---|
| Windows | 10 or later |
| macOS | 10.11 or later |
| iOS | 17.1 or later |
| Android | 7.0 or later |
Recommended browsers
| Browser | Minimum supported version | LL-HLS support status |
|---|---|---|
| Chrome | 70 or later | Optimized playback support |
| Safari (macOS) | 13 or later | Native LL-HLS support |
| Safari (iOS) | 14 or later | Stable support in mobile environment |
| Edge (Chromium) | 80 or later | Same level of performance as Chrome |
| Firefox | - | Limited support (not recommended) |
If users access from environments below the recommended specifications, the system detects this and automatically switches to the standard live (Standard HLS) method. Therefore, users on older environments can still watch live without interruption.
Encoder configuration recommendations
Precise configuration at the encoding stage is essential to maximize the efficiency of low latency live.
Keyframe interval
- Recommended setting: 1s
- Description: Fixing the keyframe interval to 1 second aligns the length of video and audio segments. This facilitates synchronization at the partial segment (chunk) level, which is the core of LL-HLS, greatly improving playback stability.
- Caution: If the interval exceeds 1 second, audio/video sync may be off, or frequent buffering may occur in the player.
CPU usage preset
- Recommended setting:
veryfast - Description: The optimal preset that maintains consistent quality while reducing CPU load during real-time encoding. Reduces resource consumption on the streaming server, ensuring stable streaming even during long broadcasts.
The recommended settings are standard options widely used in FFmpeg or x264-based encoders (OBS, vMix, etc.). The actual application method and optimization effect may vary depending on the type of encoder or software version.
Low latency live setup procedure
The low latency live feature can be easily applied simply by specifying the type when creating a channel.
- Click Kollus Live console > [Channel] > [Channel list] > [Register channel] in the upper right corner of the screen.
- Set [Type] to [Low latency live].
Refer to the document below for how to create a channel.
Frequently asked questions (FAQ)
Q. Can low latency live be viewed on all operating systems and browsers?
Most modern environments support it. If a user's environment does not meet the LL-HLS recommended specifications, the system detects this and automatically switches to the standard live (Standard HLS) method for playback, so there is no issue with viewing itself.
Q. Is Multi DRM supported for low latency live(LL-HLS)?
Multi DRM is currently not supported for low latency live(LL-HLS).
Q. Can standard HLS and low latency live(LL-HLS) be operated simultaneously?
Yes. Kollus Live supports a hybrid configuration that selects the optimal method based on the user's device specifications. It provides low latency streaming for supported environments and standard streaming for other environments, ensuring a stable experience for all users.
Q. What is the biggest change users experience when low latency live is applied?
The time lag between broadcast streaming and user reception is dramatically reduced. In particular, it is highly effective for content where immediate interaction between hosts and users is important, such as real-time chat, quizzes, and live commerce.
Q. Must the recommended encoder settings be followed?
Yes, a keyframe interval of 1 second and the veryfast preset setting are strongly recommended to ensure stable low latency quality.
Incorrect settings can cause audio/video sync issues or frequent buffering.
Q. Can latency be reduced to below 1 second?
Theoretically possible, but considering the variability of actual internet environments and CDN transmission stability, 3–8 seconds is the most stable range for maintaining uninterrupted broadcasting.