Re: TV Glossary
From: Michael A. Dolan (miked@tbt.com)
Date: Tue, Aug 31 1999
Message-Id: <3.0.5.32.19990831165832.00989960@cts.com>
Date: Tue, 31 Aug 1999 16:58:32 -0700
To: www-tv@w3.org (WWW TV List)
From: "Michael A. Dolan" <miked@tbt.com>
Subject: Re: TV Glossary
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At 12:24 AM 9/1/99 +0200, Harald Tveit Alvestrand wrote:
>
>>Program - a collection of related video, audio and/or data in a
>>single "file". This is also generically called "content".
>
>So a Program has a definite, limited size. Right?
Yes. And, and when it is assembled into a Program Stream, it has a
start and end time.
>>Program Stream - as defined in ISO 13818-1 for MPEG - a streaming
>>version of a Program.
>>
>>Transport (Stream) - as defined by ISO 13818-1 for MPEG - a
>>multiplexed collection of concatenated Program Streams without
>>beginning or end.
>
>Query:
>what does multiplexing mean in this case?
>Two possibilities - breaking up a Program Stream to insert other
Program
>Streams (like commercials) - and multiple unrelated Program Streams
being
>transmitted at the same time (for instance normal programming +
teletex)
The latter. It is not so interesting an animal in file-based
systems. DVD "files" are Program Streams. They contain a single
Program along with a single time base. In contrast, Transport
Streams are primarily used for emission by a Broadcaster or Transport
Company and contain one or more Program Streams each with their own
time bases.
>>Content Author - usually a studio (Disney, ABC Studios) that
creates
>>video, audio, and "data" or some aggregation of these.
>>
>>Channel - a Program Stream. This is also known in DVB as a
>>"service".
>
>Now I'm confused; I would have thought that a Channel would be a
Transport
>Stream.
A channel is one Program Stream (analogous to analog TV now - you get
some video, audio and maybe data). A Transport contains one or more
Program Streams multiplexed together. This is like the cable
company, or a digital (DVB or ATSC) system.
>>Network - company that authors and aggregates content and
distributes
>>it (ABC).
>>
>>Transport Company - a company that aggregates and emits (usually in
>>cable or satellite) a collection of channels (DIRECTV). This is
also
>>sometimes referred to as a "network", but usually confuses folks
when
>>it is.
>
>I'll assume that network-owned transport companies can be described
as a
>Transport Company plus a Network, rather than confusing the terms.
Corporate ownership is not a consideration. Otherwise, we'd have to
figure out how make GM car names part of the (DIRECTV) Transport
namespace ;-)
>>Broadcaster - company that emits radio waves (KABC).
>
>Is a Broadcaster always a special case of Transport Company?
It gets more confusing with the new ATSC and DVB-T systems and as
time goes forward with new business models for folks like HBO. I
think the answer is yes, but let's leave them separate for now.
"Boadcaster" has a very special meaning to TV folks, and is thus
worth mentioning as the entity requiring a transmitter license.
>Is a Feed a special case of a Program Stream?
Yes. It is what comes out of a network to the affiliate stations,
and/or Transport companies, but is not output directly by a
Broadcaster. So, it will have only the network ad-insertions, and
will usually be modified in some way (including time-delay) before
final emission.
Mike
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Michael A. Dolan, Representing DIRECTV, (619)445-9070
PO Box 1673 Alpine, CA 91903 FAX: (619)445-6122