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 1
Agenda • Terminology • FCC rules • Standards • Carriage of DTV closed captions • PSIP and the caption service descriptor 2 NAB Broadcast Engineering Conference 2004
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 3 NAB Broadcast Engineering Conference 2004
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 4 NAB Broadcast Engineering Conference 2004
So, what’s the difference? 608 line 21 608 line 21 5 NAB Broadcast Engineering Conference 2004
Native 708 Native 708 6 NAB Broadcast Engineering Conference 2004
Native 708 Native 708 7 NAB Broadcast Engineering Conference 2004
Translated 708 DTVCC – – as encoded as encoded Translated 708 DTVCC 8 NAB Broadcast Engineering Conference 2004
DTV caption menu DTV caption menu 9 NAB Broadcast Engineering Conference 2004
Translated 708 DTVCC – – user format user format Translated 708 DTVCC 10 NAB Broadcast Engineering Conference 2004
Translated 708 DTVCC – – user format user format Translated 708 DTVCC 11 NAB Broadcast Engineering Conference 2004
Translated 708 DTVCC – – user format user format Translated 708 DTVCC 12 NAB Broadcast Engineering Conference 2004
Translated 708 DTVCC – – user format user format Translated 708 DTVCC 13 NAB Broadcast Engineering Conference 2004
FCC rules for DTVCC FCC rules for DTVCC Report and Order Report and Order 00- -259 259 00 July 21, 2000 July 21, 2000 Amended Amended Part 15 Part 15 and and Part 79 Part 79 of the FCC Rules of the FCC Rules 14 NAB Broadcast Engineering Conference 2004
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 15 NAB Broadcast Engineering Conference 2004
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 16 NAB Broadcast Engineering Conference 2004
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 17 NAB Broadcast Engineering Conference 2004
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 18 NAB Broadcast Engineering Conference 2004
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 19 NAB Broadcast Engineering Conference 2004
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 20 NAB Broadcast Engineering Conference 2004
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 21 NAB Broadcast Engineering Conference 2004
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 22 NAB Broadcast Engineering Conference 2004
SMPTE Standards • SMPTE 333M – DTV Closed-Caption Server to Encoder Interface • SMPTE 334M – Vertical Ancillary Data Mapping for Bit-Serial Interface 23 NAB Broadcast Engineering Conference 2004
ATSC Standards • ATSC A/53B Digital Television Standard – Carriage of DTVCC in the ATSC transport • ATSC A/65B PSIP Standard – Caption Service Descriptor (CSD) 24 NAB Broadcast Engineering Conference 2004
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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 28 NAB Broadcast Engineering Conference 2004
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 29 NAB Broadcast Engineering Conference 2004
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) 30 NAB Broadcast Engineering Conference 2004
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) 31 NAB Broadcast Engineering Conference 2004
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Currently used only for 292M HD signals Encoder embeds CDPs in VANC as per SMPTE 334M 33 NAB Broadcast Engineering Conference 2004
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 34 NAB Broadcast Engineering Conference 2004
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 35 NAB Broadcast Engineering Conference 2004
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 36 NAB Broadcast Engineering Conference 2004
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