1 VAS Intro

1.1 Brief Introduction

Many on-line video platforms provide the feature of transcoding, which is to convert HD (high definition) streams of high bitrate and high resolution into video streams of low bitrate and low resolution, adapting the viewers’ network environment. However, converting from high bitrate and resolution to the low will reduce the video quality, and therefore affect users’ viewing experience.

In response to this situation, CDNetworks rolls out LBHD (Low Bandwidth High Definition), which is a video transcoding technique aiming to reduce stream bitrate while guaranteeing user’s optimal viewing experience. Instead of having a fixed bitrate, the video will have a LBHD bitrate which changes automatically during playback.

LBHD saves a lot of bandwidth cost for our customers through automatic bitrate adjustment, which reduces bitrate on the basis of video content, without compromising the original image quality. Meanwhile, LBHD also improves the user experience by performing image sharpening with the transcoding technique developed by CDNetworks.

1.2 Applicable Product Line

Media Acceleration-Live Broadcast

1.3 Application Scenario

This feature is applicable to the scenarios of interactive live show, gaming, sports, short video, online education, etc.

2 VAS Detail

2.1 VAS Description

In the perspective of technology, CDNetworks Live LBHD reduces the bitrate in a rational manner without comprising use-perceived image quality; and enhances the image while keeping the bitrate unchanged. In conclusion, CDNetworks Live LBHD is realized through by-scene transcoding, encoder optimization and image quality rebuild.

(1) Scene Recognition

A complete video playback process involves ingesting, encoding, transmission (distribution), decoding, and playing. CDNetworks LBHD is to transcode the video stream during the CDN distribution process, analyze the video content before re-encoding, set rational encoding parameters according to video scenes while ensuring the lossless image quality, and reduce bitrate while ensuring the image quality to the greatest extent.

(2) Lossless Bitrate Reduction

To enhance users’ visual experience, CDNetworks has achieved the following two features through encoder optimization:

• Rational bitrate allocation. The bitrate will be allocated to the desired part, thus enhancing viewing experience.
• Texture enhancement. Conduct operations including sharpening, noise reduction, comparison enhancement, deblocking for the elements (such as Logo and text) to which the visual system is sensitive.

(3) Image Quality Rebuild

With the Resolution Rebuild technology, video source damages such as camera shake and distortion after transcoding will be repaired, enhancing the user experience when the file source is in low quality.

2.2 Service Access Instructions

CDNetworks LBHD will be applied when requested by the user. If end users request for the LBHD-processed live stream, LBHD processing will be triggered; if not, the processing will not be implemented. The on-demand access of LBHD facilitates the seamless access of video platform without any structure adjustment.
Request method for CDNetworks LBHD:
The request from player will trigger LBHD processing.
Normal live streaming request: http://www.test.com/live/channel.flv;
LBHD live streaming request: http://www.test.com/live/channel_nb.flv
Note: Negotiate with the customer when deciding the suffix of “nb”.

2.3 Usage Instructions

The following items shall be confirmed when enabling Live LBHD:

1. Confirm the URL format of requests initiated by the player;
2. Confirm whether to use the maximum bitrate limit automatically. If not, confirm the maximum bitrate limit with the customer. For example, bitrate shall not exceed 3Mbps for 1080P, and 1.5Mbps for 720P.
   3 Notices
3. The enabling of Live LBHD might increase live streaming latency by 1-2s.
4. Live LBHD processing only works when the input is a stream. For example, the processing will take effect when the input is in RTMP/HTTP FLV/HTTP TS, and will be invalid when the input is in HLS/HDS.