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