3) The Decoder Configuration Utility

The Decoder Configuration Utility

If you play DivX video using third-party media players, use the Decoder Configuration Utility to adjust settings affecting playback performance. To access this, go to your Start menu and under All Programs select DivX > DivX Codec > Decoder Configuration Utility.

From the “Decoder” tab, checking the box to “Reduce CPU spikes using one frame delay” will help if you are experiencing stuttering during playback, especially on older computers when playing high definition. Selecting to “Output YUV 4:@:0 when supported” can improve playback performance as well, but this feature is not available for all graphics cards.

The “Playback” tab also has various adjustments affecting playback performance. Because of the way DivX compresses images at very low bitrates, phenomena known as “blocking” and “ringing” can sometimes be seen in the picture during playback. Where blocking becomes visible you may begin to recognize that the picture is actually composed of a lot of small squares that move around as the video plays. Ringing is typically most visible around highly contrasting edges in the picture. Where ringing occurs it is possible to see subtle bands of color around the contours of these edges. You’ll see the following choices when customizing your playback configuration:

• Automatic Deblocking is a post-processing technique applied by the decoder on the fly to reduce the blocking effect, helping to blend adjacent blocks together smoothly.
• Custom Deblocking lets you set, from minimum to maximum, the amount of deblocking you wish to apply..
• Full Deblocking with Sharpening automatically adjusts the post-processing level so that your system always applies the maximum possible post-processing during playback. When “Full Deblocking with Sharpening” is enabled it may be a strain on your CPU power.

Setting the post-processing level to “OFF” is recommended for very old computers. On more recent computers, this should normally be set to “Automatic Deblocking” to instruct the decoder to deblock as much as the CPU can support without compromising playback quality.

Disabling some of the setting in “Picture Properties” or “FilmEffect” can also improve playback performance. Most graphics cards also allow you to adjust video color using overlay controls. To do this, go to the Display Properties > Advanced Settings of your Control Panel.

Decoder configuration suggestions for H.264

Similar to the Decoder Configuration Utility for standard DivX codec properties, the H.264 Decoder Config allows you to adjust the properties of the decoder on your system once the DivX software has been installed. To access, open your Start menu and go to All Programs > DivX > DivX H.264 Codec and select the H.264 Decoder Config option.

A new window will appear for Decoder Properties that can be adjusted manually. Here’s a brief run-down on what option can be set:

• Deblocking: Deblocking should normally be on for H.264 video because the encoder assumes that the decoder will perform in-loop deblocking in accordance with the format specification and codes the video accordingly. Turning off deblocking will therefore introduce artifacts during playback, but because deblocking is computationally expensive, this option can be desirable for low-powered systems that could not normally decode H.264 or where battery life is at a premium. Disabling deblocking does not look too bad with most content. Deblocking is enabled by default.
• Multithreading: When enabled, this option allows the decoder to subdivide the decoding process across multiple CPUs or cores to accelerate decoding and provide a smoother playback experience. Multithreading is enabled by default.
• Low latency: This is an experimental feature that may increase the frame rate for more basic bitstreams at lower resolutions, or on systems with larger CPU cache. Low latency is enabled by default.
• Disable logo: Turns off the small DivX logo that appears in the lower-right of the picture for a few seconds at the start of playback. Disable logo is disabled by default.
• Use default encoding settings in this application When this decoder filter property page is accessed from within a host application, this setting instructs the decoder to turn off features such as color correction and the logo overlay and turn on features such as deblocking to ensure that DivX video sources are processed in their original form without any adjustments applied. This is important when transcoding for example. This option is disabled by default and is set on a per-application basis.
• Brightness, Contrast, and Saturation: These sliders enable image adjustments that may improve the appearance of H.264 video on your computer. Each slider is centered by default.