This is version 2.18 of the AWS Elemental Server documentation. This is the latest version. For prior versions, see the *Previous Versions* section of [AWS Elemental Conductor File and AWS Elemental Server Documentation](https://docs.aws.amazon.com/elemental-server/).

# Encoding – Scan Type
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## Description
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The scan type of content can affect the video quality. The following are the settings and internal algorithms tied to the scan type:
+  The encoding controls that deal with scan type are dealt with in [Image Processing – Scan Type – Key Controls](vq-scan-type-key.md).
+ **Picture Adaptive Field Frame (PAFF)**: This control is automatically enabled on Graphics Processing Unit (GPU)-enabled versions of the software and automatically disabled on Central Processing Unit (CPU)-only versions. 
+ **Macroblock Adaptive Field Frame (MBAFF)**: This control is automatically enabled on CPU-only versions of the software and automatically disabled on GPU-enabled versions. 
+ **Force Field Pictures**: This field appears only if the codec is H.264 and only affects GPU-enabled versions of the software. 
  + **Enabled**: All outputs are forced to use PAFF field picture encoding. 
  + **Disabled**: The encoder switches between PAFF and MBAFF, depending on the content. 

## Recommendations
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+ **Force Field Pictures **results in a significant reduction in quality so it should only be used if required for compatibility with specific decoders or playback devices. 

## Location of Fields
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| Location of Field on Web Interface | Location of Tag in XML | 
| --- | --- | 
| Streams – Video > Advanced > Force Field Pictures |  stream\$1assembly/video\$1description/*codec*/force\$1field\$1pictures where *codec* is: **h264\$1settings**  |