The 'Unofficial' iMovie FAQ

Working with DivX and AVI files

Last edited:7 December, 2004
Author: Daniel Slagle

This site is NO LONGER being maintained for the "ALL NEW" site that talks about the new iMovie 11 please visit

Note: If you have a specific question on DivX or AVI files PLEASE do not e-mail me.  I do not personally use DivX or AVI file unless I have to.  If you have a specific question please visit the DivX or 3ivx forums.

  1. What is an AVI file?
  2. What is the easiest way to play them on my Mac?
  3. Are all AVI files DivX?
  4. What are the other ways of playing DivX files?
  5. What is 'doctoring' an AVI file and do I need to do it?
  6. What does the divX Doctor do to an AVI file?
  7. What Additional Codecs can I use or will I need?
  8. Why is there no sound on the DivX file I made from a QT movie using ffMpegX?

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What is an AVI file?

AVI is not a true file "format" it is a "container format". Inside the file can be about anything, meaning it can contain video audio compressed using many different combinations of codecs. So while MP3 and JPG can only contain a certain kind of compression (MPEG Audio Layer 3 and JPEG), AVI can contain many different kinds of compression (eg. DivX video + WMA audio or Indeo video + PCM audio), as long as a codec is available for encoding/decoding. AVI all look the same on the "outside", but on the "inside", they may be completely different. Almost all tools on this site are not just DivX tools, but also AVI tools, so will probably work with other codecs.

There is no such thing as a "normal" AVI file, but the closest you can get is probably an AVI file that contains no compression. AVI files has been around since the time of Windows 3.1, so by no means is it a new thing, and is probably the most common video format around (although its popularity wavered a few years ago, but has since come back with a vengeance due to the emergence of DivX). AVI files may also have limits under Windows 95/98, and for more information, please read this article. Note that AVI files without file limits (other than the Windows Fat32 file limit) are usually referred to as OpenDML AVI files.

More information can be read here.

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What is the easiest way to play AVI files on my Mac?

The first time you encounter an .AVI, QuickTime may open the file, but all you see is a blank or sickly green screen, no audio, and an error message. This means that you lack the necessary codecs/decoders for proper playback.

Almost all files you will encounter have a video track in some flavor of DivX with an audio track encoded as VBR mp3, or lately, ac3. While QT can play an .AVI with a CBR mp3 audio track, a VBR-encoded track will play with a great deal of stuttering or drop out completely after a few seconds.

Some older files may have been encoded with MP42 or MP43, two of Microsoft's earlier entries into the mpeg-4 field. Decoders available here (missing link).

Still older files may have been encoded with one of the Indeo codecs, none of which have been ported to OS X. If you wish to view such a file, download the full set of Indeo codecs and install in QT in OS 8/9.  Regarding Indeo compression, there is a QT decoder for Indeo 263 (I263) that has worked for me in OS 9 and lower. The author says he doesn't know if it works in OS X and I have not tried it there either, but here is the link for the decoder.

Here are the most common solutions:

  1. Use an alternative player, such as VideoLAN Client (aka VLC) or MPlayer, both UNIX players now ported to OS X. If a file does not play properly in one of these players, then your chances are slim of ever getting the file to play on a Mac.
  2. Download DivX Doctor II, the 3ivx codec, and the .wma decoder and install as directed. Use DivX Doctor to convert the .AVI into a .MOV. Note: DivX Doctor is extremely intolerant of errors and sometimes creates a .mov file with bad synchronization.
  3. Purchase the trial or pro version of the DivX 5 package, which contains an MP3 decoder for AVI's to play natively in QT. The free version does not contain the MP3 encoder and allows you only to encode a DivX video track in a .MOV

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Are all AVI files DivX?

No, although 95% or more are today, due to the fact it is used in the popular (and PC-centric) peer-to-peer groups.

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What are other ways of playing DivX files?

  1. Using VLC
  2. Using Mplayer
  3. Using DivX's codec from within Quicktime
  4. Using 3ivx's codec-- requires converting unless paired with DivX's codec; but some say it gives higher playback quality then the DivX codec
  5. Use the open source ffmpeg DivX codec

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What is 'doctoring' an AVI file, and do I need to do it?

Quicktime adheres to the AVI standard. The problem is that AVI files with VBR MP3 audio tracks are not supported (it's a hack to the AVI format), so you get no sound or very stuttering sound when you try to play it. DivX Doctor works by correcting the audio information and sticking it in a Quicktime movie file with the video.

Why might you still want to do this after DivX's AVI Importer came out?

  1. Streamable
  2. As many audio/video/text/flash tracks as you want
  3. Metadata
  4. Chapter tracks
  5. A, relatively, open format that is ludicrously easy to edit and convert
  6. Ability to create interactive menus using sprites

Grabbed from the 3ivx forums.

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What does DivX Doctor do to an AVI file?

DivX Doctor II first extracts the audio track, then the video, then, in QuickTime Pro terms, adds, rather than adds-scaled, the video to the audio. If you save as a dependent file, the Doctor creates a .MOV with the entire audio track but with a link to the video of the original .AVI

If the "flattening" process takes too long or hangs indefinitely, try saving as dependent, then opening this file with QT Pro and saving again as self-contained movie.

Sometimes the Doctor produces bad synchronization

Solution 1: Open the .mov file the Doctor has produced. Extract both tracks, and add-scaled the video to the audio. Save as self-contained.

Solution 2: If the synchronization is still off, but consistently so, use QTMutator.  For more serious problems, use SyncHole.

I get an error message in DivX Doctor, "Audio may be truncated", but the file plays fine in VLC. Can I fix this movie?

You can extract the audio track yourself using DivX Tool(link) or the pass-through option of ffmpegX (see below). Then in QuickTime Pro, follow the steps outlined above in Solution 1.

DivX Doctor refuses to convert an .avi, it won't open in QuickTime, but it plays in vlc. How can I view this movie in QT?

The file may have been mislabeled, in which case, it could be anything (.RM, .ASF, WMA, MPG (MPEG), etc.). Try the info feature of DivX Tool or ffmpegX. If all else fails, open the file with a Hex Editor. If it is an .AVI, then the header will begin with RIFF.

If you see the progress arrow in VLC move slowly to the right before playback, this means that the index of the AVI is corrupted or faulty. While VLC can reindex on the fly, QT requires this information intact.

The index is a footer at the end of the file and contains timing information necessary for playback. A .mov has a much smaller header, which is why a doctored .avi>.mov file is always smaller in size than the original.

You can reindex an .AVI in several ways;

  1. Use the "fix" option in DivX Tool.
  2. Use pass-through options on both audio and video tracks in ffmpegX, then discard the original.
  3. If you have installed ffmpegX or any other GUI to MEncoder, then you can use the terminal:Open the Terminal app and after log-on, type:
  4. mencoder -idx yourinputfile.avi -ovc copy -oac copy -o youroutputfile.avi
  5. Hit return.
  6. You can drag the original .AVI to the terminal window after typing "-idx", then again for the output, making sure you change the name for the new file.

Can I share a doctored .MOV with someone with a PC?

Yes, but they must install 3ivx for Windows. This will enable them to view your doctored file in any DirectShow application.

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What additional codecs can I use or will I need?

There are MP41 and MP42 codecs available for OS X

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Why is there no sound on the DivX file I made from a QT movie using ffMpegX?

I am trying to make a DivX version of the QT movie I have edited iniMovie. I exported the movie as full sized version but after encoding I have no sound when played in Mplayer.

If you are using QT as your player, you will have to "Doctor" the file. See XXXX. Mplayer or VLC player offer you playback in OSX with out this procedure. If your problem persists, read below.

When setting up your encoding from a Quicktime movie, you have a choice of audio tracks. The default is track 1. However, Quicktime sometimes uses track2. So if you have no sound, select track 2 and try a 5 second encoding session to so if that fixes the problem.

Other problems can arise if you select the wrong audio setting for the sound option under the QT export. Make sure it is Stereo, and 44 or 48Khz.

Note: when making a VCD file using ffMpegX, it is not an issue.

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