AVIF for Next-Generation Image Coding

Netflix Technology Blog
17 min readintermediate
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Overview

The article discusses the AV1 Image File Format (AVIF) as a next-generation image coding solution that offers superior compression efficiency compared to traditional formats like JPEG. It highlights Netflix's efforts in implementing AVIF for their image assets, showcasing the benefits of this format in terms of quality and file size reduction.

What You'll Learn

1

How to implement AVIF for image compression in applications

2

Why AVIF is a better alternative to JPEG for modern applications

3

How to evaluate image codecs using the open-source comparison framework

Prerequisites & Requirements

  • Understanding of image compression concepts
  • Familiarity with Docker for using the comparison framework(optional)

Key Questions Answered

What are the advantages of using AVIF over JPEG?
AVIF provides better compression efficiency, allowing for smaller file sizes without significant loss of quality compared to JPEG. This is particularly beneficial for applications that require high-quality images while minimizing bandwidth usage, making it ideal for streaming services like Netflix.
How does Netflix utilize AVIF for image assets?
Netflix employs AVIF to compress image assets for its user interface, ensuring that images maintain high quality while reducing the data required for storage and transmission. This is crucial for delivering a rich visual experience across various devices.
What is the image compression comparison framework mentioned in the article?
The image compression comparison framework is an open-sourced Docker-based tool developed by Netflix that allows users to compare the performance of various image codecs, including AVIF. It enables easy reproducibility of results and control over target quality ranges.
What datasets were used to evaluate AVIF's performance?
The evaluation of AVIF's performance was conducted using public datasets like Kodak and internal datasets from Netflix, including boxshots and billboard images. These datasets help in assessing the codec's efficiency across different image types and resolutions.

Key Statistics & Figures

Compression factor of AVIF compared to JPEG
59x
This factor was observed when comparing a JPEG 444 image at 20,429 bytes to an AVIF 444 image at 19,788 bytes.
Compression factor of AVIF for another image
282x
This was noted when comparing a JPEG 444 image at 13,939 bytes to an AVIF 444 image at 4,176 bytes.
Compression factor of AVIF compared to JPEG in another instance
29x
This was observed when comparing JPEG 444 at 40,276 bytes to AVIF 444 at 39,819 bytes.

Technologies & Tools

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Image Format
Avif
Used for compressing image assets at Netflix to improve efficiency and quality.
Tool
Docker
Used for the image compression comparison framework to facilitate codec testing.

Key Actionable Insights

1
Implementing AVIF can significantly reduce image file sizes while maintaining quality, which is essential for optimizing web performance.
This is particularly important for applications that rely heavily on images, such as streaming services, where bandwidth savings can lead to improved user experiences.
2
Using the open-source image compression comparison framework can help developers make informed decisions about which codec to use based on specific quality metrics.
By leveraging this framework, developers can easily experiment with different codecs and configurations to find the best fit for their application needs.
3
Understanding the implications of color subsampling can enhance image quality in compressed formats.
Choosing the right subsampling technique, such as 420 over 444, can lead to better performance in terms of file size without compromising perceived image quality.

Common Pitfalls

1
Relying solely on PSNR as a quality metric can lead to misleading results in image quality evaluation.
While PSNR can indicate closeness to the original image, it does not correlate well with perceived quality across a wide range of compression levels. This can result in overspending bits without achieving the desired visual fidelity.

Related Concepts

Image Compression Techniques
Comparison Of Image Formats
Impact Of Color Subsampling On Image Quality