Quality-Defined Variable Bitrate (QVBR)

What is Quality-Defined Variable Bitrate (QVBR)?

To address the shortcomings of traditional Constant Bitrate (CBR) and Variable Bitrate (VBR) rate control modes, AWS Elemental created Quality-Defined Variable Bitrate, or QVBR, a content-conscious version of VBR bitrate control.

QVBR analyzes every macroblock, frame, and scene in the video source, and automatically allocates bits to address information differences: higher bitrate use during complex video segments, and lower bitrate use during less complex video segments.

The result: an enhanced version of variable bitrate control that minimizes wasted bits and scales video bitrate to maintain consistent video quality.

How QVBR bitrate savings and benefits stack up for video providers:

  • Reduces video output bitrates up to 50 percent
  • Saves video content storage and delivery costs: No wasted bits
  • No additional cost to use with AWS Elemental encoding software and media services
  • Easy operation: Choose one setting for any type of source content
  • Quick start: Player changes not required
  • Built into encoder: No latency or extra analysis pass
  • Multi-codec: Use AVC or choose HEVC for further compression savings
  • Works for live video (events or 24/7 channels) and VOD applications: Broadcast, OTT, streaming, download, and more
  • Mix and match CBR, VBR, QVBR renditions in the same ABR set
  • You see dramatic improvements in video encoding efficiency and video encoding quality
  • Your customers receive a superior and consistent viewing experience

Validating the Design: Putting QVBR to the Test at AWS re:Invent

Each year, viewers around the world experience re:Invent keynotes through live streams. As with most large live events, AWS invests in high-quality visuals, production tools, and artwork to convey important information. With keynote presentations displayed on colossal screens seen by thousands of attendees in person, and many more via live streams, the viewer experience must be picture-perfect.

At re:Invent 2018, the team switched to QVBR for live streaming, and with additional AWS Elemental and AWS services delivered a more seamless viewing experience for a much lower cost. How much lower?

While the viewing audience for live keynotes grew significantly in 2018 compared to the previous year, the overall price of streaming dropped by more than 20 percent.

In sum, if AWS can use QVBR to reduce live streaming expenses at re:Invent, you can use QVBR anywhere you need to reduce storage and delivery costs and maintain consistent video quality.

Learn more: Get technical tips from an AWS Event Technology Team expert, such as how to use QVBR with your live or on-demand video, and how to choose the right QVBR quality level.

What Specific Video Quality Problems Does QVBR Solve?

If the most important characteristic of encoded video is quality, a simple and certain way to achieve it is through quality-defined variable bitrate (QVBR) control which is designed to deliver constant video quality and waste zero bits in the process.

In other words, when your video quality requirements are high, but your bandwidth budget is low, QVBR fulfills both needs. AWS Elemental software includes QVBR with no additional license fees.

Meeting video quality requirements is an ongoing challenge. Information contained in encoded video is inherently variable: different content and scenes carry varying amounts of information in each video frame. QVBR is rate control that automatically adjusts to the differences, and solves the problems of inconsistent video quality caused by video complexity.

QVBR also eliminates the guesswork and frustration of managing your “bits budget”: When video scenes are more complex, QVBR spends bits to maintain desired video quality levels. When video quality levels are reached, QVBR saves bits.

In the process, QVBR also saves you up to 50% of the costs you would otherwise need to allocate for both CDN egress and storage.

QVBR puts an end to video quality inequalities: It supports the AVC and HEVC codecs, your viewing audience enjoys a consistent experience, and you enjoy the most cost-efficient method of providing it.

How Does Quality-Defined Variable Bitrate Improve Video Quality?

Constant Bitrate Challenges

AWS_Elemental_QVBR_Diagram_CBR

How constant bitrate affects video quality:

  • Using bits when not needed, because you've already met video quality requirements
  • Not having enough bits when needed, resulting in lower video quality
  • Different types of content require different bitrate choices
  • Operator must take a best-guess approach when selecting the bitrate

How variable bitrate affects video quality:

  • Encoder uses as many bits as required to hit average bitrate, even if not needed for video quality
  • Operator needs to pick the average bitrate per asset
  • Selecting average to peak ratio is not straightforward
  • Different settings needed for different content types
  • Can’t get to optimal bit savings unless you encode multiple times and iterate to get lowest bitrate required by asset
AWS_Elemental_QVBR_Diagram_VBR

QVBR: No Bits Wasted = Big Bits Savings

AWS_Elemental_QVBR_Diagram_QVBR

How QVBR benefits video quality:

  • Variable bitrate control that automatically adjusts to different kinds of content and scenes
  • Encoder automatically adjusts actual quantization
  • Built on statistics developed for perceptual encoding such as AQ, MD, and RC
  • Save bits when quality level is reached (don't use what you don't need)
  • Use more bits to maintain quality level for complex scenes get

The Video Quality Advantages of QVBR

  • Saves costs: Less transfer with CDN egress and less storage, 10%-50% or more, depending on video content
  • Improves video quality (VQ) consistency: Maintain uniformity across all your content, and use a higher peak bitrate only for complex scenes
  • Supports AVC and HEVC codecs, for even greater compression efficiency
  • Easy operation: No more content-based bitrates. Instead, set a fixed video quality level and a max bitrate (according to connectivity and device requirements). The encoder does the rest
  • Achieves the same level of density, with no drop in performance
  • Works with both 1-pass encoding for live video (or faster turnaround VOD encoding), or two-pass encoding for additional processing
  • No additional licensing fees for the best video quality assurance tool available

How QVBR Makes Managing Video Quality Easy

  • Just upgrade and then enable, and start realizing savings and video quality improvements immediately
  • As AWS Elemental continues to improve video quality, enabling new features can boost video quality and improve consumer experience using the same bitrate or less
  • Useful for both live and VOD workflows in a variety of applications
  • Generate consistently high video quality, save space to reduce transfer and storage costs, and configure easily
  • Because AWS Elemental develops its own encoding algorithms, video quality features are part of the software – no external tools or processing required
  • Adapts frame by frame to maintain video quality
  • Before: Maximum video quality per frame. Now: minimize the bits used based on video quality specs that the user selects

Quality-Defined Variable Bitrate (QVBR) Encoding Demo

Win on video quality + cost. AWS Elemental Quality-Defined Variable Bitrate control lets you set encoding video bitrates according to quality, and save up to 50% on storage and delivery costs in the process. Learn how fast and easy QVBR is to set up, configure, and use in this demonstration. 

Quality-Defined Variable Bitrate (QVBR) Encoding Demo [11:23]

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