Page 2 of 4: DivX 5.1.x Setup

Select the "DivX Pro 5.1.x Codec" (depending on your version of the DivX codec - eg. "DivX Pro 5.1.1 Codec") in the codec selection section of your video conversion/encoding software. Press the "Configure" button or whatever button that let you configure the codec settings, and you should now have access to the configuration options described below (see screenshot below).

DivX 5.1.x - General Setup

We'll now go through the three major encoding methods (1-pass, 1-pass quality-based and multi pass encoding), and press the links in the steps to find out more about the configuration option. Please also refer to the official DivX guide (large PDF file) for more detailed and technical information on these feature - this guide will provide a quick run through of all the information needed for encoding, while the official guide offers more detailed explanations and technical information.

1-Pass Encoding :

1-pass encoding is the quickest way to encode your video in the DivX format, at the expense of some quality - it allows you to set a fixed average bit-rate to use for the entire encoding. The steps for 1-pass encoding are as follows :

1-Pass Quality-Based Encoding :

1-pass quality-based combines some ideas from multi-pass encoding with the quickness offered by single pass encoding - you get to select the quality of the output (using a constant quantizer setting), as opposed to the bit-rate (which will be adjusted accroding to the quantizer you've selected and the source video). The steps for 1-pass quality-based encoding are as follows :

Multi-Pass Encoding :

Multi-pass encoding is the best way to achieve maximum quality with the DivX format, at the expense of encoding speed. The passes of a multi-pass encoding gathers information regarding the source video and then the subsequent pass use this information to dynamically adjust the size of the output, to get the best ratio between the specified output file size and video quality. Multi-pass encoding includes at least 2 passes. The steps for multi-pass encoding are as follows :

DivX Pro 5.1.x Codec Configuration Reference

Profiles Setup :

1. Open the Profile Wizard
Profiles are pre-programmed settings for the DivX codec that conform to standards set by, hence ensuring maximum compatibility with DivX devices. This will be more helpful in the future, when DivX enabled devices are available, and you want to make sure your DivX encodings will playback on these devices.

To select a profile, click on the "Select Profile Wizard" button.

DivX 5.1.x - Select Profile Wizard
2. Step 1 - Profile Select?
Here, you can select the preset DivX profiles to use. The four profiles currently available are Handheld, Portable, Home Theatre and High Definition, and a description is provided for them in this screen.

DivX 5.1.x - Profiles Setup - Step 1

If you choose "Disable Profiles", this will basically allow you to have access to more options, but at the expense of compatibility.
3. Step 2 - MPEG4 Tools
These options allows you to select the three special encoding methods that will try to improve the quality of the encoding, while decreasing the file size.

DivX's use of profiles limits the use of these tools, and you may only be able to select some of these options if you disable the use of profiles.

Use Quarter Pixel - Quarter pixels increases the resolution of motion search, and hence, will improve quality, especially with the fluidity in motion of objects in the distance. The motion search resolution is increased, the search time will be longer and hence, encoding time will be longer as well.

Use GMC - Global Motion Compensation (GMC) is useful in improving the quality of scenes where lots of movement (especially panning, zooming) occur. You should enable this option. Not available when profiles are used

Use Bidirectional Encoding - Bidirectional encoding allows for the use of B frames in the encoding, in addition to the I-frame (data for this frame is completely stored) and the P-Frame (predicted frame). This option also increases quality, so enable it as well. Not available for the "Handheld" profile
DivX 5.1.x - Profiles Setup - Step 2

4. Step 3 - Profile Validation
If you didn't disable profiles, then you will be able to enter the resolution/framerate of your video. Doing this allows the DivX codec to check that your encoded video will conform to whatever profile/standard you have selected, although it will not affect the actual video encoding.

General Setup :

DivX 5.1.x - DivX Codec General Setup
Performance/quality :
Determines tradeoff between performance and quality. Leaving it as Standard gives you the best possible picture/encoding speed ratio. A setting of Standard correponds to the "Slowest" setting in previous version of the DivX Codec, and this is the recommended setting (the quality gains from setting it to a slower setting may not be worth the trouble). If you really want to use the "Slow" or "Slowest" settings (which uses a new "rate-distortion" algorithm), then use it during the last pass, as otherwise, the encoding will take hours for just a minute of video. Not available when Quarter Pixel MPEG4 mode is selected.
Variable bitrate Mode
Choose the type of encoding method for this codec.

1-pass encoding is similar to DivX 3.11 Alpha's "low motion" encoding, allowing you to specify an adverage bit-rate, which the encode will try to achieve.

1-pass quality-based encoding is basically constant quantizer encoding (same quantizer used for every frame, and the bit-rate will be adjusted to ensure the quantizer/quality level is reached), but you specify the quality of the output, rather than the bit-rate directly. File size, unfortunately, becomes unpredicatable as a result. This option is not available when a profile is selected.

multi-pass is the best encoding option (for smallest file size, and best quality) - multi-pass encoding takes longer than 1-pass encoding : the encoding time is roughly the encoding time of a "1-pass" encoding multiplied by the number of passes (eg. 2-pass takes twice as long, 3-pass takes three times as long ...), but the results may be worth it - multi-pass uses the bitrate you selected as appropriately as possible, to give you both an accurate file size (good if you are using bitrate calculators - make sure you get a DivX 4.x/5.1.x compatible calculator) and the best possible looking picture given that bitrate.

DivX 5.0.3 Pro added Nth pass encoding. Previously, only 2-passes were available. Now, you can have as many passes as you want, with each pass giving the DivX codec more information to work with, and hence, achieve a higher quality encoding (at the expense of time, of course). Note that it is very hard to achieve any noticeable quality improvments after 3-passes.

Using Nth pass encoding is similar to using 2-pass encoding : you have a common first pass using the "Multipass - 1st pass", and then subsequent passes can be performed using the "Multipass - nth pass" settings.

DivX 5.1.x - Variable bitrate mode
Quantizer : - (for "1-pass quality-based" mode only)
The lower the quantizer, the higher the quality. Think of the "%" value given as the quality as defined by a percentage of the original source quality.
Encoding bitrate :
This is the bit rate setting for the video. A setting of 1500 will produce very good quality video (lower will mean a smaller file size, but poorer quality). Don't go below 650 (650-1000 for 1 CD movies), and there is probably not too much point in going over 2000 (1300-2000 for 2 CDs).
Bitrate modulation : - (for "Multipass - nth pass" mode only)
This allows you to tell how much motion your source video has, and let the DivX codec decide on the best way to encode this video source. Drag the slider towards "high-motion" or "low-motion" depending on your source. As an example, an action movie will usually have lots of high-motion scenes (where the camera pans and zooms quickly), and a drama will probably have lots of low-motion scenes. Selecting the right bitrate modulation setting will help the DivX codec to better use available bit-rate.
Multipass encoding log files :
Log file - 2-pass encoding requires the information in the first pass to be stored in a LOG file - you can specify the location to store the log file by using this option. You can also specify whether to write/update this log file (the log file only needs to be updated if you plan on doing another pass after the current pass).

MV file - DivX 5.1.x adds MV files, which contains Motion Vector data. This type of logging is no longer recommended by DivXNetworks.

Video Setup :

DivX 5.1.x - Video Setup

Psychovisual Enhancement :
Just like how MP3 encoding removes bits that the human ear can't hear, to decrease file size, psychovisual enhancement does the same with the video.
Enable Crop :
Cropping allows you to remove a part of the picture that you don't want encoded - for example, the black bars on widescreen movies (they will be added back by your DivX player anyway, so there is no point wasting bitrate on them). Generally, your conversion tool will have a similar feature, so you should just disable and ignore this section.
Enable Resize :
Same deal as cropping, except this is for resizing the overall picture - you should just disable and ignore this section.
Advanced :
Pre Processing Source :
This option should really be renamed to "Noise Reduction", as this is what it really does. Unless your source has lots of noise in it (which shouldn't be the case if you are converting from a DVD), so you should just disable it.
Scene change threshold
This setting determines the percentage of blocks not tracked by the motion search algorithm to trigger a scene change. Leave this at 50%, but if you do need to change it, make sure it is between 40% and 60%. This option is ignored when the "Performance/Quality" mode is set to "Slowest".
Source Interlace :
You can encode the video as progressive or interlaced. If your original source is interlaced, then encoding it as interlaced may result in a better looking picture, although it may increase file size. Similarly, encoding the video as progressive if the source is progressive will be benefitial. There are many ways to check if your video source is interlaced or progressive, but using DVD2AVI and checking for the "Frame Type" is a good way to achieve this.

The last option allows you to "Deinterlace all frames", which is just a way to convert the interlaced source into a progressive one. This is not really recommended, as it can lower picture quality.

DivX 5.1.x - Source Interlace
Max Keyframe interval
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.



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