TechTips - Active Format Description (AFD)

Add content Active Format Description (AFD) during encoding


PixelTools products can add content Active Format Description (AFD) headers to your video during encoding or to an existing MPEG stream without transcoding.

Active Format Description is a standard set of codes that can be sent in the MPEG video stream or in the baseband SDI video signal that carries information about their aspect ratio and active picture characteristics.

It is used by television broadcasters to enable both 4:3 and 16:9 television sets to optimally present pictures transmitted in either format. It has also been used by broadcasters to dynamically control how down-conversion equipment formats widescreen 16:9 pictures for 4:3 displays.


Test Drive

Download the AfdTrial.zip to obtain a demo version of MPEGRepairHD that is configured to automatically add Active Format Description headers during encoding.

Unzip the demo file into a directory and run the AFD.bat file to launch the demo. The demo will automatically add the 16:9 Center AFD flags during encoding.  You can view the resultant AFD data in the user_data in the MPEGRepairHD decode statistics window.

Simple Steps

The Active Format Description, specific to your source video, can be added to elementary video user_data during encoding with MPEGRepairHD or ExpertHD. Select the Optimize Encode | Configure | Line 21 dialog to bring up the Active Format Description selection dialog.  Check the Add AFD Flags and select your desired AFD mode from the drop down menu.  During encoding, your selected AFD header will be periodically added to the stream.

The Active Format Description is defined in the ATSC Standard A/53. This header should be included in encoded video when “the rectangular picture area containing useful information does not extend to the full height or width of the coded frame.”


Specifications

The following Active Format Descriptions are supported by PixelTools products:

box 16:9 top 

box 14:9 top

box > 16:9 center

Active format same as coded frame

4:3 center

16:9 center

14:9 center

4:3 with shoot and protect 14:9 center

16:9 with shoot and protect 14:9 center

16:9 with shoot and protect 4:3 center

Active Format Code Inserted

2                box 16:9 top
3                 box 14:9 top
4                 box > 16:9 center
8                 same as coded format
9                 4:3 center
10               16:9 center
11               14:9 center
13               4:3 protect 14:9 center
14               16:9 protect 14:9 center
15               16:9 protect 4:3 center

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MPEGRepairHD and ExpertHD are trademarks of PixelTools Corporation. All other brand names are trademarks or registered trademarks of their respected holders.


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