Digital Video Resources

Video Conferencing Cookbook Video conferencing in its most basic form is the transmission of image (video) and speech (audio) back and forth between two or more physically separate locations.

Digital Video for the Millenium an overview of digital video on demand -- the underlying technology, the client/server capabilities currently available and development areas for the near future. (PDF Version)

Apple G4 Technical Specifications

Digital Video Primer (

Networked Digital Video with guest experts Joel Mambretti amd Bob Taylor? Is digital video on campus "just around the corner" or is it already here? Why do we need, do we need, high-res video? Can the commodity network handle short term video demands?

[Joel Mambretti is the Director of the International Center for Advanced Internet Research at Northwestern University, in Chicago. He chairs the Internet2 Digital Video Initiative and the Digital Video Working Group for the Coordinating Committee for International Research Networks. He recently co-authored, with Andrew Schmidt, a book published by Wiley entitled, the Next Generation Internet.

Bob Taylor, also at Northwestern, is Director of Academic Technologies. Bob's role is to support Northwestern faculty in the implementation and adaptation of technology towards instructional and research goals, providing training and one-on-one consulting to faculty members and managing the University's electronic classrooms and computer lab/classroom facilities.]

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Digital Video: the representation or encoding of an analog signal in digital bits for storage transmission and display. The Southeastern University research Association (SURA) awarded ViDe, a five institution consortium, a grant for developing a number of valuable resources. White papers on Digital Video are the result of several conferences and workshops in this area. The Video Conferencing Cookbook (http://sunsite.utk.edu/video_cookbook/) was released in February, 1999. The white paper Digital Video for the Next Millenium (http://sunsite.utk.edu/video/) provides an overview of digital video on demand, the texhnology, and the client server capabilities. is a growing presence on today's campus.

global perspective: everyone understands immediately about having high quality video over the network ...although "high quality" needs to be clarified, and raises issues of access...

network perspective: primarily used within the campus which is in the best position to offer high quality digital video...campuses are THE testbed for high-quality streaming video...Internet II envisions a larger environment for exchange.. but campuses need to plan on upgrading the campus infrastructure.

Once faculty see MPEG1 they will want to use dv as a way to enhance learning - and the campus will need to think about bandwidth, streaming requirements, and the like Northwestern began using high quality networked video in 1998 - MPEG1 quality video = CDRom video or older VHS video (325 x 240 @ 30 fps for spanish instruction (spanish soap opera). 28 minute episodes distributed to other campuses - quarter screen in natural resolution, with very good audio. Faculty were interested...and the challenges of distribution began. (eg. last minute peak demand by students)

MPEG1:

The first digital video and audio encoding standard, MPEG-1, was adopted as an international standard in 1992 to provide digital video at bit rates up to 1.5 Mb/sec.* The impetus for the standard was to provide encoding and playback of VHS-quality digital video for CD-ROM playback.

The standard implementation for MPEG-1 (known as “constrained bit stream”) supports 352 pixels x 240 lines/sec at 30 frames/sec and requires 1.5 Mbps bandwidth for transport. MPEG-1 compression relies on the considerable redundancy of information within and between frames to compress a video object without significantly compromising the integrity of the information it contains.

This format is the standard of greatest interest as todays campus "ubiquitous" streaming DV solution - requiring no additional hardware to see full motion, full color, good audio on any 1999 vintage computer. Our campus uses 10 mbps switched ethernet, and we can deliver adequate quality 1.5 mbps MPEG1 streams to any campus computer. (A 30 minute streaming presentation is 30 times 60 time 1.5 mbps or approx. 3 GB) Northwester just switched from shared to switched ethernet at the request of faculty for instruction purposes...30 minutes of dv is approximately ... The advantage to MPEG1 is it can deliver full screen, full motion, full audio can be decoded by any PC/Mac with javascript client.

MPEG2:
MPEG-2, published as a standard in 1994, is a high-bandwidth encoding standard, supporting a bandwidth range of approximately 2Mbps to more than 20 Mbps. It was originally designed for coding of television broadcast video with CCIR Rec. 601 resolution at data rates below 10 Mbps, but was expanded to encompass HDTV requirements at app. 12-20 Mbps.

MPEG-2 was designed to encompass, and be backward compatible with, MPEG-1 encoding techniques but was also enhanced to support interlaced video, as provided by television input sources. The MPEG-2 standard was designed for scalability and flexibility, supporting many levels of service depending on the needs of the application. It was expected that an MPEG-3 standard would be developed for HDTV (high definition television), but the MPEG-2 standard scaled to encompass the bandwidth requirements of HDTV.

The most common MPEG-2 compression is main level (“CCIR 601”) at 720 pixels x 480 lines, 30 frames/second. The sweet points for MPEG-2 support the bandwidth bit rates of 2-6 Mbps, scaling up to 40 Mbps for very high-level HDTV applications.

The MPEG-2 encoding standard builds on, and is backward compatible with, the statistical redundancy compression of MPEG-1. The most important difference between MPEG-1 and MPEG-2 is the encoding of interlaced frames for broadcast TV. MPEG-1 supports only progressive frame encoding, while MPEG-2 provides both progressive frame and interlaced frame encoding. Video movies, originally in a film format, are a progressive frame format.

(quality of current dvd-roms; 18" direct satelite tv; Larger screen, faster refresh rate, bandwidth of 3-10 mbps.
This standard exceeds the limits of our network - "switched 10 mbps ethernet " and the standard MAC / PC computers require a special decoder card. So MPEG2 is not ubiquitous - since can't be decoded without codec cards.... Later 2000 we'll see ultra-bright MAC and PC clients that can handle MPEG2 video decoding - and the switched 10 mbps can handle this quality only at the lower end.

Television broadcasts are an interlaced format. A broadcast frame is created with two separate fields, a top and bottom interlaced field, with the first line of the bottom field appearing immediately after the first line of the top field. MPEG-2 splits frames into two fields for interlacing, so that 30 frames/sec becomes 60 fields/sec.

MPEG-1 and MPEG-2 were developed for reliable moderate to high-bandwidth transport. Neither standard successfully supports streaming over the Internet, particularly at the common modem speeds of 28.8 to 56 Kbps available for personal Internet use. Encoding formats proprietary either to a microcomputer platform or a specific manufacturer arose to provide streaming digital video to Internet users at low-bandwidth ranges. MPEG-4 is expected, over time, to displace many proprietary formats but at present, proprietary "de facto" standards are well-established on the Internet. QuickTime began as a Mac-based video encoding, file management and playback system but with version 3.0 became a cross-platform encoding format, supporting digital video on Mac and Windows. QuickTime video files have the file extension .mov. QuickTime is a versatile digital video encoding format, supported by a range of commercial and shareware software products, including encoding, editing, and client plug-ins. QuickTime 4.0, released in April, 1999, supports timecode tracks and Web transport and streaming protocols, including HTTP, RTP and RTSP. QuickTime 4.0 provides built-in support for digital video, including MiniDV, DVCPro, and DVCam camcorder. The QuickTime digital video file format was selected as the basis for MPEG-4. Although the multi-track, object-based MPEG-4 goes beyond QuickTime functionality, the QuickTime wrapper will be supported by MPEG-4-based service and streaming, making this a safe interim choice for low-bandwidth videos over Internet. Microsoft ActiveMovie (AKA Video for Windows), provides digital video technology, including encoding, file naming and playback, on a Windows platform. The file format is identified by the .avi (audio & video interleave) extension. Video and multimedia creation and editing packages for use on Windows platforms, such as Adobe Premiere must support the .avi file format Microsoft ASF (Advanced Streaming Format) is an open streaming format developed collaboratively by Microsoft, Progressive Networks, Inc., Intel Corp., AdobeSystems Inc. and Vivo Software Inc., as well as from the feedback and suggestions of other companies. It is currently available in beta in version 1.0 for use with Microsoft's NetShow streaming media client/server software and in version 2.0 as a preliminary developers' toolkit. The ASF format is intended for streaming synchronized audio, video and multimedia for use over the Internet. Progressive Networks’ RealVideo (file format extension .rm or .ram) is a robust low-bandwidth format intended for Internet streaming. RealVideo is supported by a range of commercial and shareware products including encoding software, multimedia authoring tools, server software and client plug-ins. The G2 Real Media client supports SMIL synchronized text files, audio only, and plug-in extensions for MPEG. RealVideo is in widespread use and is supported by a complete client/server suite, including publishing, synchronized multimedia, and streaming server software, available in shareware and inexpensive commercial versions. Other encoding formats proprietary to different manufacturers include Intel’s Indeo format and Cinepak, first developed by SuperMac Technologies and now owned by Radius. M-JPEG is a quasi-standard provided by many video encoding cards. M-JPEG consists of sequential JPEG-encoded frames. JPEG stands for Joint Photographic Experts' Group and is the popular name for the still image encoding standard JFIF (JPEG File Interchange Format). JPEG is an intraframe compression standard intended for still images only. Video encoding cards provide M-JPEG compression so that the resulting digital video file may be edited. MPEG-1 and MPEG-2 files include I-frames, which are compressed intraframe, but also P-frames and B-frames, which do not include essential information, such as color or movement, but instead reference that information in a forward or backward frame. Since frame types are not eye-readable, video editing can result in the removal of critical reference frames. Some video cards now provide editable MPEG-1, eliminating the need for M-JPEG encoding. Editable MPEG-2 was introduced by Hewlett-Packard in 1997 for its HP MediaStream broadcast server.

MPEG-4, the latest encoding standard from MPEG, was finalized in October 1998 and should be ratified as a standard in the first half of 1999. MPEG-4 arose from a need to have a scalable standard supporting a wide bandwidth range from streaming video at <64 Kbps, suitable for Internet applications, to app. 4 Mbps for higher-bandwidth video needs. MPEG-4 also arose from a desire, as digital encoding matures, to advance beyond simple conversion and compression to object recognition and encoding, as well as the provision of synchronized text and metadata tracks, to create a digital file that carries a meaning greater than the sum of its individual parts.

MPEG-4 supports both progressive and interlaced video encoding. The standard is object-based, coding multiple video object planes into images of arbitrary shape. Successive video object planes (VOPs) belonging to the same object in the same scene are encoded as video objects. MPEG-4 supports both natural (“analog”) and synthetic (“computer-generated”) data coding. Some VRML technology is incorporated to encode dimensionality.

MPEG-4 compression provides temporal scalability utilizing object recognition, providing higher compression for background objects, such as trees and scenery, and lower compression for foreground objects, such as an actor or speaker—much as the human eye filters information by focusing on the most significant object in view, such as the other party in a conversation. Object encoding provides great potential for object or visual recognition indexing, based on discrete objects within a frame rather than requiring a separate text-based or storyboard indexing database. In addition, MPEG-4 provides a synchronized text tract for courseware development and a synchronized metadata track for indexing and access at the frame level.

Originally used for very low quality video-phone applications, and now applied to video applications that anticipates the entirely digital creation and repurposing of video. Not passive video streams but more interactive, modular objects, graphics, live video, stored video, video can respond to clients… now optimized for low - med - high quality video.)
MPEG4 bandwidth is focused on low to moderate bandwidth - 56 kbps- 500 kbps more interactive applications. Quicktime 4 file format has been adopted as the standard file format for mpeg4, but it isn't clear whether quicktime streams will be synonymous with mpeg4.

FAQ's

Things encoded in mpeg1 on today's campuses - wont be obsolete anytie soon. mpeg2 will see use primarily in dedicated distance ed environments, special equipment, limited audience (medical imaging)

Everyone today has to have 10 clients to read 10 diff proprietary video formats which is insupportable ... There is a need for one video client and open standards, e.g. in web-based video today there are too many proprietary standards...we need people to start including mpeg 1, 2 standards included in their products along with their proprietary standards... Web based video products still use a number of proprietary formats...

Northwestern Advanced Media Creation Studio work on Imac DV and G4 video solutions, and Avid DV Express $10K does 30 fps DV editing.

Best format for web-based streaming for modem users (lower bandwidth web based video streams - 1-5 fps - pays attention to maintaining the audio stream at the expense of the video quality. (Quicktime, Real streaming , Sorenson broadcaster,...)

broadcasting - resource is treated a rationed scarce resource...lowest common denominator. (eg. NASA TV, Challenger Launch)

narrow casting - specialized programming for custom audiences. ..the promise of the Internet.

Unicasting - one to one streaming connection - "video on demand". the resource is one entire stream, carried over the network to serve one individual..multiple streams gets very expensive in this mode.

Multicasting - many people able to take advantage of one scheduled video stream, conserves bandwidth, requires scheduling on the part of clients..spanish instruction at Northwestern , etc. could be scheduled for multicasting.

Which proprietary low-bandwidth formats are best? This is mostly an application-specific decision. In the author's opinion, RealVideo and Audio are widely available, generously supported with very good free clients, free encoders, free plug-in applications, free server software (20 streams at date of writing), etc. File quality and streaming are excellent, as is support for the SMIL (synchronized multimedia integration language) standard for incorporating digitized text for audio file transcripts and distance learning. Other new features include RealFlash, RealMedia's integration of Macromedia Flash into its authoring product. The RealSystem seems determined to maintain its enormous presence on the web. If plug-in integration for streaming MPEG-4 is offered, and the current bandwidth streaming limitation of 900KB overcome, RealMedia will remain an excellent low-bandwidth solution.

QuickTime's file format provides the wrapper for MPEG-4. The file format is excellent for download and play, but until recently, streaming capability was lacking. QuickTime 4.0, which was released in April 1999, incorporates streaming functionality and protocol support. In addition, QuickTime 4.0 provides built-in support for digital video, including MiniDV, DVCPro, and DVCam camcorder. QuickTime 4.0 will include source code, allowing great flexibility for custom APIs. The compatibility with MPEG4, while not at the object recognition and manipulation level, is a real plus.

Video Conferencing - important to researchers, distance education, an important modality. Cureent work on H323 for video conferencing over the internet...technical challenges remain to be resolved. We need to develope an addressing system...similar to a phone number.

Startup...on our campus today.

1. Encoding or Digitizing the Video

   Incl. copyright considerations in your planning, DV camcorder, digital camera, firewire (IEEE1394, Firewire, Ilink)

   With older analog video resources, an encoder card is needed that accepts an analog signal through a cable into an interface card and feeds the signal into the encoding hardware and software to encode the video into digital form. Today, there are devices such as sume digital cameras, and boxes that convert analog video to digital.

   A video-encoding card accepts analog inputs from a VCR or a video camera and converts the analog format into a digital video file. Encoding hardware and software vary greatly in cost and therefore support a wide range of functionalities, including, as the cost increases, higher quality output, separate input for video and audio, faster encoding, multiple file and batch file processing, analog output (e.g. digital video back to analog videotape), uncompressed conversion and, at the present time, a range of encoding formats, including M-JPEG, MPEG-1, editable MPEG, MPEG-2, Video for Windows/ActiveMovie, and QuickTime.
   
   In the past few years, digital video cameras have become available, in commercial and consumer-quality models. A high performance serial bus, IEEE P1394, popularly known as FireWire, was developed by Apple Computer but now supported by many vendors to support data transfer rates of 100, 200 or 400 Mbps. These high transfer rates mean that digital video can be transported directly from the digital source (camera, DVD, etc.) into the microcomputer with no processing delays. FireWire streams video data off a hard drive in real time without computer assistance.
   
   FireWire transfer speeds, currently at 100-400 Mbps, will increase to 800 Mbps/multi-Gbps in the next release--1394B. The high transport speeds can result in latency problems, requiring significant buffering capacity, as can a heavily-loaded PCI bus, but these problems will abate as FireWire integration becomes the norm, and microcomputers are designed for FireWire integration.
   
   One issue with digital video camera content creation is that the resulting digital video files are generally in formats not currently supported by digital video client/server systems. When investigating digital video cameras, insure that a method exists to output the file to a standard format (AVI-to-MPEG or directly to MPEG)--whether through an editing program such as Adobe Premiere or a transcoding system such as Heuris.

2. editing tools : Avid Express ($10K), Final Cut Pro 1.2, IMovie, Premier
   
   
3. Distributing Digital Video (DV) to the Desktop:Once a video is created, it is stored and then transported to the desktop for playback. Digital video created on a computer can be stored on the computer, opened and played back, just as a document is opened in a word processing program for reading, editing and printing. A server must generally be employed to store and share a video over a network--whether a campus or building LAN or the Internet. Digital service includes real time broadcast, non-streamed downloading or streaming to the desktop. Video service may be multicast (“one to many”) where one video stream is served to many viewing clients or unicast (“one to one”) where one video stream is served to one viewing client. Real time broadcasting converts analog video to digital on the fly.
   
   Analog video is received by the video server directly from a broadcast feed or a video camera, encoded in real time, and then served as a multicast video stream to many clients. Real time broadcasting also includes the real time delivery of files already in a digital format, such as a digital camera or satellite transmission.
   
   Digital video can be received at the desktop for playback in two ways: non-streaming or streaming video. Non-streaming video requires that an entire video file be downloaded and lacks the timing functionality for smooth packet streaming. A video server is not required to store and serve non-streaming digital video.
   
   Video streamed via the Web must be transported within the IP architecture. Streamed video has low tolerance for the enforced reliability of TCP, which would keep an application waiting for the retransmission of dropped packets. UDP (User Datagram Protocol) is frequently used in place of TCP as a transport protocol for real time applications, such as digital video.
   
   UDP uses the Internet Protocol (IP) to transport a data unit ("datagram"). UDP supports digital video because it does not divide the data stream into packets for reassembly at the client end. However, UDP also does not order the datagrams into the correct sequence. Applications using UDP must insure, at the receiving end, that the complete message has arrived, in the correct sequence order.
   
   RTP (Real-time Transport Protocol) is a UDP protocol that provides payload type identification, sequence numbering and time stamping. RTP allows for packets to be transported out of order and reassembled in correct order at the receiving end. Digital video has low tolerance for disordered packets and dropped frames. It is used on the MBONE, for interactive audio and video, particularly conferencing sessions. RTP is used with a companion protocol, RTCP (Real-time Control Protocol), which provides periodic control packets to an application to monitor the quality of the data distribution.
   
   RTSP (Real-time Streaming Protocol) is an application-level rather than a simple protocol, since it works with many transport protocols--TCP, UDP, RTP, and IP Multicast. RTSP was designed to support streaming multimedia in unicast and multicast applications. It provides increased functionality at the client end for playback, seeking, etc. and has been described as a "video remote control" for the computer. Among other features, RTSP allows for interoperability between server and client implementations from different vendors. RTSP can be used with RSVP to establish and manage reserved-bandwidth streaming sessions. Progressive Networks' Real Player G2 is an example of an RTSP client.
   
   RSVP (Resource Reservation Protocol) provides Quality of Service (QoS) by allowing an application invoking RSVP to reserve end-to-end bandwidth, memory and CPU resources sufficient for the demands of the application. RSVP requires that all network components work together to provide guaranteed resources for the application, so all components--hosts, routers, hubs, etc.--must support RSVP. Although RSVP is a fairly mature standard, it is not heavily implemented, due at least in part to the requirement that all network components support the protocol.
   
   IP Multicast supports one-to-many service for a data stream. All routers in the network infrastructure must be IP multicast-enabled. Some multicast applications, such as Progressive Networks' RealSystem G2, are able to bridge non-multicast-enabled network segments. A process asks its host for permission to join or leave a group. IP multicast-enabled routers query their groups to identify the processes currently belonging to each group. On the Internet, IP Multicast is implemented on the MBONE and, increasingly, by service providers who will multicast your video to your authenticated users for a fee. Multicast is supported natively on advanced networks, such as vBNS and Abilene.
   
   Quality of Service (QoS) provides a mechanism whereby a client can request priority access, sufficient bandwidth and other network service characteristics to guarantee acceptable application performance. QoS sounds deceptively simple but is difficult to implement since the QoS protocol (such as RSVP) must be enabled on all network devices to insure that the bandwidth allocation is supported across the network. QoS becomes increasingly important as more clients request unicast video applications or participate in a multicast transmission. Most networks currently utilize admission control (users beyond a prescribed stream limit are denied service until a stream is freed) or "best effort," where all users share bandwidth equally and suffer equally, as bandwidth utilization approaches capacity.
   
   
4. distribution (video servers - IBM Video Charger, Sorenson Broadcaster, Quicktime Streaming, Real Video Server ) Delivery format (multicasting from a streaming server conserves bandwidth, unicasting - video on demand - easily consumes available bandwidth)
   
   
5. Playback on the Desktop:
   
   When a streamed video file is received at the desktop, the file type must be recognized, through information provided in the header, and then opened. The file must be cached until sufficient data is received to allow for smooth, continuous playback. Playback includes controls such as forward, reverse, stop and play, as well as freeze-frame, content bookmarking, audio volume control and sizing of the viewing window. Client software, frequently a web-browser plug-in or browser helper-application, provides this functionality. If you visit a web site with audio or video, you are usually alerted to the plug-in viewer needed and provided a link for free download of the plug-in. RealVideo, Windows ActiveMovie (AKA NetShow), and QuickTime are common file formats with freely-available viewers.
   
   In the past, different client players were required for different file types. Currently, many standard client players have extended their client capabilities to recognize multiple standard file types, such as MPEG-1 (.mpg), ActiveMovie/Video for Windows (.avi), QuickTime (.mov) and RealVideo (.rm and .ram). Progressive Networks' G2 Real Player, with plug-in extensions, and Microsoft's Windows Media Player can open and playback multiple digital video file formats, for example.
   
   Additional functionality provided by the client, in collaboration with the server, can include permission to save a file to hard drive, optimization of playback based on network connection (e.g. 28.8 KB, 56 KB, T1, etc.) and auto-selection of video file format for a video asset transcoded in multiple formats, usually based on the bandwidth capability of the client network connection.
   

   Streaming Media Shootout!!! University of Pennsylvania

   Digital Video Magazine