1 / 68

Media Processing Workflow

Media Processing Workflow. Alex Zambelli Media Technology Evangelist Developer & Platform Evangelism alexzam@microsoft.com. Workshop Overview. Silverlight media capabilities Smooth Streaming 101 15 min break Live Smooth Streaming Workflow and architecture 15 min break

cain
Télécharger la présentation

Media Processing Workflow

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Media Processing Workflow Alex Zambelli Media Technology Evangelist Developer & Platform Evangelism alexzam@microsoft.com

  2. Workshop Overview • Silverlight media capabilities • Smooth Streaming 101 • 15 min break • Live Smooth Streaming • Workflow and architecture • 15 min break • Encoding for Smooth Streaming

  3. A Brave New World • Encoding 320x240 video on a laptop is “so 2002” • HTTP adaptive streaming has entirely changed the game in the past 2 years • The future for Silverlight is all Smooth Streaming, all HD • Video quality is better than ever, but at the price of complexity and bandwidth • Don’t worry, it only gets easier from here

  4. Silverlight Media Formats • Windows Media • ASF file format (*.asf, *.wmv, *.wma) • VC-1 (WMV9), WMV8, WMV7 video codecs • WMA Pro, WMA Standard, MP3 audio codecs • MPEG-4 • MP4 file format (*.mp4, *.3gp, *.mov) • H.264 video codec (Baseline, Main, High profiles) • AAC audio codec (AAC-LC profile)

  5. Silverlight Media Extensibility • Smooth Streaming • VC-1 and H.264 video • WMA Pro, WMA Standard and AAC-LC audio • Supported via Smooth Streaming Media Element extension • MediaStreamSource lets developers add support for 3rd party codecs, formats and delivery methods

  6. Silverlight Media Protection • Silverlight DRM, powered by PlayReady • PlayReady AES-256 encryption • Windows Media DRM encryption • Silverlight 3 • VC-1 and WMA encryption only • Live DRM (Direct License Acquisition) only • Silverlight 4 • H.264 and AAC encryption • Offline DRM

  7. Silverlight Media Delivery • Windows Media Services streaming • Windows Server 2008 and 2003 • Unicast (WMS HTTP) • Multicast • HTTP progressive download • Any HTTP 1.0/1.1 web server • IIS Smooth Streaming • Windows Server 2008 (IIS7)

  8. Silverlight Media Framework • No need to reinvent the wheel every time a Silverlight video player is needed • Silverlight Media Framework:http://smf.codeplex.com • All essential playback features plus advanced Smooth Streaming features • DVR, Fast Forward, Rewind, Replay, Slow Motion • Markers, captions, dynamic ad insertion • Rich analytics and logging

  9. Media Delivery Methods • Unicast • Traditional Streaming • Progressive Download • HTTP-based Adaptive Streaming • Multicast • IP Multicast

  10. Unicast Many one-to-one streams Requires more bandwidth per user May require more servers For private and public networks Origin Server

  11. Multicast A single one-to-many stream Uses bandwidth of only one stream Requires multicast-enabled networks Typically requires fewer servers Origin Server

  12. Unicast Methods Movie HTTP Adaptive Streaming Video @ 01:04? Video @ 01:06? Video @ 01:08? Traditional Streaming Play Seek Pause Progressive Download Movie

  13. Internet Streaming Challenge • Traditional streaming designed for efficient media delivery • Works well in small networks but on the Internet suffers from serious drawbacks: • Doesn’t scale to today’s Internet audience • Doesn’t take into account today’s Internet structure and organization • Designed for network conditions less volatile than Internet traffic

  14. HTTP Adaptive Streaming • Hybrid media delivery method • Acts like streaming but is in fact a series of short progressive downloads • Video and audio delivered as series of small files over HTTP • Built for the Web • Leverages existing HTTP caches • Scales exceptionally well to meet high demand • Resilient to network unpredictability • Client can seamlessly switch video quality and bit rate based on perceived network bandwidth and CPU resources • Applicable to both on-demand and live delivery

  15. Windows Server Media Delivery IIS Media Services • Traditional Streaming • Unicast • WMS RTSP • WMS HTTP • Multicast • WMS Multicast • Progressive Download • Bit Rate Throttling • HTTP Adaptive Streaming • Smooth Streaming

  16. Smooth Streaming • Smooth Streaming • Microsoft implementation of HTTP-based adaptive streaming • Best of both worlds • Responsive and efficient like streaming • Cheap and scalable like progressive download • Superior user experience • No buffering, no stutter • Instant start, instant seek • Seamless bit rate switching based on bandwidth and CPU

  17. Multi Bit Rate Revisited 00:27.24 03:47.16 05:05.04 07:33.10 2.4 Mbps 1.5 Mbps 700 kbps 300 kbps

  18. Adapting Bit Rate in Real-Time 300K @ 00:00? 700K @ 00:02? 2.4M @ 00:04? 1.5M @ 00:06? 2.4M @ 00:08? 300K (start quickly) 00:00 00:02 00:04 00:06 00:08 700K (good network) 2.4M (great network) 2.4M 1.5M (glitch) 2.4M (play on…) … Bit Rate Heuristics 300K

  19. Smooth Streaming Design • Smooth Streaming File Format based on MP4 (ISO Base Media File Format) • Video is encoded and stored on disk as one contiguous MP4 file • One file per bit rate • Each video Group of Pictures (GOP) is stored in a separate Movie Fragment box • This allows accurate fragmentation at key frames • Contiguous file is virtually split up into chunks when responding to a client request

  20. Smooth Streaming File Format File Type (ftyp)

  21. On-Demand Presentations • MP4 files containing video/audio/data fragments • New file extensions instead of *.mp4 • *.ismvfor files containing video and audio tracks, or only video tracks • *.ismafor files containing only audio tracks • On-demand server manifest file • File extension: *.ism • Describes the relationships between media tracks, bitrates and files on disk • Uses SMIL 2.0 XML format • Client manifest file • File extension: *.ismc • Describes available streams, codecs, bitrates, resolutions, metadata • Uses XML format

  22. On Demand Server Manifest

  23. On Demand Client Manifest

  24. Client-Server Communication • All requests to the server are formed as RESTful URLs • Client always first requests the client manifest:http://iis.net/video.ism/Manifest • After parsing the manifest the client begins making requests for fragments by indicating bit rates and offset times it learned from the manifest:http://iis.net/video.ism/QualityLevels(350000)/Fragments(video=40040000)http://iis.net/video.ism/QualityLevels(48000)/Fragments(audio=62293333) • Every valid HTTP request returns a file of MIME type “video/mp4”

  25. Serving Fragments On Demand • IIS7 Smooth Streaming handler interprets the RESTful URL request • It maps the quality level to a physical ISMV file based on the server manifest (*.ism) and calculates the fragment location within the contiguous ISMV file based on the time offset • Because the wire format (fragment) is just a subset of the disk format (MP4), the extraction process is simple • No re-muxing necessary • Dynamic stream switching logic is fully implemented in Silverlight application code – no server-side detection

  26. Demo • DEMO: • Setting up On Demand publishing points • Using Fiddler to monitor Smooth Streaming traffic

  27. Live Smooth Streaming • Live publishing point identified by *.isml extension • Client-server communication very similar to on-demand • Server continually appends MP4 file with new fragments from encoder and makes them available to client • This allows DVR-like seeking within the existing archive

  28. Encoder-Server Communication • Encoder pushes fragmented MP4 stream to server in body of a long-running HTTP POST requesthttp://iis.net/live.isml/stream(720p) • Encoder inserts Live Server Manifest Box into start of MP4 stream • Contains a SMIL-formatted Live Server Manifest very similar to On-Demand Manifest • Describes all tracks in that encoder’s stream

  29. Encoder-Server Communication • Each sent fragment contains a box with absolute time and duration • Timestamps are typically derived from the input source Linear Time Code (LTC) • If multiple encoders are used to encode the same video source, it’s essential that a time code generator is used to keep their LTC in sync

  30. Serving Live Fragments • Server parses the encoder manifests and starts collecting MP4 fragments • Server builds a cumulative runtime index in memory for all incoming fragments • Server stores fragments into a temporary DVR ISMV or a permanent ISMV archive • When the pub point is shut down, server generates ‘mfra’ index box for ISMV archive

  31. Live Client Workflow • Client requests the latest manifesthttp://iis.net/live.isml/Manifest • Server adds up all the encoder manifests and the runtime fragment index and sends the latest version to the client • Every fragment contains information about the next fragment • No need to repeatedly download manifest • Client builds its own cumulative runtime index based on the lookahead info in the fragments

  32. Demo • DEMO: • Basic Live Smooth Streaming workflow

  33. Live Smooth Publishing Points • ISML files are SMIL 2.0 formatted XML configuration files • Live publishing points can be created via the IIS Manager UI or by manually creating ISML files on server • Both push and pull publishing models are supported • Live publishing points can also push to and pull from other live publishing points

  34. Live Publishing Point – IIS Mgr

  35. Live Publishing Point - ISML

  36. ISML Syntax • sourceType • Push: source streams will be pushed to pub point • Pull: pub point will pull streams from listed URLs • publishing • Streams: pub point can serve streams to other live pub points • Fragments: clients can request fragments • Archives: archiving is enabled • lookaheadChunks: number of fragments server will buffer before making them available to clients • manifestWindowLength: length of DVR moving window • archivePath: local path where archives will be written

  37. Ingests and Origins Origin Server: Delayed Stream Origin Server: Delayed Stream Encoder Ingest Server Origin Server: Realtime Stream Origin Server: Realtime Stream 8 Mbps Origin Server: VOD Archive Origin Server: VOD Archive

  38. DEMO • DEMO: • Advanced Live Smooth Streaming workflow

  39. Network Design Considerations • Bandwidth, bandwidth, bandwidth Encoder egress bit rate = (All video and audio bit rates together) x (Number of ingest publishing points) • Leave enough headroom for bit rate spikes and bursts • Play it: leave 50%-100% headroom

  40. Building Smooth Streaming Origins • Network • Make sure NICs can handle the cumulative ingress and egress bandwidth • CPU and memory • Follow typical server configuration guidelines • Disk • Live Smooth Streaming can require high read/write rates • 10,000 RPM disks are a good idea

  41. Redundancy and Failover • Encoders • Active-active redundant encoder configuration not supported • Encoder hot swap is possible as long as encoder doesn’t signal end-of-stream to server • Configurable time-out periods can help survive temporary loss of network connectivity • Some encoders support pushing to multiple publishing points concurrently, while others do pub point roll over in case of failure

  42. Redundancy and Failover • Servers • IIS is designed to discard duplicate fragments • This allows ingest and origin servers to be set in active-active configuration Ingest server: Primary Encoder Origin server Ingest server: Secondary

  43. Redundancy and Failover • Origins • CDNs can dynamically change DNS to redirect traffic to secondary origin when primary fails Ingest server: Primary Origin server: Primary DNS Encoder Ingest server: Secondary Origin server: Secondary

  44. Video Encoding

  45. Smooth Streaming Encoders • Many vendors to choose from: • Anystream (Grab Networks) • Digital Rapids • Envivio • Inlet Technologies • Microsoft • Rhozet (Harmonic) • Telestream • VBrick • ViewCast • Winnov

  46. H.264 or VC-1? • Customers should choose whichever codec best fits their encoding workflow and meets their quality requirements • However, keep in mind: • H.264 decoding is typically more CPU intensive than VC-1 decoding for the same resolution and frame rate • In Silverlight 3: H.264 decoding requires about 15-25% more CPU time than VC-1 decoding with similar content properties • Good rule of thumb (for now): • For HD video, use VC-1 to reach largest audience • For SD video and smaller, use H.264 if quality gains are noticeable

  47. Encoding for Smooth Streaming • Use VC-1 Advanced Profile or H.264 Main/High Profile • 2 second key frame distance works very well • Must be closed GOP • Client heuristics work best with fixed length (non-adaptive) GOP • Set video buffer size to 2x-3x key frame distance • Use WMA Professional audio codec for best quality at low bitrates • Comparable to HE-AAC – excellent stereo quality even at 48 kbps • Client heuristics are currently tuned for CBR content, so if using VBR set the peak bit rate within 15% of average bit rate for best playback

  48. Multi Bit Rate Encoding Revisited 00:27.24 03:47.16 05:05.04 07:33.10 2.5 Mbps 1.5 Mbps 750 kbps 350 kbps

  49. Variable Resolution • Why do we vary encoded resolution together with bit rate? • Encoding the same resolution at inappropriately low bit rates introduces objectionable compression side effects into the video: blockiness, twirling details, color smearing, etc. • By lowering the resolution proportionally to the bit rate we maintain a consistent level of compression quality in exchange for giving up some visual detail • It’s a compromise: between two evils, customers prefer a blurry picture over a blocky picture

  50. VC-1: 640x360 at 1250 kbps

More Related