Page 3 of 4: XviD Codec Options: Zones, Advanced and Other Options


XviD: Zones
XviD: Zones

Zones allow you to apply different encoding settings to different parts of the video, for example, applying a lower bit-rate to the end credits to save space. You can use the "Add" and "Remove" buttons to add/remove a zone, and once you select a zone, you can click on the "Zone Options" to configure the zone:
XviD: Zone Options
XviD: Zone Options

Start frame #: - This is the video frame number for which this zone will start to apply. For example, if you credits start at the 181024th frame, then enter it here.

Rate control: - The "Weight" option allow you to specify a weight on the chosen bit-rate. A "Weight" setting of 0.15 will mean the zone will only get 15% of the bit-rate of the main movie. Similarly, a "Quantizer" (the lower the quantizer, the higher the quality) setting can be specified in place of "Weight".

The other options are:
  • Begin with keyframe: This option ensures the zone starts with a keyframe
  • Greyscale encoding: This encodes the zone as black and white only
  • Cartoon mode: This option helps with the encoding of cartoons, but only if these cartoons have certain properties (like lots of static scenary, lack of small details).
  • Chroma optimizer enabled: This helps to reduce the problem of chroma noise, where large patches of red or blue can have random noise and therefore causes macroblocks when the encoder tries to encode these noises
  • BVOP sensitivity: The higher the setting, the more B-Frames will be used
Press "OK" to exit the zone configuration window.

Quality preset/Advanced Options:

XviD: Quality Preset
XviD: Quality Preset

You can access the advanced options by clicking on the "more" button in the "Quality preset" section.

XviD: Advanced Options - Motion
XviD: Advanced Options - Motion

Motion search precision: - This options determines the precision of the motion search algorithm. The higher the setting, the better quality the picture will be (at the expense of encoding time). Set this to "6 - Ultra High" or "5 - Very High".

VHQ mode: - This option enables a more precise motion search mode, but at a serious expense of speed. It is usually not worth going higher than "1 - Mode Decision", unless you have selected the GMC option earlier on.

Use VHQ for bframes too: - Selecting this option will decrease encoding speed by applying VHQ mode to B-frames as well

Use chroma motion: - Selecting this option will decrease encoding speed by about 5-10%, but will improve quality by reducing macro blocks.

Turbo ;-) - This option enables some speed optimization at the expense of some minor quality loss.

Frame drop ratio: - Setting this ratio to higher than 0 will let the encoder drop frames from the encoding, which will seriously degrade the quality of your encoding. Leave this setting at 0.

Maximum I-frame interval: - I-Frames (keyframes) helps you to skip forward/backwards (seek) through the movie (when you skip, the picture has to land on a keyframe first). Keyframe are automatically inserted at scene changes, but in case you have a movie where the scene never changes, then set this to a reasonable value to avoid having no keyframes. For example, you can insert a keyframe every 10 seconds by multiplying the framerate of the movie (eg. 23.976 or 25 or 29.97) by 10 (eg. 240, 250, 300), and entering it here. Keyframes will still be inserted at scenes changes, but if the interval between keyframes (or scenes) is greater than the specified number of frames, then another keyframe will be inserted.

Cartoon Mode: - You can enable this option if your source material is animation.

Now click on the "Quantization" tab.

XviD: Advanced Options - Quantization
XviD: Advanced Options - Quantization

Quantizer Restrictions: - Apart from changing all Min quantizer settings to 2 (using 1 will not improve picture quality, and will only increase file size), you can leave the other settings alone, as the codec will determine the best quantizer values to use.

Trellis quantization: - This option will decrease the file size, but may decrease encoding speed and quality.

Other Options:

Clicking on the "Other Options" button opens up a new window.

XviD: Other Options - Encoder
XviD: Other Options - Encoder

FourCC used: - The FourCC code determines the type of codec that was used to encode the video. Since DivX and XviD are similar (both based on MPEG-4), you could change the FourCC to make it playable with another codec. Normally, leave the FourCC code as it is (you can also change the code in the future if you wish).

Number of threads: - This options was enabled in version 1.2.x of the XviD codec. This allows you to run XviD encodinds in multi-thread mode, to take advantage of dual-core, hyperthreaded or multi-CPU setups. Leaving this at "0" disables multi-threading, and this is the recommended setting. Setting it to 2 might speed up encoding in a dual-core or hyperthreaded system, but certain options (like GMC) are not multi-threaded, so the speed up might not be evident.

Most of the other options can be ignored (eg. the "Decoder" tab sets the default decoder options for the encoding - decoding options can be adjusted during playback as well), but in the "Common" tab, there is an option called "Performance optimization", which allows you to select which CPU optimizations to use (the "Automatic detection" option works fine in most situation). Selecting a CPU optimization when your CPU does not support is not recommended for obvious reasons.



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