HD Photo Device Porting Kit Readme

Release notes for the HD Photo Device Porting Kit

Windows Media Photo Is Renamed HD Photo

This Device Porting Kit supports the still image format previously released under the name Windows Media Photo.

Throughout the development of the HD Photo still image file format, the project was first known (internal to Microsoft) by its code name "Photon." Throughout its beta release, and when publicly introduced at WinHEC 2006, the file format was named "Windows Media Photo." With the introduction of the released version of the Device Porting Kit, the format name has been officially changed to "HD Photo."

"Windows Media Photo" is still used as the name for the Windows implementation of the "HD Photo" format, in both Windows Vista and the Windows Image Component (WIC) and .NET Framework 3.0 redistributable packages for down-level versions of Windows. "Windows Media Photo" may still be used internally with this release of the Device Porting Kit.

Windows Media Photo and HD Photo refer to exactly the same file format. There are no features or changes that differentiate one from the other. They are two names for the same format.

We have extended the specification to allow two different file extensions - either .wdp or .hdp - to be used to identify an HD Photo (or Windows Media Photo) file. With the 1.0 release of Windows Vista, only the .wdp extension is recognized. This will be updated at some point in the future. Applications that support the HD Photo file format should recognize either extension, and ideally offer the option to create files with either extension.

While we recognize the potential confusion and issues that this name change can create, we believe the new name, initiated in part based on feedback from our partners, provides a better identification for broad, cross-platform support for this new still image file format.

Device Porting Kit Contents

This Device Porting Kit contains documentation, reference source code, sample applications, and utilities for the evaluation and implementation of the HD Photo file format and compression technology.

If you have used a zip file utility to extract all the files to a single directory, stop now. Delete the files and run the self-installing executable file to install the individual files in the correct directory structure.

Assuming the installation dir is C:\HDPHOTO, all the paths mentioned below are relative to this base path.

The Visual Studio 2005 main solution is:

  • •Systems\tools\SampleCodeNew\WMPEncDecoder\WMP.sln

Build WMP.sln Debug Configuration, you will get:

  • Systems\tools\SampleCodeNew\WMPEncDecoder\Debug\WMPDecApp\WMPDecApp.exe
  • Systems\tools\SampleCodeNew\WMPEncDecoder\Debug\WMPEncApp\WMPEncApp.exe

The xplat subdirectory contains a UNIX and Linux compatible make file for building the encoder and decoder, including support for big-endian or little-endian processor architecture. It is the developer's responsibility to properly organize all the source files according to the paths defined in this make file for its correct operation. This is provided as a convenience for cross-platform developers and to demonstrate the correct operation of the encoder and decoder on big-endian systems.

"HDPhoto_Feature_Spec_1.0.doc" documents the file container format, metadata tags and Windows API's, and other general information about the file format.

"HD_Photo_Bitstream_Spec_1.0.doc" provides a detailed specification of the compression encoder and decoder algorithms plus the detailed structure of the compressed data (elementary) bit stream. This document is designed to be used in conjunction with the included source code. If you find instances where the code differs from the documentation, the code implementation should be used as the reference.

"HD_Photo_DPK_1.0.doc" documents the contents of this porting kit, the usage of the command line file conversion utilities (WMPEncApp.exe and WMPDecApp.exe), and technical details of the API's and data structures between these sample command-line applications and the core codec.

The code and documentation in this release represent the final design and specification of the 1.0 bit stream, and can be used as the reference for final implementations of encoders and decoders for HD Photo. This version corrects some bugs that were present in the previous RC version.

This release of the DPK has received extensive testing of all the various pixel formats, encoder options and modes of operation. We are confident that most errors and other bugs have been resolved. Any code bugs, documentation errors or other discrepancies found in this release candidate should be reported to Microsoft as promptly as possible. These can be submitted to hdphoto@microsoft.com.

This DPK provides basic support for big-endian architectures. We have successfully tested the encoder and decoder using a big-endian processor. This support is provided as a starting reference to be adapted to the specific platform and hardware architecture of the target system.

Contact Information

For any and all technical questions or feedback about any part of this Device Porting Kit, including the documentation, please send e-mail to:


We will respond as promptly as possible with answers to your questions.

Additional information, best practices, tools, utilities, sample code, sample image content, links to additional resources and community discussion can currently be found at http://blogs.msdn.com/billcrow.

- The Microsoft HD Photo Development Team

Change History

V.07 September 2005 First Beta Distribution

V.08 November 2005 Documentation Update

  • There are NO CHANGES to the bit stream. Files encoded with the 0.7 release of the porting kit are fully compatible with this release, and vice versa. However, due to various minor fixes, encoded bit streams may not match exactly between the two versions.
  • Major rewrite of the bit stream specification. This document is still not complete but this version contains significant improvements, including the removal of extraneous implementation information not relevant to the bit stream specification.
  • Updates to the feature specification including an important correction on the use of the encoder property parameters, using TIFF-compatible descriptive metadata tags, a significant correction to the formatting (which had caused chapters 2 & 3 to be inadvertently merged together), and numerous other minor corrections and clean-up.
  • Minor changes to the Porting Kit spec to sync with the other documents
  • A number of minor bug fixes to the codec code and a fix to the glue code to insure the encoder was writing correct metadata to the output file.

V.09 February 2006 Documentation Update, Bitstream Update, New Features

  • The bitstream has changed to accommodate new features, correct some inconsistencies and respond to feedback we have received to date. Files encoded with previous versions of the porting kit will not decode with this version of the decoder. Likewise, files encoded with this decoder will not decode with previous versions.
  • Significant expansion and improvements to the bit stream specification. This version should help answer a number of questions and more completely describe the algorithm and the associated bit stream elements.
  • The feature specification includes numerous corrections, plus updates describing the operation of the new compressed domain operations. These new features are still being finalized and have not had extensive testing at this time.
  • The porting kit spec has been updated to document the new command line options in the sample apps for compressed domain operations as well as to correct some other minor problems.

V1.0RC May 2006 Documentation Update, Bitstream Update, New Features, New Tools

  • There are a couple minor (but breaking) changes to the bit stream from v.09 to support some requested new capabilities. This is now the FINAL bit stream for Windows Media Photo Version 1.0. This version of the bit stream is compatible with the implementation of Windows Media Photo in Windows Vista Beta 2.
  • The Feature Specification was expanded to include a new chapter with detailed descriptions of the different numerical encodings, pixel formats and default color spaces supported by Windows Media Photo.
  • The specification for including an embedded thumbnail/preview was added to the Feature Specification. Numerous other changes, corrections and minor additions were also made to the feature specification.
  • Compressed domain transformation operations have been implemented.
  • Many issues with different pixel formats have been resolved. Most of these were bugs in the sample applications and did not require changes to the encoder or decoder.
  • Encoder and decoder support for big-endian architecture has been added. There is also a UNIX/Linux compatible make file for building the porting kit code on a big-endian processor.
  • The Porting Kit Spec has been updated to include updated documentation on the sample application command line options.
  • An unsupported utility to convert from compressed .hdr files to uncompressed .hdr files is included. Adobe Photoshop CS2 saves .hdr files in compressed mode only. This utility can be used to convert these to uncompressed mode, which is required by the wmpencapp utility. While we have tested this utility (we use it regularly for our own testing), we cannot offer any support if there are problems with its use.

V1.0 RTM November 2006 Name Change, Float/Alpha Fixes, Doc Updates, New Tools

  • Three separate problems with floating point pixel formats were identified and corrected, including a quantization bug, a problem with renormalization of the base and with the use of the block transform. This may result in changes to the compressed bit stream for floating point images, so any previously created images that use one of the various floating point pixel formats may need to be re-generated with this corrected version.
  • A problem with interleaved alpha channel encoding was fixed. Interleaved alpha channel images should now work properly.
  • The default restriction in the RC release that prevented certain tiling modes (to insure compatibility with Windows Vista Beta 1) has been removed.
  • The version code written to the header of the container has been changed from the development value of 00 to the release value of 01.
  • There were other bug fixes and cleanup work implemented throughout the code.
  • All documentation was updated to reflect the name change to HD Photo. Please note that to avoid unnecessary delays in releasing this version of the Device Porting Kit, no changes have been made to any code related to this name change. These changes will be integrated in a future release.
  • The Feature Specification was updated to describe the new name, provide information on additional meta data tags, clarify a number of sections based on feedback we have received, and correct a number of other minor typos and syntax problems.
  • The DPK Specification was updated to reflect the new format name, provide a more detailed description of the use of the sample applications (and describe the use of the various encoder parameters), document the new utility programs, and correct a number of other typos, errors, omissions and formatting issues.
  • The Bitstream Specification was updated to reflect the new format name, significantly expand and improve the technical description of the compressed bit stream, and correct a number of typos, errors and formatting issues.
  • WMPEncApp was enhanced to properly default the alpha mode and add support for setting the quality of planar alpha channels independent from the image quality.
  • A new utility, IMAGECOMP, was added for uncompressed image quality and difference measurements. While we have tested this utility (we use it regularly for our own testing), we cannot offer any support if there are problems with its use.

Send comments about this topic to Microsoft