Windows Media 格式内幕 凌梅
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Windows Media 格式内幕 凌梅






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Windows Media 格式内幕 凌梅 Windows Media 格式内幕 凌梅 Presentation Transcript

  • Windows Media 格式内幕 凌梅 Development Lead Windows Digital Media Division Microsoft Corporation
  • Agenda
    • Opportunities with WM
    • Windows Media Format SDK
  • Windows Media 9 Series Core Promises Unmatched Audio/Video Quality Dramatically Improved Playback Most Comprehensive Platform
    • 20% better compression across the board extends industry lead
    • New voice/screen codecs, video smoothing boost dial-up quality
    • New HD video & 5.1 audio delivers home-theater experiences
    • Fast Streaming provides instant-on/always-on experience
    • Intelligent Streaming optimizes the experience
    • Fast & flexible player with industry’s first Smart Jukebox
    • Industry’s best scalability, reliability & manageability
    • End-to-end extensible architecture
    • Improved economics throughout
  • Windows Media 9 Series Platform Component Drill-down File Codecs DShow DRM Networking DShow DRM License Acquisition Windows Media Server WMS Admin Object WM Server MMC Admin WM Server Web Admin Server Services WM Format SDK Movie Maker Producer Third Party Tools WM Encoder & OCX DRM License Creation Content Discovery/Metadata IIS Networking DRM Codecs File WM Format SDK WMP.DLL Windows Media Player Windows Media Player OCX Authoring On-Line Services Playback
  • WM Codec Parameters
    • Into 3rd generation codecs v8
      • Encoding utility
    • Support streamed / local playback
    • WM is
      • ASF (WMV / WMA)
      • Codecs
      • DRM v1 and v7
    • GOAL
      • Smallest size for quality (e.g. 1/2 MP3)
      • Near DVD @ 500kbps
      • Maintain consistent quality
  • Video Smoothing (Frame Interpolation)
    • Generates missing frames at playback time using optical-flow analysis
    • Improves perceived video quality (motion smoothness) at lower data rates
    • Can be used to improve quality or save bandwidth by encoding fewer frames
      • Bandwidth reduction reduces operating cost for ICPs
      • E.g. MSNBC encodes only 15 frames/sec, but user of WM9 Player will experience full frame rate
  • Video Smoothing demo demo
  • WMV Screen 9
    • Highly efficient compression engine for “palletized video”
      • Typical scenario is capturing application/desktop output for training/demo
      • Entire desktop can be compressed and transmitted at rates as low as 28kbps!
        • Up to 100X more efficient than commonly used Run-length-encoding (RLE)
    • Original Version (V7) shipped in 2000
    • Version 9 improves in both picture quality and CPU usage
      • More efficient handling of continuous-tone images and window dragging/scrolling
  • Screen Codec demo
  • WMA Professional 9
    • New high-performance audio codec to handle greater than CD resolution/channels
      • Up to 96Khz sampling rate, 24-bits, and 8 channels (“7.1”)
        • CD is stereo at 44Khz using 16-bit samples
      • Targets are multi-channel music distribution and movie sound tracks at broadband rates
    • More efficient than existing technologies:
      • Twice as good as Dolby Digital (AC-3) and DTS used in DVDs
      • Blind listening test shows WMA Pro at 768Kbps outperforms all existing codecs in the market
  • WMA 9 Pro Codec demo
    • 192K WMA Pro 5.1 vs. 192K MP3
  • WMA Voice 9
    • Unique “hybrid” voice and music coder for low data rates (<= 20Kbps).
      • First codec to properly handle mixed mode content (e.g. news plus musical commercial)
      • Uses an auto/manual classifier to detect voice/music
      • Applies appropriate coding mode for each segment
    • Voice mode: new proprietary voice codec
      • 20% better than ACELP shipping today (used by Real and WM)
    • Music mode: WMA algorithms
  • WMA 9 Voice Codec demo
    • WMA Voice vs. AMR (3G-GSM)
  • Windows Media Format
    • Our Advantages
      • Extensible file format
        • Support advanced MS and 3rd party codecs
        • Support rich media
      • Scalable
        • Efficient local playback
        • Efficient Streaming (HTTP +)
        • High capacity Media Servers
      • Author once, playback anywhere
        • Streams 28.8Kbps  1Mbps broadband
        • Replay PC’s, PDA’s, Consumer Elec.
          • Car stereos, Cellphones, In home devices, PD’s
  • Windows Media Format File Container
    • Supports files as large as 17 million terabytes
    • Supports multi-bitrate audio, video streams in a file
    • Stores media and metadata in one file
      • Metadata
        • Title, copyright, author, markers, script commands, etc.
        • ID3 v1, v2 music meta-information
      • Media
        • Audio, Video, rich media and Script Commands (URLs, CC)
    Video Stream #n AudioStream Video Stream #1 Script Stream Timeline Rich Stream
  • Windows Media Format File Container (Cont.)
    • Able to select a stream, based on available bandwidth
    • Interleaved data is optimal for HTTP
    • Files can be read sequentially, avoiding expensive seeks
    • Timeline based synchronization
    • Bursty data can be smoothed
      • Send Timestamp (milliseconds)
      • Presentation Timestamp (Rational time units)
    Presentation Time Presentation Time Send Time
  • Rich Feature Set
    • Time-code with Frame accurate seeking support
    • Live DRM
    • Video Smoothing (Frame Interpolation)
    • Rich Media Streaming
    • VBR streaming/progressive down-load optimizations
    • Bandwidth sharing
    • Enables fast stream
    • MBR audio and multiple resolution MBR Video
    • PhotoMotion
  • Photo Motion demo
  • Windows Media Format SDK
    • Win32 only (Win98, WinMe,Win2000, WinXP)
    • COM-style interface
    • Support audio/video/script authoring and playback
    • Enhance metadata authoring and playback
    • DRM support (encryption and decryption)
    • Streaming support (“net-read”, “net-write”)
    • Ideal for applications that handle dataflow
    • Target solutions
      • Jukebox, Live Encoder, Video Editor
    Write Interface Read Interface .wma or .wmv file Raw or Compressed Audio Raw or Compressed Video Script Commands Header MetaData IP Network Raw or Compressed Audio Raw or Compressed Video Script Commands Header MetaData
  • Read with WM Format SDK
    • IWMReader
      • Read WM data.
      • WMCreateReader
    • IWMReaderAdvanced
      • User driven clock
      • Manual stream selection
      • Custom buffer allocation
      • QI from IWMReader
    • IWMSyncReader
      • Synchronous Read
      • No streaming support
      • Ideal for editing app
      • WMCreateSyncReader
  • Encode with WM Format SDK
    • IWMWriter
      • Encode and write WM data
      • WMCreateWriter
    • IWMWriterAdvanced
      • Set output sink(s)
      • Directly write compressed data
      • QI from IWMWriter
    • Output to different destinations
      • Output to file (WMCreateWriterFileSink)
      • Output to port (WMCreateWriterNetworkSink)
      • Output to WM Server (WMCreateWriterPushSink)
      • Custom sink
  • Encode with WM Format SDK (Cont.)
    • Basic calls
        • hr = WMCreateWriter( NULL, &pWriter );
        • hr = pWriter->QueryInterface( IID_IWMWriter, ( VOID ** )&pWriter );
        • hr = pWriter->SetProfile( pProfile );
        • hr = pWriter->SetOutputFilename( outfile );
        • hr = pWriter->BeginWriting( );
        • Hr = pWriter->WriteSample();
        • Hr = pWriter/->EndWriting ();
  • Edit with WM Format SDK
    • IWMMetadataEditor
      • WMCreateEditor
      • Open
      • Close
      • QI for IWMHeaderInfo
    • IWMHeaderInfo
      • Read and edit header attributes
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  • © 2002 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.