CODECs and Compressions

CODEC is an abbreviation for COmpression / DECompression. It is critical in developing the fan film to understand the purpose and proper use of one. Many productions spend weeks and weeks creating their wonderful works, but don't research the correct codec to use and so have a film unviewable by their potential audience.

The compression program of choice is Cleaner. It is available for both Mac and PC and should be included on the must have list. The compressors from Ulead, Adobe Premiere, and Adobe After Effects cannot come close to the ability of Media Cleaner Pro.

The downside of Cleaner is of course it's price. If you only have one fanfilm to compress, it is a lot of money to shell out. A cheaper alternative is Quicktime Pro, which is $30 and available from www.apple.com. What you pay for is a 'key' to unlock the hidden features in Quicktime, one of which is the ability to compress movie files using any codec installed with Quicktime. If you are on a budget, and do not have access to Cleaner this is a worthy alternative (as are the compressors that come with Ulead, After Effects and Premeire, etc) You won't get such a good compression as Cleaner, but you will have a lot more cash left in the bank.

What compressor should I choose?

There is definately no 'right' answer to this question, only reasons why you may want to look at one compressor over another. For this example we will talk briefly about three choices that are most commonly used on the TFN FanFilm Forum, and their pros and cons.

The codecs under review are:

Sorenson

DivX

On2 VP3

Sorenson is the most widely used codec on TFN for one unshakeable reason. Compatibility. Encode your movie in Sorenson and chances are, everyone will be able to view the file. It comes as part of the Quicktime download, and it is extremely rare anyone has great difficulty viewing your work.

There is a reason why www.starwars.com compress all of their trailers using Sorenson, and why a huge percentage of 'industry trailers' use this codec, they want as many people to view their films as possible, with the smallest amount of emails to 'support' asking for help.

Coupled with this Sorenson produces good results as well, as can be seen by viewing movies like Seeds of Darkness and Broken Allegiance (both of which use Sorenson to compress the visuals)

Below are the settings used by Broken Allegiance using Cleaner. This is a useful starting point.

(These setting apply to material sourced as PAL 25i fps 16:9 full height anamorphic. Some setting adjustments may be needed for material that is 4:3 and/or NTSC in origin.)

PROGRAMS USED:
Cleaner 5.1.2
Sorenson Video 3.1 Pro
QDesign Music 2 Pro
(All on Mac OS)

CLEANER settings:
In preferences select Data Rate Units as: Bytes per second (Bps)

IMAGE (for16x9 Anamorphic Vision)
Crop: manual
Image Size: 256x144 (small), 512x288 (large)* 16:9
Display Size: normal
Deinterlace: auto, adaptive
*(SORENSON CODEC WORKS BEST WITH IMAGE SIZES EVENLY DIVISABLE BY 16)

ADJUST
Gamma:+50, contrast:-20, saturation:+30*
*(This should help account for the PC vs MAC Gamma differences. i.e. BA looks a little too bright on a Mac & a little too dark on a PC. Best compromise.)

ENCODE
Codec: Sorenson 3 Compressor
Bit Depth: millions of colors
Frame Rate: 25fps,
Keyframes: 150
Compare Uncompressed Frames (ticked)
Video Data Rate: 2-pass VBR, limit to: 50 Total MBytes (small), 125 Total MBytes (large), peak: 200.0 Kbytes/sec*

*(These were based on what they wanted the maximum total download file size to be for each. Obviously it ends up being a balance between quality and file size. The forest scenes in the movie could certainly have benefitted from more data rate, but we felt 125 MB was pretty big already. BIG TIP: DON'T SHOOT IN FORESTS - SHOOT IN DESERTS OR SNOW LANDSCAPES INSTEAD...THEY COMPRESS MUCH BETTER. Many of the featurettes ended up having higher data rates as they were shorter in duration, and the file sizes weren't excessive. As each one had differing types of encoding needs, no one-fits-all rate works. You just have to experiment.)

AUDIO
Codec: QDesign Music Pro 2
Sample Rate: 22.050 khz
Depth: 16-bit,
Channels: stereo
QDesign Music Codec: 12 kBytes/sec, Optimize for: quality, Attack Sensitivity: 50, Spectral Spread: 50*

*(They varied the data rate for the audio on the featurettes, depending on what was important. i.e. in the Post Production & Visual FX doco we lowered the audio data rate - and thus audio quality - to give the vision more, whereas the Original Music doco we gave the audio rate more & thus the vision less.)

So there you go, follow these tips and compression is sorted out for you. But hold on, what about alternatives and why should you consider anything else?

To the more experienced eye there are a few things about this compression that need to be flagged. 1. This scheme used Sorenson Pro for the visuals, which is another programme used in ADDITION to Cleaner, and it also uses Q-Design Pro, which is yet another programme used for the Audio. Purchase all three programmes and you have industry standard compression (literally the same set-up as is used for the Star Wars and most other trailers) but you also have a serious dent in your bank balance.

So what are the basics that can be learned from the above settings?

Data rate: Adjusting this is the single easiest way to affect the size/qulaity of your files. The higher this number, the better quality the compression but also the larger the file. Conversely the lower this number is, the smaller the file will be, but the lower the image quality will be. So run test compressions until you get a movie you are happy with, where the trade-off between size of file and quality of image is acceptable to you. Remember it is always a trade-off.

Try manually adjusting the data rate and see how low you can get this and still enjoy an acceptable image. There is no accepted 'normal' for this number, it really depends on the size of your image size, and the nature of the content (if you have made a film in the woods, with thousands of visually complex leaves moving around you will require a higher data rate than you would if you shoot in a dark, plain textured room - the codec is having to work harder on the leaves than the room, so you need to increase the data-rate, and give more information per frame)

So what about the other codecs?

DivX is considered by many to produce 'better' compression than Sorenson, and when used correctly it does appear to produce smaller/higher quality files. However the alarm bells should be ringing at this point, since not everyone can successfully view DivX compressed files, so expect a barrage of emails from disgruntled potential viewers who have taken the time to download your movie, but then only see a white screen. Sure there are sites where you can go to download the relevant codec to (hopefully) get it working, but this is more trouble than the average user wants to take, so more often than not they move onto the next film.

Use DivX by all means, but expect more emails asking why people can't view your work, or less people actually downloading your work to begin with, simply becuase they don't want to risk a lengthy download with only a white screen at the end of it. 

Remember to that DivX tends to perfrm more successful on a PC than a Macintosh, since there is only an alpha version of the decoder available for Mac, and not everyone wants to install an alpha of a codec in case the bugs cause other system problems. Secondary to this, there is no solution for Mac users to actually encode using DivX movies, hence if the movie has been made on a Macintosh, it will not be possible to create a DivX version. This is another reason why you don't see more DivX versions of files on the web.

If DivX ever becomes part of the Quicktime default download, and has a cross-platform compression option, then it will become a serious contender since the actual compression it offers (when encoded correclty) are very good in terms of filesize/image quality)

on2 The story of this codec is similar to that of DivX. Used correctly it can produce very high quality compressions with very small filesizes. However, like DivX not everyone can view files compressed using on2, so again, if you choose to use this method, expect emails from disgruntled downloaders, or possibly people that simply cannot get the codec to work. Currently users of Windows XP seem to have huge difficulty viewing on2 compressed files, so again this is not an ideal all-round method.

If you do choose to compress using on2 here are a few simple tips in order to gain superior compression.

1. Set 'Keyframe every' to 99999, this way the codec works out for itself where to put the keyframes, and results in a better compression.

2. Set the datarate manually, again testing how low you can go any still retain image quality.

Test, test, test will all of these codecs to find how small you can make the file and still make the viewing experience enjoyable for the viewer (and not just a random smattering of pixels as soon as the action heats up)

So what about AVI vs. MOV vs MPEG? We cannot stress the importance of making all your online movies in either MOV or MPEG format. At TFN we prefer to present MOV files. But, MPEG is an acceptable but usually larger alternative. Stay away from AVIs because you will alienate about 50% of your viewing audience. Although Media Player works great in Windows, it works poorly, if at all, on a Macintosh. Why do all the hard just so PC users can see it? Take a hint from the pros over at Starwars.com when they released Episode 1 and 2 teasers and trailers online, stick with MOV format.

With the launch of Quicktime 6 there are other options available to. One is to compress your file using MPEG-4 video, which may well become a major industry standard for video, couple this with MPEG-4 audio, and you have a very good combination of filesize and image/sound quality, but again, you have to have Quicktime 6 in order to view this, which not everyone currently has, and not everyone wants to take the time to download.

To summarise:

If you are going for good compression, and trouble free viewing for your audience (and minimal tech-solving emails) use Sorenson to compress your files. There is a good reason why this is used, and you can do a lot worse than 'copy' the professionals. Open up any movie trailer, and (when the movie is playing) go to the information section of the file and see what settings/codecs they are using to compress, you can learn a lot from this.

If you have the space and the inclination, try compressing your movie in a couple of formats, maybe one Sorenson file, and one DivX file, or one Sorenson file and one on2 file. That way you really cover your bases and can get the best of all worlds, in terms of quality of image, filesize and compatibilty, giving the viewing audience a choice of there favourite download option.

If you have only one option, we would recommned using Soresnon, it works, and will cause you less pain in 'tech support' emails, and more satisfied viewers watching your movie. This is the reason we prefer Sorenson compressed 'mov files for all TFN fanfilms.