The quality expectation levels for mobile live video users are also increasing. They expect the same type of experience on their mobile devices of live video as they receive in their home televisions. They demand minimal stall, high-quality video, minimum delay and a short loading time. It is clear that quality of service (QoS) needs to be ensured in order to maintain audiences for mobile live products. Broadcasters know this scenario very well, and now all OTT providers must deploy solutions that guarantee the kind of QoS that terrestrial broadcasters have delivered, for decades.

Solving The Latency Problem

But there are critical prerequisites that confront content providers in this era of real-time mobile video: low latency and synchronization. Current live video services are not actually live, as there is delay from the broadcast origin to end users. What is more, users receive the same scene at different timelines. People watching the same soccer game on their cell phones scream joyfully at the score, but that event is happening at least 30 seconds after the crowd in the arena already chilled out. What is more, the shouting time of each people differs according to network condition or device performance.

To solve the latency and synchronization issues in live video streaming on mobile, HECAS developed its HECAS MLS (Mobile Live Streaming) solution based on MPEG Media Transport (MMT). This mobile video streaming solution offers ultra-low latency, efficient video transmission, and perfect playback synchronization. This enables video hosts to deliver their mobile live video faster and simultaneously to end users. And most importantly, video transmission is scalable to broadcast-size audiences.

MMT, specified as ISO/IEC 23008-1 (MPEG-H Part 1) standard, was adopted in order to achieve ultra-low latency and a fast start. MMT uses Media Processing Unit (MPU; small media chunks) to deliver media, enabling faster video playback when compared to MPEG-DASH/HLS based streaming. With HLS-based lived video streaming, delay first occurs when generating a chunk, and then another delay takes place during the process of the chunk loading upon the request of the client.

However, MLS enables fast start by instantly delivering MPUs generated from the video element stream. With this mechanism, end-to-end latency is reduced to less than 3 seconds in a commercial 4G network environment in South Korea.

Bandwidth Efficiency

Mobile live streaming based on MMTP enables efficient data transmission. When watching a mobile video with Netflix quality for an hour (512Mb), the technology demonstrated a 10% data reduction when compared to streaming based on MPEG2-TS, where the packet length is fixed, which means part of the data payload is wasted.

MMTP, however, uses a variable length transmission so that MPU payload is fully utilized. HECAS MLS stream is adjusted to the Maximum Transport Unit (MTU) size of the specific network carrier. This enables users to watch more videos within their limited data plans. In addition, Forward Error Correction (FEC) is not used, for the purpose of data saving.

When FEC is applied to a mobile environment, the heat of the smartphone, the enormous battery drain, and the user’s data consumption are increased. To solve this problem effectively, a method of recovering a lost packet using Automatic Repeat reQuest(ARQ – also referred to as Automatic Repeat Query) message is used.

Staying Synchronized

Synchronization is another important factor in interactive TV shows and live sports. When content includes interactive features such as live chat, all users must be at the same time flow. The Universal Time Clock (UTC) of the MMT standard is used in synchronizing the time between the server and the device. Video play speed is adjusted to consider the packet delay time of the client. The playback difference of the HECAS MLS solution is less than 30 milliseconds between multiple devices in national coverage in a commercial network environment in South Korea. When considering that a second of regular video is comprised of 30 frames of image, the synchronization can guarantee what is considered to be a perfect real live experience.

Track Record

The HECAS MLS solution has been commercially implemented on Korea’s leading telecom operator SK Telecom (SKT) since May, 2016. HECAS MLS is deployed on the SPOTV live sports channel of SKT Oksusu mobile TV service. For content providers and distributors, the ultimate live video experience is achievable with ultra-low latency, efficient data transmission, and perfect playback synchronization. With real live video, mobile users can fully enjoy more abundant interactive media complete with such features as interactive live chat, real-time auctions, premium sports events and other new business opportunities not previously feasible.