# Miscellaneous video tuning parameters
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## Description
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This section describes individual encoding parameters that provide let you tune the video quality.
+ **CABAC**: Applies only to H.264, and only when the **Profile** parameter is set to **Main** or **High**. This parameter enables arithmetic coding and can compress the same data with approximately 15% fewer bits. As a result, encoding is more efficient. There is no impact on video quality.

  Recommendation: Always enable this parameter unless the intended decoder or playback device doesn't support it. 
+ **Density vs Quality**: Applies only to H.264 and H.265. This parameter sets the balance between density on the appliance and video quality. 
  + A value above **0** favors density over quality. This means that as you add more events to the appliance, the point will be reached where the encoder automatically starts to lower the video quality in any events that has this parameter set above 0. 
  + A value below **0** favors quality over density.

  Note that this parameter controls density and quality, even though the parameter name in the XML is **svq** (speed vs quality).

  Recommendation: On newer appliance models (L8xx and later), we recommend that you leave the default. On older appliance models, a different value might change the balance. However, never use **-2** or **-3** with H.265.
+ **Lookahead**: Lookahead indicates that the encoder should analyze a few frames into the future of the currently encoded frame, to allow the encoder to take future frame data into account during rate control logic. For example, if future frames are more complex, the encoder can allocate fewer bits to encode the current frame. In this way, the unused bits can be used to encode those future frames. 

  The tradeoff of a higher lookahead is that processing and latency increase slightly, to allow the encoder to analyze those future frames.

  Recommendation: Set to **Medium** unless latency is critical.
+ **Profile**: Applies only to H.264 and H.265. For H.264, the profile affects video quality. For H.265, the profile sets various characteristics of the video.

  Recommendation: With H.264, use **High Profile** to achieve higher video quality.
+ **Slices**: Applies only to H.264 and H.265. This parameter improves speed of encoding. Using a higher number of slices can improve speed optimization. However, this results in slightly lower video quality. 

  Recommendation: 

  Set to **Auto** so that the encoder uses a value appropriate to the image height (resolution). The following table specifies which value the encoder will assign when you choose **Auto**, based on the image height.     
[See the AWS documentation website for more details](http://docs.aws.amazon.com/elemental-live/latest/ug/vq-miscellaneous-tuning.html)

## Location of parameters
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This table shows where the parameters mentioned in this section are located. The first column shows the location on the web interface. The second column shows the location in the event XML.


| Location of parameter on web interface | Location of tag in XML | 
| --- | --- | 
| Streams – Video > Advanced > Lookahead | stream\_assembly/video\_description/{{codec}}/look\_ahead\_rate\_control<br />where {{codec}} is one of the following:[See the AWS documentation website for more details](http://docs.aws.amazon.com/elemental-live/latest/ug/vq-miscellaneous-tuning.html) | 
| Streams – Video > Advanced > Profile | stream\_assembly/video\_description/h264\_settings>/profile | 
| Streams – Video > Advanced > Level | stream\_assembly/video\_description/h264\_settings>/level | 
| Streams – Video > Advanced > CABAC | stream\_assembly/video\_description/h264\_settings>/cabac | 
| Streams – Video > Advanced > Slices | stream\_assembly/video\_description/{{codec}}/sliceswhere {{codec}} is one of the following:[See the AWS documentation website for more details](http://docs.aws.amazon.com/elemental-live/latest/ug/vq-miscellaneous-tuning.html) | 
| Streams – Video > Advanced > Density vs Quality | stream\_assembly/video\_description/{{codec}}/svqwhere {{codec}} is one of the following:[See the AWS documentation website for more details](http://docs.aws.amazon.com/elemental-live/latest/ug/vq-miscellaneous-tuning.html) |