DivX is the name of a specific video compression codec (compression-decompression) developed by DivX, Inc. The format was developed to enable users to create very high quality video with very small files sizes.

The DivX codec is currently the most popular MPEG-4 based codec because of its quality, speed and efficiency. As is usually the case the popular becomes more popular because… well… it’s popular! So as a result most modern DVD players and devices are now compatible with the DivX standard.

DivX is based on the H.264 standard which in itself is an MPEG4 variant. It is important to note that terms like MPEG2 and MPEG4 are not codecs in themselves although the terms are used in this context quite often. Both MPEG2 and MPEG4 are a set of rules or standards that dictate the manner in which particular video files are encoded and rendered (played back).

What is H.264?

To be blunt H.264 is probably the future. It is most likely that the current MPEG2 for DVD and DV avi video files types for camcorders will be phased out in favor of H.264 or something similar.

H.264 provides very powerful compression technology that delivers superior video at a low bit rate. It can run across many different types of platform and is suited to high definition production.

The H.264 standard reduces the amount of information required to reproduce a video…

How?

The H.264 encoder is able to divide each picture recorded into a set of blocks, it then searches the pictures in the video stream before and after the picture being encoded. It detects the changes between the before and after pictures as compared to the current picture and carries out what is called “motion estimation.” That’s just a fancy was of saying it makes a calculated guess as to what the changes are.

H.264 inspects the before and after pictures down to the level of one quarter of a pixel pixel for this motion search resulting in quite amazing quality.

Once it has done that it now “knows” what is the same and what is different and simply put, it throws out everything that is the same and only keeps what is different.

When the file is played back the decoder in the playback device will hit the picture in the example above. It will display a little of the total picture from the information in the file but mainly it will go to other pictures (before and after the current one) to find the rest of the information it needs to show the complete picture.

That is how it manages to achieve such small video file sizes.

It is a common misconception that H.264 is a format with only a single form. Not true. Mov files are H.264 and very often you will find that files you see that are marked as MPEG4 are actually H.264. H.264 can occur under a number of guises displaying a wide range of parameters.

For a complete look at this style of compression you can take a look at this post here under MPEG2 and MPEG4 Editing software or here for Video File Formats Explained.

As a video file encoding format H.264 represents probably the best quality for file size trade off on the market today and the DivX implementation of H.264 represents the best of the best.

The Downside

Like all highly compressed video file formats DivX was not designed in any way as an editing format. It is what is called a distribution format and is intended as the video file format to be used in the final product. Editing DivX files can be a nightmare and the reasons for this are explained in the links above in this post.

Compatibility with Other Video Editing Software

Because DivX is a specific codec it is easily implemented into your existing video editing software. All you have to do is download the codec from www.DivX.com and install. From that point forward when you choose to render a final video file of a project DivX will appear as one of the choices for file output.

Each type of video editing software will have a slighly different place in which you will gain access to imported codecs so just check your particular software documentation for details.

Well it’s good news and bad news today so lets start with the good news.

DivX announced that they have finally released a version of their excellent DivX Pro encoding software for Mac users. DivX is probably one of the best compression codecs on the market today providing amazing quality from tiny file sizes.

Here’s how they have cheerfully presented it:

“Spring is here and in full swing and with it, we have launched our newest product offering, DivX 7 for Mac. With HD Playback, Gesture Controls, superior AAC, and Support for DivX video creation, DivX 7 for Mac has everything you need to create and play high quality DivX videos.”

And now news from the dark side:

Corel Announces Workforce Reductions

Corel have announced a reduction worldwide in their workforce citing the current economic downturn as the reason why.

Personally I think that’s bollocks (rubbish for those of you unfamiliar with the term bollocks!).

In their annual report to investors last year they blamed many of their products “reaching the end of their life cycle” as a cause for their financial woes. I think more to the point they have failed utterly to develop their products in response to consumer needs to keep them fresh and marketable.

Speaking of marketing… well they just don’t really.

I am sure the takeover of Intervideo last year was a move by Corel to get a hold of some fresh product via the Ulead range of video editing tools and software but then they promptly dumped Media Studio Pro and Cool 3D which were two wonderful programs.

Since then they have been picking over the carcass of Media Studio Pro and incorporating the the pieces into VideoStudio resulting in VideoStudio Pro X2 but unless they get the concept of product development through their heads they will fade from view there as well.

In its current incarnation VideoStudio Pro X2 can hold its own amongst the likes of Cyberlink Power Director, Adobe Premier Elements and Pinnacle Studio et al but this is a competitive market of the quick and the dead. Compare Corel’s sluggish motion on a number of fronts with the all out “balls to the wall” attitude of Magix at the moment.

Magix have come out with all guns blazing with a very, very good consumer level video editing suite in Magix Movie Edit Pro 15 as well as a top end “prosumer” suite called Video Pro X which is clearly aimed at the serious enthusiast.

As an example of Corel’s slow descent into unconsciousness let’s take a look at their “user to user” forums. The old Ulead forum was a hive of activity back in the day but since Corel have taken over it has become a graveyard by comparison. Over 9 months ago problems with the software the board was running on were being reported… and reported… and reported with Corel all the while sitting on their corporate hands doing nothing.

It is hard to comprehend an act of greater business stupidity than to allow one of the most powerful selling points of your premier software to sink slowly into the swamp for the sake of a server upgrade and a $100 software update! Yet that seems to be the case here.

Time will tell as to whether Corel can get their act together or whether VideoStudio goes the way of a few other good programs that fell into their clutches!

When it comes to video editing software a common complaint I see on the video editing forums is that the software wont do what it says it will do!

Almost invariably the person making the complaint reveals by their question and subsequent conversation a basic lack of understanding about what they are doing and how the video editing software really works.

Of course in an ideal world you should be able to just point and click your way to cinematic success…just like the product marketing says… right? Wrong! The problem is we don’t live in an ideal world

In the past complaints were generally confined to problems that were being generated by computers struggling to handle the large amounts of data and the huge file sizes generated by the existing video file formats.

Many of those problems were relatively easily solved by advice that even today stands true. Turn off background programs, defrag your hard drive etc., all the things that would release computer resources back to the video editing program.

However the introduction of MPEG2 video, then MPEG4, H.264, and a slew of other very highly compressed formats has resulted in a huge increase in complaints about video editing software not doing the job. When you add in the complexity of the high definition versions of these video file formats, HDV and AVCHD then the excrement really has hit the rotary oscillator!

So, I am about to attempt the impossible in an effort to help you understand what is at the heart of this problem. This is really technical stuff and I am going to try to keep it real simple. For the technically superior amongst you please forgive me if my simplification offends you!

If you are a sucker for punishment there is even more to read here on video file formats explained.

To assist you even more I have attached two “post it” notes to the top of my computer screen. One says, “Keep it simple!” and the other says, “Stop rambling you fool!” Hopefully I will refer to these often and spare you from sinking into unconsciousness. So here we go!

The basic problem is this. The modern batch of highly compressed video file formats were exclusively designed for playback or distribution… not editing. It is as simple as that.

If those video file formats had been designed with editing in mind then right now hundreds of video editing software programmers would not be collectively jumping through hoops trying to nail down the definitive method of editing them.

It gets worse.

These new video file formats are not a strict set of rules and regulations that result in a very narrow set of parameters. They are very broad in their description an implementation. If you want an example take a look here at What is DVD? and you will see that within the “DVD Standard” alone there is a huge variation in what can be called DVD. Well, that’s just standard definition MPEG2 really but it will give you an idea.

For the programmers that means trying to create a video editing program that edits MPEG2′s (for example) BUT the question is what flavor of MPEG2…which one? The same applies to MPEG4 and others and is further complicated when we move to high definition video file formats.

And it gets worse…

The common modern video file formats you will encounter could essentially be described as derivatives of either MPEG2 and MPEG4. It doesn’t matter whether they are high definition or not they have the same inherent problem for video editors although high definition makes the existing problem worse.

These video file formats are all basically made in a similar fashion and achieve their very high compression rates by throwing away information. The word “compression” in a bit more marketing than reality! They rely on a system of throwing away data that is unnecessarily repeated in frame after frame of your video. The data is replaced by a reference to an earlier or later frame rather than the data itself.

(Note to self read keep it simple note)

So I am assuming you know that video consists of a series of pictures that are displayed one after the other at a set rate between 24 to 30 frames per second and from this you get the sense of motion… right?

In these modern video files there are three types of picture and this is how the compression is acheived.

I-Pictures.
These are easiest to think of as a complete picture. They are slightly compressed like a JPEG photo file is compressed but they are as close to complete as you will get.

P-Pictures.
These are incomplete pictures and only contain the infomation that has changed since the last I-Picture or the last P-Picture.

Imagine a bird flying though the air against a bue sky. The I-Picture is a record of the whole picture. The P-Picture is a picture of the bird in a changed postion only. To display the rest of the picture on the screen (the blue sky which has not changed) the P-Picture tells the playback software to go get the data from the previous I-Picture or P-Picture.

In the older video file types such as MPEG-2, P-Pictures can use only one previously decoded picture as a reference during playback. In MPEG4 or H.264 the P-Picture can use a number of previously decoded pictures as a reference during playback and this is one way greater compression is achieved retaining quality.

B-Pictures.
These ones are the most highly compressed because they can use information from previous I- or P-Pictures and forward I- or P-Pictures for reference in playback. This is a huge advantage over MPEG2 in calculating motion and so retaining smoothness in a much smaller file size.

This also explains the huge demands that are placed on any computer trying to edit or playback AVCHD video files. The B-Pictures are demanding the software retrieve the majority of the information from Pictures that have already passed or that are yet to be played.

So what the hell does that all mean!

Actually I am not finished yet.

These I, P, and B Pictures are arranged in a way so that the video file can be played back by software from a DVD drive, PS2, computer player or… whatever! The Pictures are arranged into groups that will allow the best playback quality.

These are called Groups Of Pictures… unbelievable they came up with that!

It would be too easy to call groups of pictures… Groups of Pictures right?… too self explanetary! So they are called GOPs. Why? Because geeky computer guys like that sort of thing and there is already a U.S. political party called the GOP so the possibility of confusion is ideal.

There are generally two types of GOP, Short GOPs and Long GOPS, the short ones are… well… short and the long ones are… long!

This is the sequence of a short GOP (very, very generally speaking) and would be typical of MPEG2 compression as in DVDs:

Short GOP: I-B-B-B-B-P-B-B-B-B-I-B-B-B-B-P-B-B-B-B-I

This would be a sequence from a Long GOP most likely found on MPEG4, H.264, AVCHD etc.:

Long GOP: I-B-B-B-B-B-B-B-B-B-B-P-B-B-B-B-B-B-B-B-B-B-I-B-B-B-B-B-B-B-B-B-B-P-B-B-B-B-B-B-B-B-B-B-I

Now that you I hope, have at least an idea of how these video file formats achieve compression and smaller file size let’s take a look at them from an editing point of view.

The first possible problem for the MPEG editing software occurs in the recording stage of the original file. In the short GOP example imagine there is the tiniest error or glitch that occurs in the first B-Picture of the sequence. Every Picture after that will snowball the effect of that glitch until we hit the next complete I-Picture because they use each other as reference points.

Now imagine the same glitch occurring in the first B-Picture of the Long GOP sequence…yikes that’s 20 Pictures of compounding error until the next I-Picture!

Video playback software will not usually be concerned by these errors because part of the playback software function is to detect and correct such errors on the fly so for playback… no problem!

However, it is not the task of video editing software to perform that function, it is designed to edit the video file which is a far more complex procedure. If it is trying to make a cut, insert a transition or apply an effect to a part of the video file that has an error then it may… and usually does, choke!

Similarly MPEG editing software is designed to render a new video file once you have finished your masterpiece. Very often you will get failures, glitches or computer freezes because the video editing software has hit some hidden data error within the original files… and just falls over when it hits that point.

Worse still you can get an MPEG2 or MPEG4 file that slowly goes more and more out of sync with the audio.

Finally let’s imagine you are doing some MPEG2 editing or MPEG4 editing and you want to make a cut at a specific point. Unseen to you is the fact that this particular cut will occur exactly in the middle of a group of B-Pictures.

We know already that these are not full pictures, they are a little data and reference to other pictures…right? So how is the video editing software going to do that? It is quite literally trying to make a cut where there is almost no picture!

Take that example and apply it then to the Long GOP sequence that you would find in the new very highly compressed formats especially in high definition. You would be trying to make a cut in the middle of nowhere.

To do that the video editing software has to use all the available information to create an I-Picture at the cut point so that a new GOP can be started… the miracle is that not only can it be done, it can be done on a consumer level video editor! Cool!

Another important issue in MPEG2 editing and MPEG4 editing is to ensure that the original video is NOT re-encoded. MPEG2 compression and MPEG4 compression have their existing flaws and every time they are re-encoded the image quality slightly degrades.

That is why is is vital to only use MPEG editing software that has a “smart encode” type feature that can identify those parts of your project that do not need to be re-encoded and to simply copy them to retain quality.

I hope that at least sheds some light on to the current difficulties in MPEG2 editing and MPEG4 editing along with all the other new highly compressed video formats.

My advice to keep you out of trouble?

Right now MPEG2 editing has been around for quite a while and most of the mainstream video editing software can handle it quite well. Time is on its side.

HDV is simply MPEG2 editing with the volume turned up to 11. Although currently it is still slightly glitchy it will settle very quickly and is a safe bet.

All the rest… MPEG4 editing , MOV, H.264, FLV, WMV… and on and on still suffer badly from the problems caused by long GOPs and very high compression. This will take longer to sort out but it will get sorted.

Clearly bottom of the heap for video editing (top for file size and quality!) is AVCHD. AVCHD is still a pig to edit and requires huge computer resources for both editing and playback. I know there is a lot of attention on it right now but a solution to its problems seem a little way off yet.

If you do happen to go for MPEG2 editing or MPEG4 editing whether high defintion or not then your needs may well be served best by specialist MPEG editing software.

If that is the case then there is no question as to which one.

Although it has never been part of the mainstream of video editing software Womble MPEG Video Wizard DVD was the first video editor to really nail down how to edit MPEG2′s and their development has continued.

It really is a superb piece of software for dealing with MPEGs in any form. It is not as well known as some of the usual suspects in the video editing software market because of its specialist nature but if your video editing needs are mainly confined to MPEG2 editing or MPEG4 editing and you want a simply great MPEG editor then Womble MPEG Video Wizard DVD is well worth a look.

Click on this link to take a look at it for yourself at Womble MPEG Video Wizard DVD or you can click this link for a full review of Womble MPEG Video Wizard DVD.

Still awake….?

All non-linear video editing software handles the video and audio assets you are using to create your project in a particular way. They all never actually touch the original video clips, audio clips or still images you are using.

Similarly they all never actually do anything until you are totally finished making all your decisions and creative choices.

Until you do finish the project the video editing software you choose will be creating a small file very similar to a text file that is a record of those choices you made.

This will usually be written in some sort of special code known only to your software. If you could read it it would look something like this. Start with black clip 5 seconds long, cross fade from that clip to video file 001, add sound file 009 at the 00.16 second mark, at 20.00 second mark reduce volume of audio file 009 and fade audio file 010 from 0 to 10 over three seconds…etc.

Obviously that looks nothing like it but I hope you get the idea!

One of the most confusing things to beginners is that they go to “File” (or similar) then hit the “Save” button and find they have created some kind of strange file with an extension they have never heard of. Whats more, no video player will play it! Of course the explanation is that they have not created a video file at all. They have created what is usually described as a project file.

I guess the origin of this is that somewhere in video editing software there had to be a differentiation between saving a project file so you can come back for later editing and saving your project to a totally new file of your completed project.

So just to clarify the terminology here, “saving” refers to saving a work in progress and saving the notes of what you want the program to do and all your decisions regarding the project.

“Rendering” means to take all the decisions you have made and to create a totally new video file encompassing those decisions.

How you render a file depends on what distribution method you are aiming for, what your viewing target will be. It could be DVD, upload to YouTube, attach to an email and send to a friend for viewing on computer, view on a mobile device…the list goes on and on.

So with regards to the rendering abilities of video editing software there are just a few points to make sure you check out before you decide to buy.

Video File Formats

As mentioned in the first post in this series you want to make sure that the video software you choose has the ability to render to the video file format or formats that you will be using the most. You can check here for an explanation of those various video file formats and also here for specifics on MPEG2 editing and MPEG4 editing.

Blu-Ray or DVD Disc Authoring

What you are looking for here is the ability to fully author (write and organize correctly for burning) DVDs in standard definition or in Blue-Ray if you are going for high definition playback. The program should offer about 10 to 20 preset menu templates for you to choose from that are fully customizable.

Smart Render/ Smart Encode

So now we know that rendering puts it all together and produces your final file in the format you have chosen as the viewing format.

Any of the highly compressed formats such as MPEG2 (for DVDs), MPEG4 etc invariably suffer from loss of quality when they are re-rendered or re-encoded from one format to another. This is an important point to remember. How often have you seen a video on YouTube that was almost unwatchable because of the poor quality. It doesn’t have to be that way if you understand this.

The degree of loss of quality varies but it is essential that any video editing software you choose has the ability to recognise those files it does not need to re-render and simply copy those sections resulting in the highest quality possible being retained. I’ll do some posts later on how to maintain quality for the various distribution formats but in the meantime take a look at a few video editing software packages and compare these features for yourself and your own needs.