This is a pretty exciting day for all of us working on HD Photo.  Today, the Joint Photographic Expert's Group (JPEG) announced a new work item for the standardization of a HD Photo as a new file format called JPEG XR (XR is short for "extended range".)  You can read the full details in the Microsoft press release here and the JPEG press release here.  (Go ahead and check it out; we'll wait here.)

Wow!  Our group at Microsoft's Core Media Processing Team has been working on HD Photo for over five years.  The underlying compression technology is based on work from Microsoft Research that goes back even farther than that.  Since our first public disclosures about "Windows Media Photo" (the original name of HD Photo), our goal has been to develop the ultimate successor to JPEG as the format of choice for all digital photography.  We also announced earlier this year that we were committed to standardizing HD Photo as an open format.  With today's announcements, we're moving a lot closer to both of those goals.

An Illustrious History

For as long as digital photography has existed, digital photos have been defined by the technology created by the JPEG Committee, and it has become the most widely used standard in the world.  Simply put, digital photography would have never been possible without the work of Joint Photographic Experts Group and their JPEG image compression technology. 

Over the years, the JPEG format has become ubiquitous.  Every application, device or service that is in any way related to digital photography recognizes and/or produces this format.  JPEG is digital photography.

But for all the value the original JPEG format delivers, it's starting to show its age.  Limitations of the JPEG file format are hindering the ability to innovate new features and quality improvements in digital photography.  There have been multiple approaches to work around these limitations, but we need significant improvements to the industry standard photo format to enable new opportunities for innovation and market growth.

JPEG 2000 introduced several excellent innovations, but it largely addresses requirements beyond the role of the original JPEG format.  So, while JPEG 2000 is making some valuable contributions in other areas of digital imaging, this advanced format doesn't directly address the key requirements for consumer and professional digital photography.

A New Format for Digital Photography

From the beginning, Microsoft designed HD Photo to meet the specific needs of end-to-end consumer and professional digital photography, and address the current limitations of the original JPEG format.  HD Photo offers new pixel formats to retain higher image quality, great new progressive decoding features for more powerful image access and manipulation, and significant compression improvements to improve quality, reduce file sizes and enable better performance.

The use of the original JPEG format for digital photography has been limited to 24-bit images; each pixel is made up of three colors (red, green and blue), each stored as an 8-bit value.  This allows 256 different values for each color, or 16.8 million possible colors.  While that sounds like a lot, it significantly limits the ability to create the highest quality images.  Camera sensors typically capture up to 68.7 billion colors, so when saving as a JPEG file, a lot of information has to go.  Additionally, during any image editing operation, a much greater range of colors is required to preserve information that would otherwise exceed the finite limits of the color range.  Once data is lost beyond these limits, it can't be recovered in the future.

HD Photo offers a wide range of pixel formats at 8, 16 or 32 bits per channel including high dynamic range wide gamut formats using fixed point or floating point representations.  HD Photo offers options that eliminate the quality limitations of the original JPEG format's lone 24-bit pixel values.  This previous blog post shows just one example of the capabilities enabled by HD Photo's new pixel formats.

HD Photo's progressive decoding architecture makes it possible to efficiently decode a the image at a lower resolution, reduced quality, or a selected region by processing only a portion of the entire compressed file.  Progressive decoding enables a whole bunch of very cool features.  The Photosynth Technology Preview from Microsoft Live Labs is an excellent example of the new class of applications powered by progressive decoding.  Photosynth is discussed in some detail in a previous blog post here.  HD Photo also helps power Virtual Earth 3D and Microsoft Lab's HD View Giga-pixel Image Viewer.

HD Photo delivers state of the art image compression, offering up to twice the compression efficiency of original JPEG format (providing the same quality in half the file size) as well as higher quality lossy compression that scales all the way to mathematically lossless compression.  This makes it possible to use higher bit depth pixel formats for better image quality while retaining similar file sizes.  Better compression also allows for much smaller files using traditional 8-bit pixel formats.  Smaller files can be saved and transferred faster, providing longer device battery life and an improved user experience.  HD Photo delivers this improved compression using a high performance algorithm that is equally at home on low cost, low power devices or high end multi-core PC's.

An Open Standard

The path towards standardizing HD Photo began earlier this year, and now becomes public with today's announcement from the JPEG Committee.  This is one more step in an ongoing process towards our stated objectives for standardization.  Our goal is that HD Photo becomes JPEG XR, an open standard under the complete control of the JPEG Committee, with royalty-free rights to all required patents granted by Microsoft.  Microsoft is actively participating with the JPEG Committee to produce a complete and detailed technical specification enabling anyone to create implementations in any programming language, on any platform and under a wide variety of business models.  We're excited to be contributing to the next great standard for digital photography, enabling a whole new level of feature and technology innovation, improving photo quality and creating exciting new applications and services.  It's our sincere hope that that today's announcement will help accelerate the process of making HD Photo (JPEG XR) as ubiquitous as JPEG is today. 

Bill Crow
HD Photo Program Manager