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Active Format Description
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<h2 id="usage">Usage</h2> <p>A widescreen 16:9 signal may be broadcast with AFD 8 or AFD 10, indicating that the entire frame includes important picture information and should not be cropped. On a 4:3 TV, this will then be shown as a 16:9 <a href="/facts/Letterbox_(filming)/9RyUXoUr">letterbox</a> to ensure no image is lost. Other widescreen 16:9 content (like sports coverage) may be broadcast with AFD 15, indicating that it is safe to display only the central 4:3 region. On a 4:3 TV, the image will be cropped and it will be shown full-screen. </p><p>As of 2006, AFDs are only broadcast in a minority of the countries using MPEG <a href="/facts/Digital_television/KQCyILQa">digital television</a> but used most notably in the UK as required by the <a href="/facts/Digital_TV_Group/ckf7nWyq">Digital TV Group</a> D-Book.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> As a result, the quality of implementation in receivers is variable. Some receivers only respect the basic "active area" information. More fully featured receivers also support the "safe area" information, and will use this to optimise the display for the shape of the viewer's screen. Display in the compromise <a href="/facts/14:9/dnjGRumL">14:9</a> letterbox format was not supported by initial British receivers, which limited the value of the AFD flags - this ratio is especially useful when watching widescreen material on smaller 4:3 sets. </p> <h3>AFD for the DVB DTV transition</h3> <p>The line 23 data format (compatible with the analog <a href="/facts/Widescreen_signaling/I0QFJ1ul">Widescreen signaling</a>) allows signaling of the source (coded image) aspect ratio and the Active Format Descriptor.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <table><tbody><tr><th>Bits</th><th>Format</th></tr><tr><td>000</td><td>Active region same as coded frame (source material)</td></tr><tr><td>001</td><td>4:3</td></tr><tr><td>010</td><td>16:9</td></tr><tr><td>011</td><td>14:9</td></tr><tr><td>100</td><td>not used - reserved for future use</td></tr><tr><td>101</td><td>4:3 with <a href="/facts/Shoot_and_protect/s7gM5YCW">shoot and protect</a> 14:9 center</td></tr><tr><td>110</td><td>16 : 9 with shoot and protect 14:9 center</td></tr><tr><td>111</td><td>not used - reserved for future use</td></tr></tbody></table> <h3>AFD for the ATSC DTV transition</h3> <p>A concerted effort on the part of US broadcasters to broadcast AFD began in 2008 in preparation for the <a href="/facts/DTV_transition_in_the_United_States/fbs2Tp7z">US DTV transition</a> which occurred on June 12, 2009. </p><p>After the DTV transition, 4:3 versions of programming are not available directly from a large percentage of US broadcasters. Cable and satellite providers down-convert 16:9 HD feeds from these broadcasters to generate the 4:3 SD versions for their SD viewers. The most common forms of down-conversion are letterbox or center-cut (cropping off the left and right sides of the 16:9 image to fit into the 4:3 raster). </p><p>Some US broadcasters transmit AFD with their HD DTV signals in order to maintain control over how SD viewers will receive their programming. With AFD included in these signals, cable and satellite providers are able to dynamically control whether HD content is to be either letterbox or center-cut for their SD viewers. However, there are cases where pay-TV providers completely disregard AFD instructions and for instance, present a 4:3 picture with widescreen elements cut off to assuage user complaints about letterboxing, on standard 4:3 sets (for instance for a secondary-market station available only in standard definition on a provider on the claim that an HD signal exists for the provider's 'primary' station for a network), to the displeasure of broadcasters. </p><p>Without AFD, either a fixed letterbox or center-cut will be required on a station-by-station basis. A fixed letterbox will result in an undesirable <a href="/facts/Windowbox_(film)/Tocz1A05">windowbox</a> (i.e., a combination of letterbox and <a href="/facts/Pillarbox/yevMudDe">pillarbox</a>, also called "postage stamp") effect on SD originated programming. A fixed center-cut will result in loss of important picture content on certain HD content (e.g., an HD sports broadcast containing score graphics formatted for 16:9 display). </p> <h3>Complete list of AFD codes</h3> AFD codes<table><tbody><tr><th>Decimal</th><th>Binary</th><th>ETSI<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a><a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> / DVB</th><th>ATSC<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> / SMPTE<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a></th></tr><tr><th>0</th><th>0000</th><td><i>reserved</i></td><td><i>undefined</i></td></tr><tr><th>1</th><th>0001</th><td colspan="2"><i>reserved</i></td></tr><tr><th>2</th><th>0010</th><td>16:9 active picture (top aligned)</td><td><i>not recommended</i></td></tr><tr><th>3</th><th>0011</th><td>14:9 active picture (top aligned)</td><td><i>not recommended</i></td></tr><tr><th>4</th><th>0100</th><td>box > 16:9 (center): wider than 16:9 active picture. The aspect ratio of the source area is not given, and the size of the top/bottom bars is not indicated.</td><td>bar data (indicating the extent of top, bottom, left, and right bars) should be transmitted when using this code.</td></tr><tr><th>5</th><th>0101</th><td colspan="2" rowspan="3"><i>reserved</i></td></tr><tr><th>6</th><th>0110</th></tr><tr><th>7</th><th>0111</th></tr><tr><th>8</th><th>1000</th><td colspan="2"><a href="/facts/Full_frame_(cinematography)/IvA4t42m">Full Frame</a> image, same as the frame (4:3 or 16:9).</td></tr><tr><th>9</th><th>1001</th><td colspan="2">4:3 Image: Full Frame in 4:3 frame, <a href="/facts/Pillarbox/yevMudDe">Pillarbox</a> in 16:9 frame.</td></tr><tr><th>10</th><th>1010</th><td colspan="2">16:9 Image: <a href="/facts/Letterboxing_(filming)/9RyUXoUr">Letterbox</a> in 4:3 frame, Full Frame in 16:9 frame.</td></tr><tr><th>11</th><th>1011</th><td colspan="2">14:9 Pillarbox/Letterbox image.</td></tr><tr><th>12</th><th>1100</th><td colspan="2"><i>reserved</i></td></tr><tr><th>13</th><th>1101</th><td colspan="2">4:3 with <a href="/facts/Shoot_and_protect/s7gM5YCW">shoot and protect</a> 14:9 centre. The term "shoot and protect" is not explained in the standard, but means that the areas above and below the central 14:9 region of the 4:3 active picture can be trimmed without losing important detail.</td></tr><tr><th>14</th><th>1110</th><td colspan="2">16:9 with shoot and protect 14:9 centre. Here, the areas to the right and left of the central 14:9 region of the 16:9 active picture can be trimmed without losing important detail.</td></tr><tr><th>15</th><th>1111</th><td colspan="2">16:9 with shoot and protect 4:3 centre. Here, the areas to the right and left of the central 4:3 region of the 16:9 active picture can be trimmed without losing important detail.</td></tr></tbody></table> <p>The following image illustrates the above codes and the resulting images as seen on 4:3, 16:9 and 21:9 displays. Green circles represent essential content, orange circles indicate optional image areas. Black areas are unused parts of the frame, i.e. bars. The red edge indicates the full frame. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Letterbox_(filming)/9RyUXoUr">Letterbox</a></li> <li><a href="/facts/Shoot_and_protect/s7gM5YCW">Shoot and protect</a></li> <li><a href="/facts/Widescreen/SpJ8gcnV">Widescreen</a></li> <li><a href="/facts/Widescreen_signaling/I0QFJ1ul">Widescreen signaling</a> (WSS)</li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=21480">ETSI TS 101 154 v1.7.1 - the latest version of the DVB standard that defines AFDs</a></li> <li><a href="http://www.etsi.org/deliver/etsi_ts/101100_101199/101154/02.03.01_60/ts_101154v020301p.pdf">ETSI TS 101 154 v 2.3.1 - a newer version of the ETSI standard</a></li> <li><a href="http://www.pjdaniel.org.uk/afd/">AFD codes explained</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Active Format Description (AFD): An Overview (PDF). Tandberg Television. 2008. <a href="https://www.nab.org/documents/resources/paperTandberg.pdf" target="_blank">https://www.nab.org/documents/resources/paperTandberg.pdf</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"EBU QC - Details of 0001W: Active Format Description (v5.1)". qc.ebu.io. Retrieved 2023-03-20. <a href="https://qc.ebu.io/items/0001W/" target="_blank">https://qc.ebu.io/items/0001W/</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"ST 2016-1:2009 - SMPTE Standard - Format for Active Format Description and Bar Data". St 2016-1:2009: 1–21. December 2009. doi:10.5594/SMPTE.ST2016-1.2009. ISBN 978-1-61482-601-9. Archived from the original on June 16, 2018. <a href="978-1-61482-601-9" target="_blank">978-1-61482-601-9</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Daniel, Peter (2020). "Digital Television - AFD codes explained". Peter Daniel. Retrieved 2023-03-20. <a href="https://www.pjdaniel.org.uk/afd/" target="_blank">https://www.pjdaniel.org.uk/afd/</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Finney, Andy. "DTG :: News :: DTG collects Emmy Award". www.dtg.org.uk. Archived from the original on 2012-03-26. Retrieved 2012-01-17. <a href="https://web.archive.org/web/20120326101649/http://www.dtg.org.uk/news/news.php?class=countries&subclass=0&id=4294" target="_blank">https://web.archive.org/web/20120326101649/http://www.dtg.org.uk/news/news.php?class=countries&subclass=0&id=4294</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Finney, Andy. "DTG Publications: D-Book". www.dtg.org.uk. Archived from the original on 2011-10-17. Retrieved 2012-01-17. <a href="https://web.archive.org/web/20111017092559/http://dtg.org.uk/industry/dbook.html" target="_blank">https://web.archive.org/web/20111017092559/http://dtg.org.uk/industry/dbook.html</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"Serial Digital Line 23 - Wide Screen Decoder" (PDF). MICROVIDEO. Archived from the original (PDF) on 2015-01-03. Retrieved 2014-09-25. <a href="https://web.archive.org/web/20150103235404/http://www.divitec.se/sites/default/files/microvideo_wss-dec.pdf" target="_blank">https://web.archive.org/web/20150103235404/http://www.divitec.se/sites/default/files/microvideo_wss-dec.pdf</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>ETSI TS 101 154 V1.7.1 Annex B (PDF). p. 55. <a href="https://www.etsi.org/deliver/etsi_ts/101100_101199/101154/01.07.01_60/ts_101154v010701p.pdf" target="_blank">https://www.etsi.org/deliver/etsi_ts/101100_101199/101154/01.07.01_60/ts_101154v010701p.pdf</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>ETSI TS 101 154 V2.3.1 (2017-02) (PDF). ETSI. January 2017. p. 179. <a href="https://www.etsi.org/deliver/etsi_ts/101100_101199/101154/02.03.01_60/ts_101154v020301p.pdf" target="_blank">https://www.etsi.org/deliver/etsi_ts/101100_101199/101154/02.03.01_60/ts_101154v020301p.pdf</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>ATSC A/53 Part 4 (PDF). Advanced Television Systems Committee. August 2009. <a href="https://www.atsc.org/wp-content/uploads/2021/04/A_53-Part-4-2009.pdf" target="_blank">https://www.atsc.org/wp-content/uploads/2021/04/A_53-Part-4-2009.pdf</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>SMPTE 2016-1-2007 (PDF). <a href="https://www.nab.org/xert/scitech/pdfs/tv110606.pdf" target="_blank">https://www.nab.org/xert/scitech/pdfs/tv110606.pdf</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> </ol>