What's New in DirectShow?

This article describes what's new in Microsoft® DirectShow®. The samples are now in the subdirectory Samples\Multimedia\DShow\Src\samplename. For information about new features, filters, samples, and interfaces, see the following sections.

New Windows Media Player Control

The Microsoft® Windows Media™ Player control contained in Msdxm.ocx is a Microsoft® ActiveX® control used to add multimedia playback to applications and Web pages. It provides a way to render a variety of network streaming and nonstreaming multimedia formats, including the streaming formats MPEG-1, MPEG-2, ASF (Advanced Streaming Format), VOD (Video On Demand), RA (RealAudio) version 4, and RV (RealVideo) version 4, and the nonstreaming formats AVI, MOV, MIDI, WAV, SND, and Indeo 5, among others. The Windows Media Player incorporates many of the features of the Microsoft® ActiveMovie™ control and the control for earlier versions of Windows Media Player, as well as many new features. You can use the Windows Media Player control in ActiveMovie mode. This enables you to use the new control as you did the old control.

For more information about the Windows Media Player, see the Windows Media Player control documentation.

Expanded MPEG-2 Support

DirectShow has two new filters and two new interfaces to support MPEG-2 applications. See the following topics for more information.

Support for Playing Video from Within Applications that Are Using DirectDraw Exclusive Mode

The IDDrawExclModeVideo interface enables games to play video while in Microsoft® DirectDraw® exclusive full-screen mode. For an example, see the DDrawXcl sample in the Samples\Multimedia\DShow\Src\DDrawXcl subdirectory. The IDDrawExclModeVideoCallback interface was added to enable applications to get synchronous notification about changes to the overlay position, size, visibility, and so on, so that the application can adjust its video visibility, size, and position.

Support for Dynamic Audio Format Changes

The previous release of DirectShow provided support for an audio format change only if it occurred on the first sample delivered. This restriction has been removed and audio format changes are now supported by the audio renderer filters at any time during playback. One point to note is that a transform filter downstream of the filter initiating the format change might need to be enhanced as well for this feature to work correctly at the graph level.

Additionally, this release fixes a problem where, for filter graphs that didn't provide audio data at the start of the run (for example, DVD and capture), a format change on the first sample caused audio to stop when the DSound Audio Renderer filter was used.

Changed Handling of Noncontinuous Audio Data

In previous versions of DirectShow, when a time gap occurred in audio data, generally this gap would be ignored because the audio renderer filter would continue the clock on the arrival of the first time stamp after the gap and cause a jump in the reference clock used by all filters for synchronization.

In this release, this behavior has been fixed for the DSound Audio Renderer filter. This filter now compares the time stamp at the beginning of a new sample with the time for the end of the previous sample and will attempt to fill the gap with audio silence and thus avoid causing jumps in the reference clock time. It's possible that some filters were written to rely on the old behavior, so it's important to check that this change does not cause a problem in any filters you have written. Because some network streaming formats and DVD increasingly allow for periods with no audio, this change was essential.

DVD-ROM Boilerplate Video

The DVD-ROM boilerplate video is provided for developers producing DVD-ROM titles that contain no DVD-Video formatted data. A disc without a proper DVD-Video zone might behave unpredictably when placed in a stand-alone DVD-Video player, possibly ejecting the disc or locking up. You can avoid this confusing situation by placing the DVD-ROM boilerplate video on the disc. When the disc is inserted into a DVD-Video player, it will display a message informing the user that the disc is designed to work in a DVD-ROM PC with Microsoft Windows. The boilerplate files are in the Samples\Multimedia\Media\DVDBoilerplate directory.

New Filters

This version of DirectShow includes the following new filters.

New Samples

This version of DirectShow includes the following new samples.

New Filter-level Interfaces

Seven new filter-level COM interfaces have been added: IAMAnalogVideoDecoder, IAMCameraControl, IAMClockAdjust, IAMFilterMiscFlags, IOverlayNotify2, IAMVideoAccelerator, and IAMVideoAcceleratorNotify.

IAMAnalogVideoDecoder defines the process of video digitization and contains methods for selecting the digitization format, indicating the horizontal lock status, and controlling the time constant on the digitizer phase lock loop (PLL). The IAMCameraControl interface provides local or remote control over a camera. IAMClockAdjust gives timing information to the filter graph from an external source. In the case of multimedia streams, if the application uses both the audio and video streams outside the filter graph, it can communicate clock information to the filter graph using this interface. The filter graph uses the IAMFilterMiscFlags interface to determine which filters are renderers and which are source filters. This is important so that you can determine how many EC_COMPLETE notifications to expect before the movie is done. IOverlayNotify2, which is derived from IOverlayNotify, has been added to include the OnDisplayChange method. IAMVideoAccelerator and IAMVideoAcceleratorNotify have been added to enable a video decoder to access video accelerator functionality during video decoding.

New Graph-level Interfaces

IBasicVideo2, which is derived from the existing IBasicVideo interface, has been added to include the GetPreferredAspectRatio method.

New Class for Controlling Video Crossbars

The CCrossbar class has been added to control video crossbars.

CCrossbar simplifies the WDM Video Capture architecture, providing an alternative to dealing with crossbars through the IAMCrossbar interface. CCrossbar should be used for video capture applications. It works with graphs containing crossbars of arbitrary depth and complexity.

New Application-level Interface

DirectShow has a new application-level COM interface, ICaptureGraphBuilder2. This interface enables you to work with Windows Driver Model (WDM) capture drivers that can capture more than one media type, such as both audio and video.

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