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MBs and Frames Settings

H.264 Advanced Settings

[Partitions]   [B-Frames]

The Partitions section comprises the following codec parameters:

The partition search and decisions increase the accuracy and thus the quality and compression efficiency of the codec, enabling higher quality output. As a general rule, the more searches types of searches the codec performs on the visual information, the more accurately and efficiently it can predict and encode them. Disabling any partition search and decision options will speed up the encoding process at the expense of the quality.

The 8x8 Transform feature is a very powerful compression technique which acts upon larger blocks of visual information and enables the usage of other high-quality partition options such as the 8x8 Intra search which would otherwise be unusable without the 8x8 Transform. Both of these options increase quality to a significant degree, but the usage of the the 8x8 Transform would make your video High Profile AVC compatible and would break the encoded video's compatibility with Main Profile AVC. Thus you should make sure your device supports High profile AVC, otherwise you might not be able to playback the resulting output video file.

All the Partitions settings can be either checked or unchecked.

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The B-Frames section comprises the following codec parameters:

  • Use as reference allows a B-frame to reference another B-frame. Checking this setting might increase quality slightly because these B-frames can be predicted from one another instead of being limited to the P-frames around them for prediction and at the same time the time of the conversion will also increase. This setting should be activated when using more than 2 consecutive B-frames (See the Max consecutive setting below).

  • Max consecutive indicates how many B-frames will be used consecutively. You can use up to 5 consecutive B-frames, but using 2-3 is the most sensible choice. The possible values vary from 0 to 5. The default value is 0.

  • Adaptive activates adaptive use of B-frames. Without this feature, the codec will always put as many B-frames in a row as set in the Max consecutive field.

  • Bias lets the codec increase or decrease the probability that B-frames are being used. The higher this number, the more frequently B-frames will be dropped in. Setting this parameter to 100, for instance, will force the codec to use the maximum number of B-frames specified in the Max consecutive box - it will be the same as uncheck Adaptive check-box. Setting this to -100 will mean that almost no B-frames are used. For most videos, the optimal number of B-frames will be chosen at Bias value of 0. The possible values vary from -100 to 100. The default value is 0.

  • Bidirectional ME parameter allows the codec to predict some B-frames using motion before and after them. This increases quality of the output video.

  • Weighted bipredictional setting allows B-frames to be predicted more heavily from one P frame or another. It results in more accurate and efficient B-frames, therefore increasing quality.

  • Direct B-frame mode allows B-frames to use predicted motion vectors instead of coding the actual motion, thus saving space and increasing compression efficiency. This setting indicates how motion vectors for B-frames are derived: Spatial uses neighboring blocks in the same frame, which may result in a higher PSNR (it can be used for animated content as it better handles inconsistent motion jumps), whereas Temporal makes use of neighboring frames - which many people perceive as higher quality (better used for real-life content with fluid motion).

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If you are not sure which settings to use you can press the Restore Defaults button to discard the changes and restore default settings.

When ready press the OK button to accept the changes you have made.

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