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A Practical Approach To Live Streaming

How to ensure a successful live streaming event.

The web server for video streaming is in no way different from other web servers. The website contains a URL link to the video streaming server —one for every available video stream. Typically this is a link to be selected on the web page.

The systems requesting a video stream over the Internet (or an intranet) must have playback capabilities. Microsoft offers the most commonly used player, but Quicktime (Apple), RealNetworks, and others offer players as well. Some video streaming applications are implemented in such a way as to include the player download in the stream. The players can be downloaded for free.

Making streaming a success

There are five key issues to successful live streaming video, which pertain to live and on-demand events (when content is played back at a later time), including:

  • The most critical part of the webcast is the uplink quality. It must be a continuous, uninterrupted link. It's possible — and common practice — to use the Internet, but it needs to be a broadband link. You can run performance speed tests to verify this link. A good rule of thumb is the bandwidth needs to be at least four times faster than the transmission of your signal (the bit rate of your feed).
  • The second most critical element is production value. Proper lighting, sound pickup, mixing, multi-camera use, and the use of teleprompters when needed are key elements to good production. This can be done with low-cost equipment, including new PDA-driven teleprompters for semi-pro cameras, such as those available from Canon and JVC.
  • Pre-arrange the network uplink with the content delivery network, and test the link in advance of the broadcast. Depending on the vendor, most delivery network producers will provide guidance on test methods, offering the end-user a test board and test feed to ensure everything runs smoothly.
  • Don't use ISDN for uplinks, unless there's no other way. They're always very difficult to work with. Because these links are often misconfigured by the telephone company that provides them, it's difficult to determine exactly what they're capable of. In 2001, ISDN was one of the only uplinks you could get. Today, it's actually one of the least available options.
  • Have before and after content ready to stream to provide some flexibility in the schedule and give participants time to log in and get comfortable.
  • Technology takes great strides

    After much tweaking, live streaming media on the web is easier today than ever to provide and view. Companies, schools, and government agencies are quickly learning the advantages to offering live and/or stored video to their various audiences for live presentations or prerecorded material.

    The fact that streaming media via the web is a fast, cost-effective way to provide direct contact to various constituencies means the demand will continue to grow. No other technology offers such a rich, convenient means for a host of entities to deliver their message. That's why systems integrators and pro AV content producers should embrace the technology, allowing it to take them as far as they can go.

    CURES FOR COMMON LIVE STREAMING CHALLENGES

    Despite the evolution of easier-to-install systems, problems do occur. Here are some of the most common problems — and their solutions:

    Audio and video is out of sync. Audio/video capture cards perform audio/video capture only. AV synchronization is performed by the application. There are a few possible issues of the source video device that could result in an application having AV sync problems. During capture, the audio/video capture card locks to the timing of the incoming source signal. This allows the card to properly time the video and audio sampling, which are taken together. If the source video signal is unstable, or if the source is switched between different sources during capture (and those sources aren't locked to a common clock), then AV sync loss can occur. You may need to place a time base corrector (TBC) or frame synchronizer between the source and the card input to correct these problems.

    For some cards, when capturing from digital sources via SDI, DV, etc., the sampling rate of the audio must match the sampling rate of the source. Some cards also require that when capturing from digital source via SDI, DV, etc., the source must be started before the card starts capturing.

    Is it possible to extract TeleText captioning from a PAL source — as it is to extract closed captioning from an NTSC source with the audio/video capture cards? Closed captioning (CC) is specific to NTSC only. The PAL standard doesn't support CC. Instead, PAL supports a scheme called TeleText, which is transmitted through the source video in the vertical blanking interval (VBI) part of the analog signal. Most cards capture this part of the signal, and output the raw VBI data from any analog source connected to it, from which TeleText (or any other kind of data that happens to be there) can be extracted. Processing of raw VBI data into the desired form requires a custom application. The format of the data isn't defined by the card but by a published specification, an application or third party, etc. Raw VBI data is captured on most cards in both NTSC and PAL modes.

    No audio is recorded. This could be related to the primary card preferences in the Windows control panel. To make certain that the audio/video capture card is the preferred recording device in Windows, do the following:



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