Broadcast Engineering - February 2009 - (Page 36)

Feature Managing aFD AFD Aspect ratio 16:9 Description of HD signal Full frame 16:9 image; not center cut protected Pillarbox 4:3 image from 4:3 originated material Full frame 16:9 image; not center cut protected Full frame 16:9 image; center cut protected Original HD image Description of downconverted SD signal 16:9 letterbox in 4:3 frame Downconverted SD image 1000 1001 16:9 Full frame 4:3 image 1010 16:9 16:9 letterbox in 4:3 frame 1111 16:9 Full frame 4:3 image Table 1. AFD usage for HD to SD downconversion creative control by allowing the audience to view content as the content creator originally intended. The most proven use of AFD is applied at the final stage of production — not on individual production elements. Within this model, the proper AFD code is recorded onto the final version of content as it will be aired, whether it be a live show, recorded program or commercial spot. From an operational standpoint, a predefined downconversion format should be assigned to HD programs or commercial spots through application of the proper AFD code. For live programming produced from a control room, a device can be used to insert the proper SMPTE 2016-3 AFD code into the main program output. This will help to ensure that the proper AFD code is attached to the final version for air and avail- able to all downstream distribution systems. (See Figure 5.) For preproduced programming, a number of options are available for AFD authoring. If the output of the production session is HD-SDI, the same SMPTE 2016-3 AFD insertion described above can be effectively used. For finished content that is delivered via tape (e.g. commercial spots) or baseband video (e.g. from edit rooms), the appropriate AFD data can be authored during the ingest process as shown in Figure 6. Using this model, a process should be established to allow the content providers to select how their HD content should be downconverted. With file-based transfers from NLEs to playout servers becoming more common, AFD insertion in this domain has also been successfully implemented. This production work- flow allows for finished NLE projects to be automatically transcoded and transferred to playout servers without going back to baseband video. As illustrated in Figure 7 on page 37, a completed project can be transcoded and transferred directly to a playout server with the desired AFD code attached. Many HD servers preserve vertical ancillary data space (VANC) on ingest and playout. However, each manufacturer has a proprietary method of storing VANC information in its internal file formats. For this reason, simple file transfers in and out of playout servers may result in the loss of AFD data. Limiting these types of file transfers between the same manufacturer models will help to protect against AFD data loss. File compatibility and VANC preservation must be tested and established. 36 broadcastengineeringworld.com | February 2009 http://www.broadcastengineeringworld.com

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Broadcast Engineering - February 2009 Contents Viewing the Slowdown in 3-D Examine Workflows Tapeless Technology Digital Audio 24p and 25p Judder Video Routing: A Look at What's Next Managing AFD The Right Connections Solid State Logic's AWS 900+ SE and More... Advertisers Index

Broadcast Engineering - February 2009

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