Dr. DivX User Guide

What is Dr. DivX, what can it do, and how is it used?

Overview

Handsome Mug of Dr. DivX

This document is the User Guide for the Dr. DivX software, specifically version 2.0.0 Final from Aug 3, 2006. To use Dr. DivX, you'll need the DivX codec which is not included but is available for free. You'll also probably want the free DivX player which isn't required but it is the best way to view your video files.

With the DivX codec installed, you can also use Windows Media Player to view DivX videos although not all DivX features will be supported. Give the official DivX player a try. It's swell.

Installation

Dr. DivX takes residence with very little fuss. Simply run the Dr. DivX installation program. If you have previous versions of Dr. DivX installed, there is no need to remove them. The installer will replace older versions as needed.

You may see a brief progress display while the installer loads. You will then be prompted to select a language. English is the default choice but if you prefer another dialect make your selection using the drop down list and press the OK button. You can always change the doctor's language later. Look at the Preferences section for more details.

After choosing a language, you'll see the Dr. DivX splash screen. This page doesn't do anything but showcase the doctor's handsome mug and pass on some trademark claims in fine print. Click the Next button and move along, nothing to see here.

The next page you'll encounter is the License Agreement. Read the terms carefully. You might find Waldo. Even if you don't, it's a riveting read. If you have no objections with the Dr. DivX license, click the I Agree button to continue your journey.

You will next be pestered to choose the components you'd like to install. There's really not much choice to make although if you don't want the Dr. DivX icon placed on your desktop then uncheck the Desktop shortcuts box before you click the Next button.

The last choice you need to make is for the Installation Location. By default, the doctor chooses a home in the DivX program directory. You can move it if you'd like but there is probably no need for such antics. As long as you can live with the default choice, press the Install button and enjoy the show.

Assuming all goes well, various progress bars will flash by and you'll be notified that the installation is complete. When you are done staring at the Installation Complete page, press the Finish button and it will simply vanish.

You probably want to have a quick look at what you've just installed. Move on to the Quick Start section for the nickel tour.

Quick Start

Choosing an Input File

Choosing an Input File

The quick start guide will talk you through the following steps:

  1. Start Dr. DivX
  2. Press Open and choose a video file to convert
  3. Press Encode to see your choice queued up for conversion
  4. Press Resume to start the encoding
  5. Press Play to view the results

Creating your first DivX file is a snap with Dr. DivX. Look on your desktop for the Dr. DivX icon to launch the program or look on your Start menu under All Programs->DivX->Dr. DivX...

Once the doctor is up and running, press the Open button next to Input file(s). Find your way to any old video file you have laying around. You might want to pick a short one just to test things out.

Dr. DivX will do a quick analysis of your file. There's no telling how long the analysis will take. It will depend a lot on the size of your file and the speed of your computer. However, the doctor will display a progress bar to let you know that the analysis is underway. Short videos on fast computers will be analyzed in a few seconds.

All kinds of buttons will light up in Dr. DivX after the quick analysis is complete. You may also notice a much slower analysis progress bar working in the background. There's no need to wait for the slow analysis. After all, this is supposed to be a quick start.

Some video files may come with multiple audio tracks. You can selectively choose one or more of them from the Audio track(s) list. Likewise, not all videos include subtitles but those that do will allow you to choose one or more subtitles to include. By default, you will get all audio tracks and all subtitles.

A DivX certified profile such as Home Theater will be selected along with Balanced quality. Assume these are fine for now and just leave those settings as they are.

Dr. DivX will automatically choose a Title based on the name of the file you selected. You might want to change that title or at least mentally note what the doctor decided.

File and Batch Icons

Press the Encode button and you'll be transported to the Batch page. You can flip back and forth between the batch page and the file page using the batch and file icons on the toolbar across the top.

If this is your first time using Dr. DivX, the first and only line in the Jobs window on the Batch page will show the name of the input file you selected, the name of the output file that will be created, and the current status of the conversion. The status will probably be Waiting or something similar.

Find and press the Resume button in the Jobs window. Then go make some popcorn. It might take a while. The status will change to Running and a progress bar will start grinding away in the Job Status window. Dr. DivX tries to estimate how much remaining time will be required to complete the conversion, but this isn't an exact science. The doctor is known to make some pretty awful guesses at first, but usually a more precise estimate appears shortly.

During a quick test while writing this document, Dr. DivX took about 6 minutes to encode a 5 minute long, high quality video on a fairly average PC. The resulting file was 4 times smaller than the original but visually looked about the same. Your mileage may vary.

When the conversion is complete, a Play button will appear in the Job Status window. Press the Play button to start the DivX Video Player and see your new video. If you are happy with the result, don't forget to delete the original input file which is probably just wasting precious space on your computer's hard drive.

What is it?

Dr. DivX is a cosmetic surgeon for your video collection. The doctor takes almost any frumpy old video file you have laying around and converts it into a sharp, lean mass of multimedia joy.

Audio/Video files are compressed using a codec. There are countless codecs to choose from although you usually don't make a conscious choice. You probably already have a bunch of video files encoded with a variety of codecs. The doctor will convert that mess into a library of tightly encoded DivX video files.

There are lots of reasons why everyone clamors for a library of DivX video files.

  1. Due to all the poorly crafted codecs and players out there, lots of videos don't play very well. Dr. DivX can usually convert those to high quality versions that play back very smoothly and reliably.
  2. Watch your videos on any computer! DivX compatible players are available on a wide variety of platforms including Windows, Mac OS X, Linux, Palm OS, and Pocket PC.
  3. Watch your videos on the go! With the right software, lots of mobile devices can play DivX video files including many cell phones and PDAs.
  4. Watch your videos on your TV! There are many, surprisingly affordable DVD players on the market that easily connect to your television and playback DivX videos superbly. Just copy your DivX videos to a CD, DVD, memory card, or USB drive.
  5. DivX files support features like multiple audio tracks, subtitles, chaptering, and interactive menus just like you find on a snazzy DVD.

File

The Dr. DivX File page has three basic parts. There is the ever-present preview window on the right hand side of the page. There is also a basic or an advanced window on the left hand side. You can switch between basic or advanced using the tabs at the top of the window.

Before delving into those parts, take a look at the buttons labeled Encode and Save Encode Settings along the bottom of the File page.

Encode

The ominous Encode button has already been mentioned a couple times. Once you've picked an input file and tweaked all the options, press the Encode button to queue up your video for batch processing. When you press encode, you'll be whisked over to the Batch page. Don't worry; you can always flip back and forth between the File page and the Batch page using the buttons on the toolbar near the top of the page.

Save Encode Settings

The Save Encode Settings button is for the Custom Profile feature. Not surprisingly, the button will allow you to save your encoding settings. Dr. DivX will show you a drop-down list of all the other custom profiles you've created. You can either replace an existing profile or type in a new name.

Preview

The Preview Window

The Preview window has no title and it doesn't play videos, but it will display frames from the input file. This will give you some idea of how the output video will appear once it's been cropped and scaled. The preview will be cropped according to the settings found in the Advanced window.

It can take a few minutes for the doctor to figure out where all the frames are in your video file. While performing the necessary calculations, Dr. DivX will display a progress bar labeled Analysis above the preview window. When the analysis is complete, the preview picture will be displayed.








File Title and Output

Dr. DivX will automatically choose a Title based on the name of your input file. The title will be used as the name of the output file created by Dr. DivX. You can use any name you'd like as long as it's a valid file name. The doctor always adds a .divx file extension.

Next to the title is a button to choose the output folder. Click on this button to select the destination folder for the output file. If you don't make a choice, Dr. DivX will use the output folder specified on the Preferences page. See the Preferences section for more details.

File Type, Genre, and More

Theoretically, Dr. DivX can embed some notes in the output file so you can classify videos by different type or genre. However, you might notice that these options are currently grayed out. You can't change them. Someday this feature will be available, but for now, you'll have to wait. Don't worry; these settings are just your own personal notes. Your choices here make no difference to the doctor at all. You can safely skip over these options.

Preview Controls

There are five preview controls under the preview display. Starting from the left, you'll find a skip backward button which jumps the video back a few seconds. Next there is the slow motion forward button which moves the video forward just one frame at a time each time you click on it. If you hold the button down, the video will advance in slow motion. To the right of that is the skip forward button which jumps the video forward by a few seconds.

The horizontal slider may be dragged left or right to quickly move through the video. Unfortunately, the preview slider may not work for all videos. Dr. DivX doesn't give any indication that the slider isn't working. However, if it doesn't respond when you try to drag it around, then it's not working. Don't be alarmed.

Finally, on the far right is the full size preview button. Press this button to open a new window which displays frames at full size. The full size preview controls work exactly like the normal preview controls, although you'll notice the addition of a check box labeled Free. If you check the Free option, you can expand the preview window and adjust the aspect in case you want a closer look.

Preview Information

Under the preview display, you'll find some details about the video file that will be created although it can take a few minutes for the doctor to figure out the preview information. While performing the necessary calculations, Dr. DivX will display a progress bar labeled Analysis above the preview window. When the analysis is complete, the preview information will be displayed.

The preview information includes the length of the video and the target resolution in pixels. The preview information also provides estimates for the resulting file size and the final frame rate. You'll find that audio bitrate and the video codec bitrate have the greatest affect on the resulting file size. Typical files will be 90% video and 10% audio so between the two, the video codec bitrate is the dominate factor.

By adjusting the audio bitrate and the video codec bitrate, you can trade off quality for smaller file sizes. Lower bitrates make smaller files but also don't look or sound as good. Make your bitrate selection in the Advanced window under the Audio tab and the Codec tab.

In practical use, audio bitrates over 128 kbps sound good and video codec bitrates over 1300 kbps look clear even on big screen TVs. You'll certainly find them better looking than your average television broadcast anyway. If you are encoding files for small screens like PDAs or phones, you may want to run the audio bitrate down to 64 kbps and the video down to 150 kbps. The result looks pretty decent on 3 inch displays and an hour of video is only slightly more than 100 Meg in size.

Basic

The Basic Options Window

Half of the File page is devoted to either the Basic or Advanced options window. Use the tabs at the top of the window to flip between the two. If you ask the doctor to perform the same job every time, you can usually create a custom profile that is easily invoked from the Basic window. That should spare you from having to venture into the Advanced options very often.












Input File(s) Open

You can drag and drop a file almost anywhere near the Input file list box. You can also click on the Open button or press Ctrl-O on your keyboard to browse for the input file you want.

Despite the way it looks, the doctor only works on one file at a time except for multipart VOB files (see below). Just drop one file at a time into Dr. DivX, choose your options, press the Encode button, and only then move on to the next patient.

Every time you open an input file, Dr. DivX will setup the default encoding settings that you selected on the Preferences page. If you have a favorite recipe of encoding settings, use the Save Encode Settings feature to save yourself some typing.

Input Multiple VOB

Sometimes video files are broken into multiple parts. This is often the case with VOB files (Video Object files) that you find on DVDs. Dr. DivX is trained to handle multi-part VOBs. All you need do is select all the parts. Use the Open button, browse for the VOB files, and then select all of them. The doctor will put them in the right order based on the file names. Usually the names are something like VTS_01_1.VOB followed by VTS_01_2.VOB and so on.

There's no need to throw in other files like VTS_01_0.IFO. The doctor only knows how to deal with VOB files.

Audio Track(s)

Some video files, like VOBs, can include multiple audio tracks. Just like snazzy DVDs, DivX also allows for multiple audio tracks, so the doctor lets you choose which audio tracks should be included in the output file. If you are not bilingual or you are space conscious then you probably only want one audio track. Either way, just check off the tracks you want included in the output file.

Audio Track Playback

To help you figure out what language option to set for each audio track, Dr. DivX provides some playback controls you can use to preview the selected audio. Simply press the play button to hear some of the track. You can also jump forward or backward a few seconds if you need to skip around a bit.

Audio Track Selection

Next to the Audio Track(s) list, there is a Select button which allows you to specify the order which the audio tracks will be included in the output file.

As you check off each track on the Select Tracks list, you can also specify the track language and caption code from the drop down lists near the bottom of the window. Your choices here don't really matter as far as the doctor is concerned, but when later decide to playback your DivX file, you'll be able to tell which track you want to listen to based on the choices you make here.

Subtitle Track(s)

[This might sound familiar.]

Some video files, like VOBs, can include multiple subtitle tracks. DivX also allows for multiple subtitle tracks, so the doctor lets you choose which subtitle tracks should be included in the output file. If you are space conscious then you probably don't want any subtitles. Either way, just check off the tracks you want included in the output file.

Subtitle Track Playback Controls

The rewind, play, stop and fast forward buttons on the Subtitle Track Selection page are always grayed out. They don't do anything. They are decorative.

Subtitle Track Selection

Next to the Subtitle Track(s) list, there is a Select button which allows you to specify the order which the subtitle tracks will be included in the output file.

As you check off each track on the Select Tracks list, you can also specify the track language and caption code from the drop down lists near the bottom of the window. Just like the audio tracks, your choices for the subtitle tracks don't really matter, but when you later decide to playback your DivX file, you'll be able to tell which subtitles you want to read based on the choices you make here.

DivX Certified Profiles

Select a DivX Profile

As the DivX codec grew into a popular standard, hardware manufactures realized its potential in the consumer market and developed devices claiming to be DivX Compatible.

In truth, these players would typically support only some versions of DivX and even then only limited features from those versions. The capabilities of hardware devices claiming DivX compatibility varied so widely that it became a hit-and-miss affair attempting to encode DivX video that could be played consistently well on all of them. That's why DivXNetworks designed a system of profiles for DivX Certified devices.

By selecting one of the four available profile modes, you instruct Dr. DivX to constrain to the minimum capabilities of devices certified for that profile. Encoder features unsupported by any given profile will be automatically disabled and the encoder will produce only video streams suitable for the certified device.

If you are particularly interested in the technical differences between the minimum requirements of the standard profiles, you'll find all the gory details in the following four sub-sections.

Handheld

  • 176 x 144 at 15 fps
  • 1485 macroblocks per second
  • 200 kbps average
  • 800 kbps peak
  • 32 KB buffer

High Definition

  • 1280 x 720 at 30 fps
  • 108000 macroblocks per second
  • 8000 kbps average
  • 32000 kbps peak
  • 768 KB buffer
  • Bi-directional encoding
  • Optional interlaced video

Home Theater

  • 720 x 480 at 30 fps
  • 40500 macroblocks per second
  • 4000 kbps average
  • 8000 kbps peak
  • 384 KB buffer
  • Bi-directional encoding
  • Optional interlaced video

Portable

  • 352 x 240 at 30 fps or 352 x 288 at 25 fps
  • 9900 macroblocks per second
  • 768 kbps average
  • 4000 kbps peak
  • 138 KB buffer
  • Bi-directional encoding

Quality

Encoding Quality Setting

The Quality setting provides an easy pick for rushed users. Save yourself a bunch of reading by simply choosing Balanced quality and press the Encode button. Now you can skip ahead to chapter 3.

Still here? You may have noticed that Dr. DivX chose a set of advanced encoding options that produced a decent quality video in a reasonable amount of time. It's not the best that DivX can do, but you won't lament about wasting your youth watching a progress bar labeled, encoding.

Would you rather get the best possible picture and you don't care about how long it takes? Move all the way down the options to the Insane Quality setting. On the other hand, if you are really pressed for time, set the quality to Fastest and Dr. DivX will work as quickly as possible. The resulting video may not look stellar, but you'll get it quick.

With 6 levels of quality to choose from, you can test exactly how patient you are. If you want it bad, you'll get it bad and the worse you want it, the worse you'll get it.

Constrain to Fixed Size

You may have realized by now that most video files are not small. Movies are huge chunks of data compared to almost everything else on your computer. In fact, this user guide is about a thousand times smaller than your typical film.

Storing lots of DivX files may be a challenge for you, so Dr. DivX provides the file size constraint to help you out. Just tell the doctor the maximum size you can tolerate and Dr. DivX will choose the right mix of settings to get the best quality video possible without exceeding your size limit. This is particularly handy if you are trying to squeeze a movie on to a 128 Meg memory card or if you'd like to burn a two hour film onto a 700 Meg CD.

Someday, Dr. DivX will allow you to split your videos into multiple files. You see, some folks would like to store long movies on CDs but they find the quality is a tad disappointing if the entire film is limited to 700 Meg. Output file splitting is just what they need. For example, most feature length movies can be divided into 2 files of less than 700 Meg which can then be burned onto two CDs. Unfortunately, this feature is not currently implemented in Dr. DivX so the file count is always 1 and you can't change it.

Custom Profile

Saving a Custom Profile

If you fancy yourself a video connoisseur, then simply picking from a pile of default options will never suffice. That's why Dr. DivX features custom profiles. Whip up your favorite recipe of advanced settings and then use the Save Encode Settings button to create your own custom profile. The doctor will store your settings in the Profile Folder. Then you can apply them over and over again with just a few mouse clicks

Advanced

Under the Advanced tab you'll find even more tabs that divide the settings into four sub-groups called Video presets, Pre-processing, Codec, and Audio.

Advanced Video presets

Video Presets

You can waste away your years tinkering with all the settings under the Advanced tab, but Dr. DivX trys to simply things for you. Stick with the Video presets tab and just move the slider left or right until you find the settings you'd like. The doctor tries to make a tradeoff between speed and quality depending on where you place the slider. There's a good chance one of the many presets will be adequate for your needs.

If the presets don't look tempting enough for you, then uncheck the Use presets checkbox and proceed on to the other three advanced tabs. You are sure to find more settings then you'd care to look at.



Advanced Pre-processing

The Pre-Processing options are split into three boxes named Crop, Resolution and Image Processing.

Crop

Automatic Crop Example

The Crop box does not refer to vegetables. It's a technical term that folks use when they cut up pictures. If you check the Enabled box, you can shave unwanted borders off your input video. There are many reasons why you might want to trim the picture down a bit. For example, you may be planning to watch the output video on a tiny cell phone with a square display. In that case, you could trim some columns of pixels off the left and right so you end up with something that fills the screen of your phone.

It's also quite common to see letter boxed videos that include black borders along the top and bottom of every frame. Dr. DivX will happily encode the black borders that appear in the original source. However, that just makes your output file larger and doesn't really enhance your viewing pleasure. You are probably better off trimming down the top and bottom.

Videos with borders are so common that Dr. DivX includes an Automatic Crop option that does the math for you. Instead of manually counting the number of pixels you need to crop, just check the automatic button. The doctor will figure out where the black borders are and dutifully trim them out.

You'll find the automatic setting works great most of the time, but keep an eye on the results in the preview window. Sometimes videos don't provide a sharp break between the border and the picture. If the video contains pictures that kind of fade into the border, Dr. DivX will have a hard time automatically finding the best place to crop. You may have to manually adjust the crop settings to ensure you've eliminated every row of black pixels.

What's the big deal? Why worry about a few rows? In fact, why not just leave all black borders exactly where they are? The answer is rooted in the way video compression algorithms work. The DivX codec achieves miraculous compression ratios by eliminating tiny details that you don't notice. It turns out that encoding thin black lines is tough. Your output files will be measurably larger and/or your picture quality will be noticeably worse if you keep borders on every frame.

Image Processing

Image Processing Options

As if pounding your videos into different resolutions isn't enough, Dr. DivX offers a few advanced image processing options for you. The Image Processing box really dives deep in to the voodoo of video compression. Don't worry; the following sections describe these options in fairly plain language.



Noise Reduction

The noise reduction filter attempts to smooth out grainy images. This usually makes it easy to compress videos but it can also make the images appear flat. Dr. DivX can perform various degrees of noise reduction from Light to Extreme or you can just leave the option Off.

Quantization

When encoding video, Dr. DivX looks at differences in small blocks of pixels and basically rounds them off to a set of predefined thresholds. This process is called Quantization and it is a key step in achieving the high compression ratios that DivX delivers.

There are two sets of Quantization thresholds available. The old-timers may prefer the original H.263 collection. However, the first H.263 quantization values were later optimized and Dr. DivX recommends you try the H.263 Optimized set.

Interlace

Interlaced video attempts to make motion appear smoother by alternating between two frames on every other line of a display. Usually this appears like jagged edges when you slow the video down and look at one frame at a time. At full-speed on a standard television, the video will look pretty good so Dr. DivX will create interlaced videos if you'd like. However, for high definition televisions and computer monitors you'll want to stick with the Progressive Output setting which does not interlace frames.

Psychovisual Enhancements

Psychovisual Enhancements is based on visual property of Just Noticeable Difference (JND). When Psychovisual Enhancements is not off, Dr. DivX will analyze each frame and concentrate on areas that are more noticeable to the human eye. These are areas of high contrast, while large areas of low contrast are averaged out and the number of colors is reduced. Usually, this results in smaller file sizes and an overall increase in visual quality of the movie. It also means that the encoding process will take a bit longer.

Other than off, there are two settings available for Psychovisual Enhancements. Shaping attempts to enhance fine details in the texture and mask differences between the source and encoded video in complex textures, which make them much less noticeable. In other words, it shapes the texture based on certain parameters.

Masking uses a slightly different algorithm, whereby each block in the frame and the surrounding blocks are analyzed such that the psychovisual enhancement introduces minimal artifacts.

While it's a matter of personal choice, generally shaping produces better results in almost all circumstances. Masking may be more visually pleasing for anime videos.

Resolution

Resolution Settings

Except around New Year's Eve, resolution refers to the number of pixels that are used to make each frame of your video. The resolution and aspect ratio together determine the picture size. The whole thing is particularly confusing because not all pixels are square.

It will be easier to understand if you consider an example like a DVD movie. Please keep in mind that decrypting movies from DVDs is illegal in the U.S.A., even if you own the disc. However, suppose your wedding video was shot by Francis Ford Coppola and burned on to an anamorphic wide screen DVD years ago. Now you want to convert that video to a DivX file.

On your television, the film may appear in a dramatic 2.35:1 aspect ratio with black borders on the top and bottom. Like most DVDs, you'd find resolution of the video file is 720x480 pixels. Since the film is anamorphic, your DVD player knows to stretch the video horizontally before you see it. So if the DVD knows that the pixels are supposed to be about 1.57 times wider than they are tall, the end result will be a widescreen picture with a 2.35:1 aspect ratio.

Unfortunately, it's not that simple. If you look at the video file on the DVD, you'd see that it claims the pixels are 1.18 times wider than they are tall. Then, you'll notice that there are 60 rows of black pixels across the top and bottom of every frame. Yes, it's crazy, but there are actually just 360 rows of pixels that make up each frame. Once the DVD player stretches the picture horizontally by 1.18 and you account for 120 rows of black pixels, you end up with frames that appear to be about 2.35:1 which is what Mr. Coppola had in mind all along.

Sadly, things are even more complicated than that. Not all videos will have borders exactly 60 pixel high. Some will be 55 on top and 65 on the bottom. Some will have 5 to 10 columns of black pixels on the sides. You just never know what you'll find.

The automatic cropping feature should make it easy to get rid of the borders, where ever they are. Just be careful with the resulting resolution. Dr. DivX only makes videos with square pixels so the aspect ratio will be defined by the resolution you choose. Most of the time, for 2.35:1 films, you'll want to crop the borders and resize the video to 720x304 pixels. High Definition Television is usually 16:9, so resize those videos to 720x400. Standard Television is 4:3, so 640x480 is a good size in that case.

Resize Filter

If you are resizing your videos, Dr. DivX gives you several resizing filters to choose from. It turns out that resizing a digital picture can be accomplished many different ways. For example, to cut a picture in half, you could just remove every other pixel. That's actually a rather crude technique and the results are very satisfying. What you'd rather do is take some kind of average between neighboring pixels and use that instead. Lots of mathematicians like Cornelius Lanczos spend countless hours trying to find a better way to resize pictures. Each algorithm has different tradeoffs between things like quality and encoding speed. You can try some experiments to find your favorite, or just settle for default option.

Advanced Codec

Codec Performance

The Codec tab under the Advanced tab is divided into three areas. They are Codec Performance, Rate Control, and Frame Control described in the following sub-sections.


Codec Performance

The options available for Codec Performance are the same as the Quality options on the Basic page. Flip back to the Quality section of the User Guide to jog your memory.

Rate Control Based on Bitrate

Rate Control

Adjusting the Rate Control setting begins with choosing a Mode. Would you like 1 pass or 2 passes? The answer may depend on how much time you have. The 1 pass option works just fine, but if you insist on getting the best possible picture quality, then tell the doctor to make 2 passes through your input file. That ensures that Dr. DivX doesn't miss any opportunity to optimize the picture quality but it also means the whole process will take about twice as long.

After you flip a coin to decide how many passes to make, you need to choose a maximum Bitrate. The higher the bitrate, the better the picture but it also makes for larger file sizes. You have to make the tradeoff. In practical use, video codec bitrates over 1300 kbps look clear even on big screen TVs. You'll certainly find them better looking than your average television broadcast anyway. If you are encoding files for small screens like PDAs or phones with only 320 pixels across, you may want to run the video down to 130 kbps. The result looks pretty decent on 3 inch displays and an hour of video is only slightly more than 100 Meg in size.

Rate Control Based on Quality

If quality is more important to you than file size, then try out the 1-pass quality-based mode. Using this option you get to pick a target quantizer. Sound nifty? The quantizer is just a number between 1 and 31. Opting for a lower number will give you better picture quality but you'll also get larger files. Larger numbers reduce the file size but give you worse quality.

In practice, a quantizer of 4 is good quality with reasonable file size. You may want to move it down to 3, but anything less than that won't make much visible difference for most people.

Frame Control

Frame Control Box

The Frame Control box will allow you tinker with key frames and rates. Each setting is explained in the following sub-sections.





Bidirectional

While many of the settings available under the Advanced Codec tab will simply affect picture quality, the Bidirectional setting can affect compatibility so this is an important one to consider.

Without going into too much detail about how video compression works, you should understand that the output file is basically a mixture of partial images with a few complete pictures sprinkled around (keyframes). DivX will start with a complete picture then progressively apply changes to make the picture move. Every once in a while, a new, complete picture is displayed and the process starts over again.

Turning the Bidirectional setting off, reduces the number of complete pictures that a DivX player has to track while displaying your video. Changing the setting to Adaptive Single Consecutive, makes DivX players remember more pictures at one time.

The catch is, not all players are capable enough to handle Adaptive Single Consecutive encoded videos. Particularly, small devices like phones may have trouble playing those videos. However, any devices that are DivX certified for the Portable profile or better, will be able to handle those videos with no problem.

You certainly want to use Adaptive Single Consecutive if your DivX player can handle it. Most can and it will provide significantly better picture quality in almost every case.

Max Keyframe Interval

Fundamentally, video compression is achieved by not including every frame from the original video. Only a few key frames are included in the compressed video. The DivX player creates the frames in between by incrementally applying the necessary differences. Dr. DivX tries to figure out the best place for keyframes and will try to go as long as possible without using keyframes. This gives the highest compression but it's also a lot of work for the DivX player. The Max Keyframe Interval allows you to limit how long Dr. DivX will go without a keyframe.

If you are experimenting with low-bitrate encoding, you may want to increase the Max Keyframe Interval to improve the over-all quality assuming your player can handle it.

Framerate

The Framerate setting controls how many frames per. second will be displayed while your video is playing. The exact numbers available for you to choose from will be dependent on the framerate of your original video, but you'll usually have two options that amount to full-rate or half-rate. Typically, you'll want the highest framerate possible. However, if you are making videos for small, portable, slow devices like PDAs or cell phones, you may want to drop the framerate to make sure that the player will be able to keep up. The result might not look as smooth but at least it will play.

Advanced Audio

Advanced Audio Tab

Each audio track can be encoding using different quality settings. For example, you may want the main audio to use a high bitrate for the best quality. At the same time, you could use a low bitrate for the director's commentary track to reduce the overall file size.

Select each track, one at a time, from the drop down list. Choose the encoding settings you want to use for the selected track. Most of the settings are fairly obvious although for MP3 files, you have a choice between CBR or ABR mode.

In Constant Bitrate (CBR) mode, the bitrate will be the same for the whole file. It means that each part of the audio will use the same number of bits. As a result, complex parts of the music will be of a lower quality than the easiest ones. The main advantage is that the final size won't change and can be accurately predicted.

In Average Bitrate (ABR) the encoder will maintain an average bitrate while using higher bitrates for the parts of your music that need more bits. The result will be of higher quality than CBR encoding but the average file size will remain predictable, so this mode is highly recommended over CBR. Unfortunately, not all players support ABR mode during playback.

Near the bottom of the Advanced Audio tab, there is a check box to encode all selected tracks with these settings. You may find this option handy if you are converting a video file with lots of tracks.

Batch

Since Dr. DivX can take so long to encode a file, the doctor likes to work in batches. Your video conversion jobs are queued up to be processed in the background so you are free to do important tasks like improving your Pacman score.

The following sections describe how to batch process videos.

Batch Jobs

Batch Jobs Window

The Jobs window on the Batch page contains a list of files; past, present and future that are queued up for conversion. Each line shows the name of the input file, the output file and the current status of the encoding. You can see more details if you hover over a line item with your mouse pointer which causes a window to pop-up displaying the full file paths and which profile is being used.

Along the bottom of the Jobs window, there are a series of buttons for manipulating items in the queue. The first will be labeled Stop or Resume depending on what the doctor is currently doing. You'll probably need to use the Resume button to start encoding the first video on the Job list although there is a setting under Preferences to automatically start encoding.

Moving to the right you'll find the Configure button. If you have second thoughts about what encoding options you want to use, you can highlight any item in the job list and press the Configure button to make some tweaks. Dr. DivX will the job back to the File page where you can readjust the encoding parameters before pressing the Encode button to put the file back on the Batch page.

Of course there's a Remove button in the middle that obliterates jobs from the batch. Just highlight the item you want gone and press Remove. Be careful though. Dr. DivX will drop the job straight away without the customary, are you sure? warning.

The last two buttons are to reshuffle videos in the queue. Dr. DivX will work through the list sequentially from the top. If you care about which files get converted first, you can use the Move Up and Move Down buttons to change the sequence.

Batch Plugins

Optional Plugins

If you are really into encoding videos in batches, you might like to tinker with even more tools to automate processing your files. The Batch Plugins feature gives you lots of flexibility. Plugins are automatically executed as each job from the batch list is completed. There are a variety of plugins to choose from. For example, you can have your encoded videos automatically uploaded to a remote FTP server or simply ask the doctor play a sound when each job is done. There is even a plugin that lets you run any other application you'd like.

New plugins can be added to Dr. DivX by placing the new plugin DLL file into the Plugins directory. Someday there might be a Dr. DivX Developer's Guide that explains how to make new plugins. For now, you are on your own.

Add a Plugin

Adding a Plugin

To add a plugin to one of the jobs in the batch list, highlight the job, and then click on the Add button under the Plugins box. You'll see a list of plugins to choose from in the Plugin Selection window. Click on the name of the plugin you want to use, fill in any options that are required, and then click on the Add button.

You can specify multiple plugins for each job and each job can have its own unique combination of plugins. When the job is complete, Dr. DivX will invoke the plugins you requested.





Remove a Plugin

If you decide you don't want a plugin, highlight a job in the batch list, highlight the name of the plugin you want to remove, and then click on the Remove button.

Batch Running Jobs Status

Job Status Example

The Jobs Status box will keep you apprised of the doctor's progress while encoding your videos. Highlight a job in the batch list and the status box will indicate if the job is waiting to start, currently in progress, or completed. While the encoding is in progress, Dr. DivX will show some entertaining graphs parading by to assure you that real work is being done. When a job is complete, there will be two buttons in the Job Status box that will help you find your newly encoded video or start playing the video for your review.


Thread Priority

If it weren't for Thread Priority, using Dr. DivX would be unbearable. By default, the priority is set to Low. You probably want to leave it there. Encoding videos can take a long time. Actually, it can take a really long time. Using the highest quality settings, a full-length movie may take 15 hours to encode on an older PC. If you don't have a computer to dedicate to the task, you probably want to be able to do a few other things while your videos are being processed.

Setting the priority to Low means that the doctor's work takes a back seat to your work. You can go right ahead surfing the net or writing your term paper. Your computer won't feel much slower than it ever does. Dr. DivX will only work when your computer is idle. That's actually more often than you might imagine. While you are reading a page or trying to decide what to type next, your computer isn't doing much of anything. Dr. DivX uses that time to get some video encoding done.

The beauty of the arrangement is, if you are in a hurry for your video; just take your hands off the keyboard. The doctor should cruise along at top speed as long as your computer isn't trying to do anything else. That's why there are few reasons to bump the priority up to anything above Low. Your computer can't go faster than 100% and as long as you aren't using anything else, Dr. DivX will work just as fast on Low priority as on High priority. Although, for the best speed, you might want to turn off any screen savers you normally use.

Preferences

Dr. DivX has enough bed-side manners to listen to what you like. There are several pages of preferences for you to pick from that control what the doctor decides to do by default. The following sub-sections will tell you all about the preferences.

General Preferences

General Preferences



When designers have a bunch of settings that they don't know what to do with, they create a General Preferences page. On this screen you'll find a bunch of miscellaneous stuff that doesn't necessarily go together but it's all important, nonetheless.












Start Encoding on Startup

Dr. DivX keeps a waiting room of encoding jobs in the batch queue even when the doctor is not running. You can exit Dr. DivX, restart it, and you'll find your files are still waiting in the queue.

Normally, the files just wait in the queue for you to manually kick off the encoding. However, if you check the Start Encoding on Startup option, Dr. DivX will automatically resume working on the queue as soon as the program starts.

Check for Updates

Dr. DivX may be good, but there's always room for improvements and there is a dedicated team working 'round the clock to make the doctor a more capable physician. By ticking the Check for Updates option, you will allow Dr. DivX to quietly and periodically ask the Dr. DivX website if a newer version of the doctor is available. If an improved doctor is waiting in the wings, Dr. DivX will prompt you to upgrade.

Dr. DivX will use the Internet to look for new versions of Dr. DivX, but only if the Check for Updates option has been selected.

Remove Working Folder

Sometimes Dr. DivX doesn't get to finish operating. There are a few different reasons why an operation may fail, but when it does, the doctor may leave some files behind in the temporary directory. If the Remove Working Folder option is checked, the doctor makes sure those temporary files are tossed out so they don't languish, wasting space. If you aren't a software developer and have no desire to become one, you probably want to check this option. The only reason to keep such files is for postmortem studies.

Dr. DivX will delete all working files in the temporary directory if a failure occurs and the Remove Working Folder option is checked.

Encode All Files To...

When Dr. DivX gives birth to a fledgling DivX video file, the newborn is gently deposited into the directory specified under Encode all files to. This is a setting you probably change. By default the target directory is well hidden. You may prefer to specify a custom location such as your DivX movie directory or your My Videos directory. You can also choose the Input Directory option if you want to keep the newborns with their parents.

Dr. DivX uses the Encode all files to Custom Location directory to store all newly encoded files. If the Input Directory option is selected, Dr. DivX will store each encoded file in the same directory as the input file that was used to create the DivX encoded file.

Plug-in Folder

No doctor works alone so Dr. DivX keeps a staff of helpers in the Plug-in Folder. If you think you know best, and you'd like to tell the doctor what to do, then write your own plug-in and plop it into the Plug-in Folder. This User Guide won't explain how to write a plug-in. You'll need to find a Developer Guide for that.

Dr. DivX looks in the Plug-in Folder directory for dynamic link library (DLL) files that extend the available features and functions.

Profiles Folder

Dr. DivX has a repertoire of standard DivX Certified Profiles for encoding files. Don't go looking for those profiles in the Profiles Folder directory. They aren't there. However, you can create custom profiles and those will indeed land in the Profiles Folder.

Dr. DivX uses the Plug-in Folder directory to store XML files which define the custom profiles of encoding settings.

Log Files

Since most doctors have horrible handwriting, Dr. DivX neatly types notes and stashes them in the Log Files directory. If something unexpected occurs while the doctor is working, you may find a few clues in the log files. Unfortunately, even though the logs are neatly typed, they mostly read like gibberish to the untrained eye.

Nonetheless, while Dr. DivX is encoding files, detailed progress reports are written to plain text files and stored in the directory designated for Log Files. Log files generally aren't more than a few hundred kilobytes but a string of errors can cause log files that are several megabytes.

Temp Directory

The doctor keeps doodads in a temporary directory. Don't get too excited about any of the treasures you find in the trash. There probably isn't anything useful in there. It's also unlikely that you need to change this directory. However, if you have multiple drives and you want to spread the trash around, the doctor lets you specify any temporary space you'd like.

While Dr. DivX is encoding files, some intermediate results are stored in the directory designated as the Temp Directory. Make sure there is plenty of space available in the temporary directory.

Language

Dr. DivX is full of buttons, menus and checkboxes. They all have labels. The Language option allows you to choose the dialect used by the doctor to speak to you. There are at least a dozen language options available and more will be added as new translations are completed. If you can translate the doctor's lingo to another language, step up and volunteer for the open source project. Anyone speak Klingon?

To change the language, select your preference using the drop down list, press the OK button, and then exit Dr. DivX. The next time you start the program; all the labels will appear in the language of your choice.

Audio-Video Options

Audio-Video Options




Under the Audio-Video Options tab, you'll discover settings that have a lot more to do with video encoding quality than anything related to audio. If you aren't too disappointed, then read the next couple sections to learn more.












Audio-Video Default Output

When you start up Dr. DivX, a couple default settings take affect. For example, the Home Theater profile is selected and the quality is Balanced. If you are tired of always switching those to Handheld/Fastest or High Definition/Insane, then trod on over to the Audio-Video Default Output settings and choose the configuration you use the most. You can even choose from one of your custom profiles or limit the size of the output file. The next time the doctor begins to work; your choices will be the default settings.

Audio-Video Resolution

There is a warning next to the Resolution settings that attempts to scare you away from messing with them. You are probably wise to heed the warning and just leave the width and height settings at 16.

Maybe you are a scofflaw, bent on experimenting with everything. In that case, you should know that DivX (like most video compression algorithms) works its magic by dividing frames into macro blocks and then tracking the movements of those blocks from one frame to the next. The algorithm is optimized to deal with 16 by 16 pixel macro blocks. Theoretically, if you had a lot of small moving elements in a scene, you may get better quality compression by reducing the size of the blocks. For example, rain is always a difficult effect to encode well. There are lots of tiny blobs, all moving at high speed. Such a scene may benefit from using smaller macro blocks but in practice you are best advised to leave the resolution settings alone.

Watch Folders

Watch Folders

Do you have a whole slew of files in a directory that need to be converted? Every time you plug in your digital camera does it automatically copy new movies to your computer? If so, you may find the Watch Folders feature very handy.

You can ask Dr. DivX to keep an eye on particular folders. If any new video files appear in that folder, the doctor will automatically queue them up for conversion.

To test it out, go to the Watch Folders tab in Preferences. Click on the + button to add a new folder. Dr. DivX will prompt you for a name, it doesn't matter what you choose, just make it something meaningful to you. Next, choose an input folder like My Videos. Then pick an encoding profile and quality setting. Finally, specify an output folder like DivX Movies.

On the left hand side, Dr. DivX will display a list of all the watch folders you created. You can individually activate or deactivate folders using the check box next to each folder name. The - button will delete folders. Make sure the folder you just added is checked then put a couple new video files into your watch folder and prepare to be amazed. The next time you look at the Batch page in Dr. DivX, you'll find all your new videos queued up, ready to be converted using your settings and then stored in your output folder.

The detailed descriptions of how Watch Folders work is rather complex. Much of it you'll figure out on your own, but you may notice some surprising things. For example, deleting a file from a watch folder will not remove it from the queue. It will just cause Dr. DivX to complain when the conversion starts. The doctor will mark it Failed and move on.

The filename and extension don't mean much to Dr. DivX. The doctor will test every file in the directory to determine what is a video file and what isn't. It doesn't matter if you put .avi or .txt on the end, Dr. DivX will find the videos and convert them.

Dr. DivX constantly monitors for new files to be added. If the doctor is running when you drop a new file into a watch folder, that file will immediately be added to the queue. If Dr. DivX is not running, it will catch the new addition the next time around.

Watch Folders can be very handy for automating conversions. For example, make a directory called For-Palmpilot and set it up as a watch folder using the Handheld profile. Then make a directory called For-Television and make it a Home Theater watch folder. Now when you want to convert a file for you TV, drop it into the For-Television folder. On the other hand, if you want to take the video with you, place it For-Palmpilot. Dr. DivX will automatically queue those files up for conversion using the correct profile and save you a lot of repetitive mouse clicks.

About

Amazing revelations await you under the About tab. Stare at it wondrously. The hunger pains are usually followed by visions of trippy stuff. You have now attained enlightenment.