Quantization controls
Description
This guide shows how quantization can improve video quality. Quantization is a lossy data compression technique. The encoder includes several quantization controls.
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Adaptive Quantization (AQ):
AQ can reduce smear in high-motion and sports content. It can also improve the video quality on areas that are smooth surfaces.
Recommendation: We recommend that you set this parameter to Auto.
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Spatial AQ:
Spatial AQ can improve video quality in video blocks where distortion would be noticeable. Spatial AQ allocates more bits to those high-risk areas, such as smooth textured blocks. It allocates slightly fewer bits to blocks where distortion won't cause noticeable visual degradation, such as complex textured blocks.
Keep in mind that spatial AQ isn't content aware. The blocks that will receive fewer bits might belong to an object that is drawing the viewer's attention at that moment. Removing bits at that specific scene might not be ideal.
This parameter applies only when Adaptive Quantization is set to Low or higher.
Recommendation: Choose a low spatial AQ for homogenous content, such as gaming and cartoons. Choose high or higher spatial AQ for content with a wider variety of textures.
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Temporal AQ:
It applies fewer bits to areas within the frame that are complex in nature and that are affected by motion. For example, text tickers on newscasts and scoreboards on sports matches. The text characters are highly complex (sharp edges) and they scroll across the screen. Temporal AQ attempts to improve the readability by detecting motion of such complex entities, thus removing possible trailing artifacts.
This parameter applies appears only when Adaptive Quantization is set to Low or higher.
Recommendation: Temporal AQ should almost always be enabled. But keep in mind that temporal AQ might remove bits from some relevant areas of the frame. For example, if enabling temporal AQ on sports matches would make the athletes faces and movements less clear, it might be better to turn it off. On the other hand, for newscasts, you should definitely enable temporal AQ. The parameter helps improve video quality because it removes bits from the news presenters, who are moving less and therefore present less complexity. It adds bits to text tickers that present more comlexity.
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Flicker AQ: This parameter reduces flicker in the video. The parameter might prevent the abrupt change in detail that gives the effect of a flicker in the video.
This parameter applies only to H.264 and H.265, and only when Adaptive Quantization is set to Low or higher.
Recommendation: We recommend that you enable this parameter only when I-frame pulsing is noticeable. Otherwise, let the encoder run its macroblock optimizations freely.
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Framing AQ: Compresses the edges of the video slightly more than the center. The effect assigns more bits to the middle of the image, where the action and the viewer's attention are typically focused. When more bits are assigned, the video quality increases.
This parameter appears only when the output codec is MPEG-2, and when Adaptive Quantization is set to Low or higher.
Recommendation: For low bitrate encodes (for example, MPEG-2 1080i at 10 Mbps), we recommend that you enable this parameter. The visual effect of framing quantization is intentionally subtle.
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Softness: A higher softness value compresses high spatial frequencies more, which reduces bitrate allocation at the cost of image sharpness.
This parameter appears only when the output codec is H.264 or MPEG-2.
Recommendation: For low bitrate encodes (for example, MPEG-2 1080i at 10 Mbps), try values 24 and 32. Then test whether the parameter makes any difference to your content.
Location of parameters
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 > Adaptive Quantization |
stream_assembly/video_description/ where
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| Streams – Video > Advanced > Spatial AQ |
stream_assembly/video_description/ where
|
| Streams – Video > Advanced > Temporal AQ |
stream_assembly/video_description/ where
|
| Streams – Video > Advanced > Flicker AQ |
stream_assembly/video_description/ where
|
| Streams – Video > Advanced > Framing AQ |
stream_assembly/video_description/mpeg2_settings/framing_aq |
| Streams – Video > Advanced > Softness |
stream_assembly/video_description/ where
|
