avi to movs, sort of

[elmimmo]

This thead tries to somehow answer the question of how to better view normally unviewable avis in a Mac, asked by... er... someone at this other thread, where it happened to be quite offtopic.

I guess your main concern is with so called DivX avis. First you have to understand that both Windows Media' avis and QuickTime's movs cannot be considered a format in the way you consider an image to be in gif or jpeg format. They would be more appropiately called software platforms or wrappers, since they are simply an envelope in which to hold different kind of media (video, audio, static image, flash, text, hyperlinkable areas...). But simply because of the way it turned out, people kept calling Quicktime and WindowsMedia "formats" (well, Windows' platform never had a distinct trademark until recently AFAIK) and the compressor used to shrink the video or audio "codecs", which stands for compressor-decompressor, and is what in reality would resemble what in a still picture is gif or jpeg as its format (or compressor in fact).

An application which communicates with Quicktime can use all Quicktime compatible codecs installed in the machine that the user is using, and if that application communicates with Windows Media it can use all Windows Media compatible codecs installed too. Take into account that you can stuff, say, an mp3 song into either an avi and a mov, so in essence both files would be the same format internally, but since they use different wrappers only a Windows Media engine would be able to read the mp3 inside the avi and only a Quicktime engine would be able to read the mp3 inside the mov, and not vice versa, since both engines need their own particular codec to decode the mp3. That means, unfortunately, that each one's codec is not interchangeable (Quicktime's engine cannot use Windows Media Player's windowsmediavideo8 codec -microsoft latest video codec-). This also means that having a Quicktime engine does not guarantee that you will be able to read whatever mov, since your Quicktime engine also needs a certain codec to read a certain file. This is why certain movs require that you have a certain version of Quicktime installed, since the codec needed to read the file is only included with the standard installation of that version.

Somewhat fortunate for us Apple included in QuicktimePlayer both a Quicktime engine (of course) and a limited Windows Media engine. But as I said having the engine does not solve all our problems, since you need yet a particular codec for a particular file. Unfortunately the WM codecs included with QT are quite old and nowadays useless. Besides commercial codecs such as Windows Media Video 8 being developed as time passes and becoming somewhat standard in high quality WM sources in the internet, the same as we have Sorenson 3 which requires QT5, the Windows population is so enormously bigger compared to that of the Mac OS, that the percentage of "techno-geeks" (I am not saying this term with any offensive intentions, I hope nobody is offended) trying to go beyond standards burocracies and developing their own higher quality codecs turns into an absolute number much much bigger in the Windows platform than on the Mac OS.

Have you heard about all the fuss about Quicktime 6 and its "innovative" incorporation of MPEG-4. Well, as with most of things lately, rogue techno-geeks are well beyond us the mortals and have been developing powerful and easy to use MPEG-4 encoders and decoders since a long time ago, avoiding license and pattents possible problems, and also, as expected, evolving tools based on unfinished standards which happen to later, sometimes, grow old not so healthy not complying later with agreed standards they tried to pioneer. And of course, this mostly happened in the Windows platform because of the simple reason that most of this "techno-geeks", out of probability, where Windows users. (Ok, this is not completely fair, QT6 does come with an innotive use of MPEG-4 which is its ability to play MPEG-4 broadcasts, which is a somewhat special and different technology than the one needed to play an already downloaded movie)

That's what DivX at the end is: MPEG-4 video in an avi wrapper. It is really only legacy and standard compliant MPEG-4 video in tracks encoded with DivX enconder v4 and on (they are currently on 5). DivX 3, identified by Quicktime as MPEG4v3 in the info window, is not standard compliant MPEG-4, and sure you could argue that they could have just waited for the standards to be more finished, but in the meantime they enjoyed a codec which represented quite a breakthrough in compression-quality ratios compared to what could be normally found at the time (first I saw it is 2 years ago) and we did not. It drove us Apple users nuts simply because, being it a rogue codec, there was no worthy Mac representation of research behind the same goal backed up by the money of a commercial firm (and thus having people on it 8h a day and compensate for the disadvantage). There are however open hearted techno-geeks on the Mac scene too, just not as many, so quite quite later than in Windows we had our own MPEG-4 decoders without the need to wait for the one included with Q6. The one I have tried which works like a pleasure is the 3ivX codec. It was originally another sideMPEG-4 similar but different from DivX AFAIK. The v4alpha version, which currently only decodes can read standard MPEG-4s encoded with whatever other encoder (DivX>3 or Q6) and even non-standard DivX 3. Get it at 3ivX.com.

 

[elmimmo]

But that is only part of the cake. I have been only talking about video, and its codecs. Audio, unfortunately for Apple users, also caused and is still causing quite some headaches. Mostly you will find two different kind of sound compressors used in movies where their video is DivX. One is MP3, either constant bit rate or variable bit rate (although AFAIK VBR is out of the avi standards, but again, this usually are rogue movies made with rogue tools -which does not necessarily imply its illegallity: lots of people use those tools nowadays to compress their own creations). The other is Windows Media Audio. Both represent a headache for Mac OS users.

The first one because, although Quicktime's Windows Media engine can decode MP3, it is badly made and cannot play an MP3 track along a video track keeping both synchronized which it other. Many people have reported this to Apple, and are awaiting QT6's way of dealing with this, but the latests previews of it show Apple has not solved the problem yet. The solution that I've seen used most is simply copying the MP3 track into a Quicktime movie (since both Quicktime's and WM's engines can decode this data you can swap from one to the other without any recompression), and try to play the MPEG-4 track in the avi through Quicktime's MPEG-4 decoder (in my case I use 3ivX 4a). It is not the most comfortable solution since you end up with 2 files instead of just 1 and the total filesize grows about 10% (since you have the audio both in the original avi movie even if you are not playing it, and in the mov, which is the one you are playing to avoid using Quicktime's avi handler). You could build a selfcontained mov with a MPEG-4 video track and a MP3 audio track, but then the only way to play that movie back in a Windows would be through Quicktime for Windows (which, in Windows, consumes more resources than WM does) and with the need to install a MPEG-4 video decoder for Quicktime for Windows too. 3ivX builds one too, I think, but it is absolutely much much more uncommon than the original DivX decoder dor WM. You make this second mov with DivX Doctor II which you will be able to find to at 3ivX.com

The other one, Windows Media Audio, is simply too new for Quicktime in the Mac OS to recognize it (although Microsoft is to blame for that, since wma not being open sourced or at least open to Apple, Apple cannot do anything to implement it on QT's WM engine -the same can be said, though, about Apple and its take on the innability of Windows Media Player for Windows to play quicktime movies, which once it did, so no one's better or worse than the other in reality, just two parties trying to push their standards and block the other's). There is no way that I know of to play Windows Media Audio with Quicktime (which is what you'll use to play the avi). The same folks at 3ivX, with the aid of DivX Doctor II and a wma extension (which you can download at the same place as the doctor), can help you uncompress the audio in a wma track inside an avi, although not in real time. It will create a 44kHz 16 bit stereo uncompressed sound track inside a new mov out of the original wma. It is quite a pity they did not include the ability to recompress the wma to another format, since an uncompress audio track of a fullfeature movie can weight as much as 1GB (and remember you still need the original avi for the video). I guess it would be wise to recompress manually that audio. I have not done that, but if you are in the need tell me, it must be quite easy to get the same final output as the MP3 case.

So what to do? Simply download the 3ivX v4a codec, the DivX Doctor II and the wma extension, and install them. Restart. Try to open the file: if the screen i still blank probably the video is not DivX but another format; if it plays fine there you got it; if it plays but audio is out of synch, drop it into the Doctor (without making a self-contained moive -which means undependant of the original avi, just in case you want to save it to play it on a PC), and you'll be returned a mov with good synchro; it it plays but no audio is heard, drop it into the Doctor and you'll be returned an huge mov with uncompressed sound which will still be dependant of the original, which will play now ok, but you can compress the audio for better storage (step by step if there's interest)

There are other WM codecs around, each of one will require one thing or another, or will be simply impossible to be played, since not even the latest Windows Media Player for Mac OS includes all the default codecs that the latest Windows Media Player for Windows includes (and this time Microsoft is indeed to blame for that). The are for example some quicktime extensions to read video in Indeo format (an Intel's codec), but I have no clue where to download it (have not tried). Other formats you will be simply better off playing them in WMP such as one other WindowsMedia video format with extension .asx or .wmv (which, again, will be playable or not depending on which codec are the internals compressed with). The only exception to this are files with the extension .divx, they should be really named .avi, but creators renamed them to clearly identify that the video inside the avi is an MPEG-4 encoded with DivX.

Phew, that all at least for the moment. Yet I am just a user, no expert, so I might have put my leg into a nasty hole more than once in the text saying things that are not quite true. Anyone's collaboration will be appreciated.