ViewCast (VCST)

[pigsheaven]

SHEMP/MELLOWRK: MANY PUNDITS BELIEVE VIDEO ON DEMAND (VOD) WILL REPLACE CABLE. VCST HAS BEEN WORKING WITH MICROSOFT TO PRODUCE VOD. I FORESEE MICROSOFT BUILDING DATA CENTERS LOADED WITH VCST VIDEO STREAMING PRODUCT WHICH WILL DISTRIBUTE CONTENT TO MOBILE DEVICE USERS IPADs and IPHONES WHICH CAN PLAY THE VIDEO ON THEIR FLAT SCREEN DISPLAYS. CHECK THIS OUT!

Summary: Smooth Streaming, Microsoft’s new adaptive streaming technology, is an exciting advancement that brings us closer to Web-based television-like delivery of HD media content. The underlying technology builds on Microsoft® VC-1 codec components to create multiple pre-defined streams, adding mechanisms to automatically adjust the playback to varying consumer connection speeds, and other network playback challenges, enabling higher-quality streaming media delivery over IP and mobile networks. This white paper will introduce you to Smooth Streaming and will explain how you can apply the technology in real-world VOD and live event broadcasting applications.
Whitepaper Smooth Streaming
In this rapidly transforming new media world, conventional broadcasters face continuing challenges in retaining and expanding their viewer base. Digital and hi-definition broadcasting has helped retain viewership by offering better picture quality, but online and mobile video continue to eat away at broadcast and cable audiences as viewers willingly trade quality for the convenience of the “my way, my time” features of the many compelling IP-delivered technologies.
Currently, when it comes to online video, quality may be secondary to convenience for some viewers, but not by much, and for how much longer? Until the day when we all have our own personal, unchallenged gigabit connection to some ultimate media distribution network, development resources will continue to be poured into improving the Internet- and mobile-viewing experience.
Video delivered over private, managed IP networks is already a mature technology and most advancement is in the area of improving compression ratio, that is, picture quality vs. bandwidth. The same advancements are equally important to Internet delivery, but the challenges to successful delivery are much greater when the network is unmanaged. Cramming video down the public Internet is very much like running battleground dispatches through a minefield. You have to do some fairly extraordinary things to reliably get all of the data through to the other side.
Delivering video down less-than-ideal networks is where much of the development is happening today, and one recent example of a deployable advancement is Microsoft’s new Smooth Streaming technology.
Smooth Streaming is one of several fairly recent advancements grouped under the heading of adaptive streaming technology, and its fundamental claim to fame is that it can deliver different streams from the same source
This means you don’t have the 6-10 second or more delay between source and viewer typical of standard streaming technologies. And you don’t get jerky video, as long as the network supports at least the lowest offered rate. In addition, the user enjoys faster start-up and seek times because the player can be directed to the lowest bitrate before moving up to a higher bitrate version.
Another advantage of Smooth Streaming technology comes to light when the player is an older PC with less-than-optimum video rendering components. Decoding the compressed video takes considerable CPU horsepower, more so on the modern highly compressed formats like VC-1 and H.264. High-end graphics cards share the rendering load, but not everyone has these devices in their PCs, and only very recent handheld devices are sufficiently powered to render streams consistently and reliably. In other words, if the player can’t keep up with a higher rate bit stream, the result is no better than if the network itself is the constraint. Smooth Streaming also handles this by doing the same thing it does when the network degrades — it connects to a lower bitrate stream.
The important thing for the content owner to know is that this on-the-fly adjustment happens separately for each individual viewer. That means each attached player makes its own deal with the server (or server farm) that delivers the content. Since the whole delivery is just chunks (packets) of ordinary files delivered by ordinary Web servers, this scales up instantly and massively. Prominent content delivery networks (CDNs), like Akamai and Limelight, have already deployed a huge array of HTTP servers feeding ordinary non-video Web pages, so, other than the need to manage multiple Smooth Streaming component files as a group, they don’t have to do anything too special to handle Smooth Streaming technologies. These massively deployed networks also surface yet another advantage of Smooth Streaming – the inherent HTTP delivery of Smooth Streaming content. These networks place the VOD files out near the edges of the networks, to be closer, and therefore more reliably delivered, to the end users.
This prompts the question of how different, and how many, streams are created in a typical Smooth Streaming title. For a comprehensive answer we’ll need to look a bit deeper into what Smooth Streaming actually does.
material, including HD at 720p or better, with each stream tailored and encoded separately to accommodate varying delivery options, (bitrates, frame sizes, etc.), all with a common timing relationship.
The idea is that the player can be fed sequential chunks of whatever “stream” is most appropriate for the available bandwidth, and as bandwidth increases or decreases, the player can be redirected to the most appropriate stream. The user never sees any of this happening, with the exception that the picture quality changes as the network conditions change.
Although the underlying technologies are quite different, the player experience when viewing a Smooth Streaming title is similar to what Slingbox® viewers are already familiar with: the better the network, the sharper or less pixilated the picture becomes, and the smoother the action becomes on high-motion content.
Note that “stream” is used here in quotes because the actual delivery isn’t really streaming at all: the “streams” are really small sequential chunks of HTTP-delivered progressive downloads. We’ll explain this in more detail a little later.
Savvy readers will immediately wonder how this is different from the long-available multiple bitrate streams of Windows Media® MBR and Real Networks’ SureStream technologies. Some of the difference is in how the “stream” is delivered. MBR content streamed through conventional streaming methods is still transmitted at its encoded rate, which means the network still has to deliver that average rate through the buffering process in order for the client (player) to detect and handle the deteriorating network condition.
The effect isn’t all that helpful – buffering prevents the playback experience from responding to network challenges quickly and the technology doesn’t adjust to the higher bitrates very well once network conditions improve. More importantly, with MBR you still can’t individually configure each stream with options like frame size, etc., so you are still driving less than optimum bit streams down the same path, with no really useful adaptive playback options for the player.
Smooth Streaming, on the other hand, lets you individually tailor the characteristics of each stream that most affect its playability at a given bandwidth. You separately encode the lower bitrate streams in a smaller frame size and the Silverlight™ player will scale it back up to the selected player frame size should it happen to switch to the lower-bitrate stream on-the-fly.
This brings up the concept of buffering and another advantage of Smooth Streaming — minimal wait for stream delivery and the elimination of the “stutter” associated with less than optimal buffering. With conventional streaming, a process called buffering is employed to smooth out the bursty nature of the Internet. If the network connection is faster than the stream playback rate, the buffer fills a bit faster than needed and playback is smooth.
If the net slows down, the player continues, draining the buffer as needed. If the buffer ever empties, playback stops until the buffer has additional data to draw from. If the experience hovers around either side of the “buffer-is” or “very-nearly-empty” point, you get jerky video.
Even when buffering is going well, the buffer is only so big — typically about 5 seconds with Microsoft’s conventional Windows Media. So those of us on great networks still only get no more than about 5 seconds of headroom. That can disappear in, well, 5 seconds when the connection seriously degrades.
Smooth Streaming address this by essentially eliminating the buffer. Instead of buffering up data in the “good times” and drawing from the buffer in the “bad times,” Smooth Streaming simply switches the viewer to whatever “stream” can survive the “bad times” rate.
ViewCast - 2 - Whitepaper - Smooth Streaming
Smooth Streaming - VOD
At the time of this writing Smooth Streaming is deployed as a Video-on-Demand (VOD) technology, although live versions have been field trialed. We’ll discuss what happens in the VOD process first, and then discuss what differences are involved in a live version.
In its VOD form, Smooth Streaming is a collection of individual video and audio files, one set per anticipated playback bitrate, all
processed (encoded) separately and stored on a disk as separate files. These look like any other files and are stored in folders in an entirely conventional manner.
For a given video clip, the following files are created by Microsoft’s Expressions®, the suite of tools Microsoft developed to create Smooth Streaming titles:
• MP4-structured files containing video and (optionally) audio, one file per encoded video bitrate. These files will have an .ISMV suffix.
• One (optional) audio file per bitrate, needed only if the audio isn’t mixed into the video file. These will have an
.ISMA suffix.
• The server manifest file, an XML file that points to and
defines the relationship of all the audio and video files in the title. This is used by the media server and will have an .ISM suffix.
• The client manifest file, an XML which the client uses to
know what “streams” are available, which codecs were used (to select the proper decoder), the encoded bitrates, video
resolutions, captions, etc. This file is sent to the client
immediately upon connection since it offers all needed
instructions on what to play, and how. It will have an .ISMC suffix.
You may note that the audio and video files are each the full length of the clip, not saved as individual chunks. The chunking is done by the server during delivery and is transparent to both the content developer and the viewer.
All of the .ISMV video files have something in common: they share a rather strict set of characteristics that allow the player to freely switch between them at the same point in the video timeline. This is not just a shared-timing relationship (often called ‘temporal alignment’), although that is important and is accomplished by having all streams encoded at the same frame rate. That would be enough if all frames were a complete full frame with all picture elements, but that is not the nature of compression.
There has to be some agreement on where in the various points the server/player can switch between streams, to ensure the switch occurs on a boundary that would deliver a full frame. That involves things like a common closed GOP structure, common entry point headers, etc. That’s all done in the VOD environment by the Expressions encoder and managed by the server/player relationship during playback. To the content owner, the real impact is that you will need to re-encode content to take advantage of Smooth Streaming technology.
How many streams?
Since each set of .ISMV and optional .ISMA files for any given clip title essentially represents one deliverable bitrate, how do you know how many file sets to create?
That depends on your audience. Let’s use an example that allows a full range of playback experiences, from true high-definition (HD) content all the way down to a 400K stream. We’ll make a few assumptions along the way about the bandwidth needed for each, based on Alex Zambelli’s Smooth Streaming online calculator located at http://alexzambelli.com/WMV/MBRCalc.html.
The calculations above reflect a 29.97fps frame rate and a typical 16:9 (1.777:1) aspect ratio, with a minimum bitrate of 400 kbps
and a max of 4.5 megabits. Note that Alex recommends a maximum of 2963 kbps for practical delivery by CDNs, so our example represents a very well-connected user at 4.5 Mbps.
Looking at the table, note that the calculated frame size very nearly maintains the desired aspect ratio of 1.777, but varies by the actual number of pixels in each dimension. As the users’ player and server negotiate the appropriate stream, the frame is adjusted (scaled) by the player to fit in the player’s window, which is typically sized by the Silverlight Web page designer.
In actual practice, assuming SD content, a 700K to 800K stream produces quite acceptable video playback at a typical 640x480, 4:3 display, and is within the range of most DSL users. With a 1.2 Mbps stream for more well-connected viewers thrown in for good measure, you might consider the following set of streams:
Although the Smooth Streaming technology allows you to create multiple streams, it doesn’t make you. The manifest can still be as few as one.
BITRATE WIDTH HEIGHT ASPECT RATIO
4500 1280 720 1.777:1
3185 1024 576 1.777:1
2254 800 448 1.785:1
1595 624 352 1.772:1
1129 512 288 1.777:1
799 400 224 1.785:1
565 320 176 1.818:1
400 256 144 1.777:1
BITRATE RESOLUTION
200 K 320 x 180
300 K 320 x 180
500 K 480 x 240
800 K 480 x 240
1.2 M 640 x 360
ViewCast - 3 - Whitepaper - Smooth Streaming
Requirements for creating and streaming
Smooth Streaming VOD
Now that we have covered what Smooth Streaming is, how do we create and deliver Smooth Streaming media for delivery on demand? There are three main parts:
1. The Encoding environment
2. The Distribution environment - Microsoft IIS Server with Smooth Streaming enhancements, or a CDN equipped with this already.
3. A compatible player -
Let’s explore each separately.
• Content Creation - To create content from existing clips you will
need an encoding environment that creates the new MP4-based
Smooth Streaming file format. Expression Encoder 2 SP1 is the
video encoding mechanism Microsoft offers; it goes along
with their Expression Blend™ 2 Service Pack 1 web development
suite. The full version (but not the trial version) lets you do full
Smooth Streaming VOD content creation using either the VC-1 or the new Microsoft H.264 video and AAC audio codecs.
Specifically, you need SP1 or later so you can select adaptive
streaming video and audio profiles and use the IIS Smooth
Streaming output media format. Expressions Encoder 2 SP 1
publishes the requisite files to the appropriate IIS server, as
detailed below.
• Content Distribution - To serve your own Smooth Streaming content you will need Microsoft’s Internet Information Service
(IIS) 7.0 , running on Server 2008, and will need to install the
Smooth Streaming extension for IIS7. This extension teaches IIS7
how to serve Smooth Streaming media assets to clients.
Reportedly, any server that supports the latest webDAV protocols
is also capable of streaming Smooth Streaming content. If you are
using a hosting provider (CDN), they will need to be similarly
equipped. Akamai has announced high-definition Smooth
Streaming support, announced March 17, 2009, and marketed as AdaptiveEdge Streaming for Microsoft Silverlight.
• Content Viewing - To surface your content, you will need to add Smooth Streaming playback support to your Silverlight application.
There are a number of ways to do this:
> Use any of the Silverlight 2 player templates included with Expression Encoder 2 SP1, to create a suitable Web-based player. Viewers will need only to download the Silverlight player when prompted, assuming it isn’t already present on their PC.
> Use the Open Video Player for Silverlight (http://www. openvideoplayer.com) or,
> Build your own player using Microsoft’s development environment and the MediaStreamSource Class based adaptive streaming implementation.
See http://msdn.microsoft.com/en-us/library/system. windows.media.mediastreamsource(VS.95).aspx
Smooth Streaming - Live
Microsoft very recently released a beta version of Smooth Streaming, that in its final release form supports live ingest. Specifically, it will accept real-time incoming encoded streams (VC-1 or H.264) from devices that can create suitable time-aligned and GOP-controlled streams. IIS Live Smooth Streaming (beta) is an extension for Internet Information Services (IIS) 7.0 that supports live delivery using the same HTTP delivery methods used in VOD deployment.
Live Smooth Streaming (beta) for IIS 7.0 allows you to experiment with live streaming by simulating live delivery as though the content is being ingested from a media encoder. A good encoder engineered for this application and designed to easily integrate into broadcast
workflows is ViewCast’s new Niagara® 7500 HD encoder. It includes a folder of Smooth Streaming video files (files with .ismv file name extensions), and a small encoder applet that creates simulated Live Smooth Streaming output for testing purposes from those .ismv files. You can still create your own Smooth Streaming video (.ismv) files via Microsoft Expression Encoder 2 SP1, just as you would do for VOD applications. In practice, you will use the built-in IIS publishing point manager to create a live publishing point on the IIS Live-equipped server. Once the ingest point is set up, you will push one or more streams to the Live Smooth Streaming publishing point.
Once the publishing point is set up, you can experiment with a live simulation by using the sample encoder to simulate a live ingest. As noted before, this sample application converts any .ISMV file into the needed push format.
Smooth Streaming is certain to be a revolutionary technology for broadcasting HD and professional-grade media over IP and mobile networks. If you’re interested in applying Smooth Streaming to your workflow, the Niagara 7500 HD streaming appliance from ViewCast can offer you a simple solution to take advantage of this advancement in live and video-on-demand broadcast applications.
For more than a decade ViewCast has offered the highest degree of reliable, professional-grade streaming products engineered to simplify the complex workflows required in the management and delivery of media to computers and mobile devices. Find your ideal solution for expanding your audience through the multi-platform world of Webcasting, IPTV, VOD, mobile TV, and digital asset management by talking with one of our streaming specialists today, or simply visit http://www.viewcast.com.
3701 W. Plano Parkway
Suite 300
Plano, TX 75075
USA | 800.540.4119
Europe, Middle East, Africa | + 44 1256 345610
©2009 ViewCast Corporation. All rights reserved. Osprey®, Niagara®, SimulStream® and
Niagara SCX® (and design)™ are registered
trademarks of ViewCast Corporation.
Next Generation Streaming Media Solutions
ViewCast Niagara® 7500 HD encoder