Implementing Closed Captioning Implementing Closed Captioning for - - PowerPoint PPT Presentation

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Implementing Closed Captioning Implementing Closed Captioning for DTV for DTV

Graham Jones Graham Jones NAB NAB Broadcast Engineering Conference Broadcast Engineering Conference April, 2004 April, 2004

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Agenda

• Terminology
• FCC rules
• Standards
• Carriage of DTV closed captions
• PSIP and the caption service descriptor

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Terminology

• DTV – ATSC broadcast, also cable and DBS
• DTVCC – closed captions for DTV
• CEA-608-B – standard for analog NTSC

captioning

• CEA-708-B – standard for DTV captioning

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Terminology

• Native 708

– DTVCC encoded and transmitted in the 708 format in which they were authored

• Translated or Derived 708

– 708 DTVCC translated from line 608 line 21 legacy captions – Sometimes misleadingly referred to as “upconverted” – Sometimes misleadingly referred to as “transcoded”

• Transcoded 608

– 608 line 21 data may be transcoded to fill required 608 compatibility bytes in the 708 caption distribution

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So, what’s the difference?

608 line 21 608 line 21

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Native 708 Native 708

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Native 708 Native 708

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Translated 708 DTVCC Translated 708 DTVCC – – as encoded as encoded

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DTV caption menu DTV caption menu

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Translated 708 DTVCC Translated 708 DTVCC – – user format user format

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Translated 708 DTVCC Translated 708 DTVCC – – user format user format

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Translated 708 DTVCC Translated 708 DTVCC – – user format user format

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Translated 708 DTVCC Translated 708 DTVCC – – user format user format

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Amended Amended Part 15 Part 15 and and Part 79 Part 79

• f the FCC Rules
• f the FCC Rules

FCC rules for DTVCC FCC rules for DTVCC

Report and Order Report and Order 00 00-

• 259

259 July 21, 2000 July 21, 2000

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Part 15.122 Part 15.122 Decoders for Decoders for DTV receivers DTV receivers Effective July 2002 Effective July 2002 Part 79.1 Part 79.1 Closed captions Closed captions for DTV for DTV programming programming Phased schedule Phased schedule

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FCC Rules Summary

• Since July 2002, DTV receivers with >7.8” screen

height, and STBs, must have caption decoders complying with section 9 of CEA-708-B, with some optional features defined as mandatory

• CEA-708-B is incorporated by reference into the

rules

• STBs with NTSC output must output 608 captions

in line 21

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FCC Rules Summary

• Part 79 now says transmitted closed captions must

reflect the changes in Part 15, i.e. DTV programs must include CEA-708-B captions

• During the transition 708 captions may be

translated from existing 608 caption data

• Multi-channel program distributors receiving

programs with CEA-708-B captions must deliver to the home with that captioning intact No distinction between DTVCC for high definition and standard definition

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FCC Rules – New Programming

1/1/02 – 12/31/03 900 hours/quarter 1/1/04 – 12/31/05 1350 hours/quarter After 1/1/06 100% (some exceptions)

• New digital programming is “prepared or formatted

for display on digital televisions, that was first published or exhibited after July 1, 2002”

• Spanish language schedule leads to 100% by 2010

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Exemptions

• Programs shown 2 a.m.- 6 a.m.
• Commercials no longer than five minutes
• Programs not in English or Spanish
• Local non-news programming
• Some local PBS instructional programming
• Several other program types

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FCC Rules – Pre-rule Programming

1/1/03 – 12/31/07 30% of programming (1/1/05 for Spanish) After 1/1/08 75% of programming (1/1/12 for Spanish)

• Pre-rule programming is that first published or

exhibited before July 1, 2002”

• So DTV services now have the same hourly

captioning requirements as NTSC services

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CEA Standards

• CEA-608-B

– closed captioning and data for line 21 of NTSC signals

• CEA-708-B

– DTV closed captions only for ATSC bitstreams – Defines format of 708 DTV captions, decoders, and encoding of 708 data and 608 compatibility bytes in the DTV bitstream – Other information, e.g. caption service descriptor, parental guidance, and other program information previously carried in VBI, is carried in PSIP

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SCTE Standards

• SCTE 43

– Digital Video Systems Characteristics for Cable TV – Requires DTV captions to be encoded in accordance with CEA-708-B and transported in accordance with A/53B

• SCTE 54

– Digital Video Service Multiplex and Transport for Cable TV – When captions are delivered in A/53B, then the caption service descriptor shall be present in the PMT and in the EIT, if present

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SMPTE Standards

• SMPTE 333M

– DTV Closed-Caption Server to Encoder Interface

• SMPTE 334M

– Vertical Ancillary Data Mapping for Bit-Serial Interface

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ATSC Standards

• ATSC A/53B Digital Television Standard

– Carriage of DTVCC in the ATSC transport

• ATSC A/65B PSIP Standard

– Caption Service Descriptor (CSD)

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Recommended Implementation

708 DTV caption data 608 compatibility bytes Caption service descriptor in EIT (and PMT for cable) All these elements should be carried in the ATSC bitstream For distribution upstream of the ATSC encoder they can be carried in a caption distribution packet (CPD) defined in CEA-708-B

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Caption Encoding and Distribution

• Analog and DTV captions are quite different in the

way they are encoded, distributed, and transmitted

• For NTSC, captions are usually encoded,

distributed, and transmitted on line 21 of the video signal

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Carriage of 708 Captions

• 708 captions for DTV have different methods for

carriage before and after the ATSC encoder. They may be carried:

– in ATSC video user data bits for emission (A/53B) – on serial data link from a caption encoder to the ATSC encoder (SMPTE 333M and Grand Alliance standard) – embedded as CDP in serial digital video VANC for recording and distribution (SMPTE 334M) – multiplexed in an AES3 data stream (SMPTE 337M)

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Carriage of 708 Captions

• 708 captions for DTV have different methods for

carriage before and after the ATSC encoder. They may be carried:

– in ATSC video user data bits for emission (A/53B) – on serial data link from a caption encoder to the ATSC encoder (SMPTE 333M and Grand Alliance standard) – – embedded as CDP in serial digital video VANC for embedded as CDP in serial digital video VANC for recording and distribution (SMPTE 334M) recording and distribution (SMPTE 334M) – multiplexed in an AES3 data stream (SMPTE 337M)

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Encoder embeds CDPs in VANC as per SMPTE 334M Currently used

• nly for 292M

HD signals

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Recording, Processing, Distribution

• VANC captions are “sticky data” and

follow video through most baseband routing and switching equipment

• Care needed with preserving VANC data

through VTRs, servers and production switchers and DVEs

• Data bridges
• Issues of latency

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Compression Distribution Systems

• HD program distribution from networks to

affiliates or member stations typically use compressed video over satellite

– must extract captions from VANC – place in private data PID, or – in A/53B video user data

• IRDs are available that re-insert captions in

VANC for distribution at the station

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Local Station Arrangements

• The written paper shows various scenarios for

handling DTV captions at the station

– 708 captions from the network – Locally generated 708 – Translated from 608 – Up and down video format conversion

• VANC is most common distribution method, but

use of a caption server at the station with local encoding is an alternative

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Caption Input to the ATSC Encoder

• External VANC disembedder

– SMPTE 333M / Grand Alliance interface – Caption service descriptor

• Increasing use of internal VANC

disembedder from 292M video

• An alternative architecture uses a caption

encoder or translator feeding the ATSC encoder direct

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PSIP EIT must contain the caption service descriptor to announce and describe the services present Serial link for 708 data into the 708 encoder

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PSIP and Caption Service Descriptor

• For EITs for future events, CSD will need

to come from program schedule/listing service

• For “current event” EIT and PMT, it is

preferable for CSD to come from the on-air program CDP or live caption encoder

– Actual captions could be different from scheduled captions

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Monitoring

• The written paper discusses various

requirements for 708 caption monitoring

– Presence – Display/functionality – Synchronization – Regulatory compliance

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708 Equipment

• Four known vendors for 708 encoders

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708 Authoring Software

• Coming soon…

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Conclusions

• FCC rules require DTV 708 captions now
• Products are available from several manufacturers
• Make sure your bitstream contains both 708 and

608 data and the CSD in EIT and PMT

• Legal 708 DTV captioning is achievable using

captions translated from 608

• Producers need to move to native 708 caption

authoring

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Sources of Information

• Caption Central

– – www. www.captioncentral captioncentral.com .com

• Closed Captioning Handbook

by Gary Robson, Focal Press

• NCAM – DTV Access Project

– – www.dtvaccess.org www.dtvaccess.org

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DTV Draft House

• Demonstration
• f 708 closed

captioning by NCAM

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SMPTE EG 43 SMPTE EG 43 Trial publication on web site Trial publication on web site www.smpte.org www.smpte.org and for sale on CD and for sale on CD-

• ROM

ROM

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Acknowledgements

• SMPTE
• Gerry Field, NCAM
• John Demshock, WFTV
• Rudy Pruitt, PBS
• Members of the ATSC Closed

Captioning Working Group Thank you gjones@nab.org gjones@nab.org