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Media Foundation (MF) is a COM-based multimedia framework pipeline and infrastructure platform for digital media in Windows Vista, Windows 7, Windows 8 and Windows 10. It is the intended replacement for Microsoft DirectShow, Windows Media SDK, DirectX Media Objects (DMOs) and all other so-called "legacy" multimedia APIs such as Audio Compression Manager (ACM) and Video for Windows (VfW). The existing DirectShow technology is intended to be replaced by Media Foundation step-by-step, starting with a few features. For some time there will be a co-existence of Media Foundation and DirectShow. Media Foundation will not be available for previous Windows versions, including Windows XP. The first release, present in Windows Vista, focuses on audio and video playback quality, high-definition content (i.e. HDTV), content protection and a more unified approach for digital data access control for digital rights management (DRM) and its interoperability. It integrates DXVA 2.0 for offloading more of the video processing pipeline to hardware, for better performance. Videos are processed in the colorspace they were encoded in, and are handed off to the hardware, which composes the image in its native colorspace. This prevents intermediate colorspace conversions to improve performance. MF includes a new video renderer, called ''Enhanced Video Renderer'' (EVR), which is the next iteration of VMR 7 and 9. EVR has better support for playback timing and synchronization. It uses the Multimedia Class Scheduler Service (MMCSS), a new service that prioritizes real time multimedia processing, to reserve the resources required for the playback, without any tearing or glitches. The second release included in Windows 7 introduces expanded media format support and DXVA HD for acceleration of HD content if WDDM 1.1 drivers are used.〔(DXVA-HD )〕 ==Architecture== The MF architecture is divided into the ''Control layer'', ''Core Layer'' and the ''Platform layer''. The core layer encapsulates most of the functionality of Media Foundation. It consists of the media foundation pipeline, which has three components: ''Media Source'', ''Media Sink'' and ''Media Foundation Transforms'' (MFT). A media source is an object that acts as the source of multimedia data, either compressed or uncompressed. It can encapsulate various data sources, like a file, or a network server or even a camcorder, with source specific functionality abstracted by a common interface. A source object can use a ''source resolver'' object which creates a media source from an URI, file or bytestream. Support for non-standard protocols can be added by creating a source resolver for them. A source object can also use a ''sequencer'' object to use a sequence of sources (a playlist) or to coalesce multiple sources into single logical source. A media sink is the recipient of processed multimedia data. A media sink can either be a ''renderer sink'', which renders the content on an output device, or an ''archive sink'', which saves the content onto a persistent storage system such as a file. A renderer sink takes uncompressed data as input whereas an archive sink can take either compressed or uncompressed data, depending on the output type. The data from media sources to sinks are acted upon by MFTs; MFTs are certain functions which transform the data into another form. MFTs can include multiplexers and demultiplexers, codecs or DSP effects like reverb. The ''core layer'' uses services like file access and networking and clock synchronization to time the multimedia rendering. These are part of the ''Platform layer'', which provides services necessary for accessing the source and sink byte streams, presentation clocks and an object model that lets the core layer components function asynchronously, and is generally implemented as OS services. Pausing, stopping, fast forward, reverse or time-compression can be achieved by controlling the presentation clock. However, the media pipeline components are not connected; rather they are just presented as discrete components. An application running in the ''Control layer'' has to choose which source types, transforms and sinks are needed for the particular video processing task at hand, and set up the "connections" between the components (a ''topology'') to complete the data flow pipeline. For example, to play back a compressed audio/video file, the pipeline will consist of a file source object, a demultiplexer for the specific file container format to split the audio and video streams, codecs to decompress the audio and video streams, DSP processors for audio and video effects and finally the EVR renderer, in sequence. Or for a video capture application, the camcorder will act as video and audio sources, on which codec MFTs will work to compress the data and feed to a multiplexer that coalesces the streams into a container; and finally a file sink or a network sink will write it to a file or stream over a network. The application also has to co-ordinate the flow of data between the pipeline components. The control layer has to "pull" (request) samples from one pipeline component and pass it onto the next component in order to achieve data flow within the pipeline. This is in contrast to DirectShow's "push" model where a pipeline component pushes data to the next component. Media Foundation allows content protection by hosting the pipeline within a protected execution environment, called the Protected Media Path. The control layer components are required to propagate the data through the pipeline at a rate that the rendering synchronizes with the presentation clock. The rate (or time) of rendering is embedded as a part of the multimedia stream as metadata. The source objects extract the metadata and pass it over. Metadata is of two types: ''coded metadata'', which is information about bit rate and presentation timings, and ''descriptive metadata'', like title and author names. Coded metadata is handed over to the object that controls the pipeline session, and descriptive metadata is exposed for the application to use if it chooses to. Media Foundation provides a ''Media Session'' object that can be used to set up the topologies, and facilitate a data flow, without the application doing it explicitly. It exists in the control layer, and exposes a ''Topology loader'' object. The application specifies the required pipeline topology to the loader, which then creates the necessary connections between the components. The media session object manages the job of synchronizing with the presentation clock. It creates the presentation clock object, and passes a reference to it to the sink. It then uses the timer events from the clock to propagate data along the pipeline. It also changes the state of the clock to handle pause, stop or resume requests from the application. ===Media Foundation Transform=== Media Foundation Transforms (MFTs) represent a generic model for processing media data. They are used in Media Foundation primarily to implement decoders, encoders, mixers and digital signal processors (DSPs) – between ''media sources'' and ''media sinks''. Media Foundation Transforms are an evolution of the transform model first introduced with DirectX Media Objects (DMOs). Their behaviors are more clearly specified. Hybrid DMO/MFT Objects can also be created. Applications can use MFTs inside the Media Foundation pipeline, or use them directly as stand-alone objects. MFTs can be any of the following type: * Audio and video codecs * Audio and video effects * Multiplexers and demultiplexers * Tees * Color-space converters * Sample-rate converters * Video scalers Microsoft recommends developers to write a ''Media Foundation Transform'' instead of a DirectShow filter, for Windows Vista, Windows 7 & Windows 8.〔(Migrating from DirectShow to Media Foundation and comparison of the two )〕 For video editing and video capture, Microsoft recommends using DirectShow as they are not the primary focus of Media Foundation in Windows Vista. Starting with Windows 7, MFTs also support hardware-accelerated video processing, encoding and decoding for AVStream-based media devices.〔(Getting Started with Hardware Codec Support in AVStream )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Media Foundation」の詳細全文を読む スポンサード リンク
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