Why Compress?
File Sizes
Interlacing
Keyframes - Fast Movement

WHY COMPRESS?

It's very important that you are compressing the data of your film. It means that it won't look or sound as good as it does 'off the tape', but that it is small enough to upload and process on the internet. This means lots of people can see it, so it's just something you gotta do.

PLEASE NOTE - THE BELOW INFORMATION ONLY APPLIES TO FOURDOCS (3-5 MINUTES) RATHER THAN MICRODOCS (UNDER 59 SECONDS) - FOR MICRODOCS, YOU CAN LEAVE YOUR FILM AT 6400 KILOBITS/SEC WHEN COMPRESSING

FILE SIZES

It is very easy to mis-type a number in a box and come up with a huge output file. But the FourDocs web monkeys won't like this, and they'll reject it.

So, when you've exported your film, check how big the file is and compare it with the list below.
Remember, if your file is bigger than 130Mb YOU CANNOT UPLOAD IT. So...

If your film is....
- about 70-120Mb you're OK!

- about 130-200Mb, it's too big. You should check that you're using compressed audio, i.e. MPEG4 or Windows Media 9. If you are, then either your film is too long, or you need to reduce your audio and video bitrates to the recommended ones above.

- about 450-700Mb, you've probably made a very easy mistake to make. Check that you haven't specified a 3000kiloBYTE data rate instead of 3000kiloBITS. This is easy to do in QuickTime 6 because it mostly wants data rates in kilobytes, not kilobits. Very confusing, but easily solved.
THIS IS THE IMPORTANT BIT!
1 kilobyte=8 kilobits, so 3000kilobits=375kilobytes.
Try putting 375 in the box instead of 3000 and see what the quality looks like!

- about 1Gb or more, you haven't compressed at all. Check that you haven't just done a 'self-contained' export. And make sure that you're using MPEG4 or Windows Media instead of DV. Whilst you may well be shooting and editing in DV, it's just to big to deal with on the internet at present. You need to compress the film first.

INTERLACING

Interlacing is a method of getting faster movement in a video picture whilst minimising the amount of information required to do it.
This is done by splitting the frame into two 'fields', each one containing half the frame.
This gives better motion reproduction for the same recorded amount of information. It's how your DV camera records.

However, computers tend to prefer to have pictures recorded 'Progressive', i.e. one complete frame recorded at once.
Your editing package is happy to work with interlaced video but programs like QuickTime player and Windows Media player are not, so FourDocs plays back in this different way.

In order to make your file compatible, you must convert your finished film into progressive format, or 'de-interlace' it. This simply means merging the two fields into one frame. If you don't, then when your film plays back you will see both fields at the same time instead of one after the other. This is pretty disastrous when there is rapid movement in the picture.
The image will look like this:

Whereas, a properly de-interlaced image looks like this

:

You can see that the edge is much sharper.

The FourDocs team are working on applying de-interlacing for you, but until we've finished, we'll have to reject your film if it isn't correctly de-interlaced. Sometimes, it's done automatically, or other times it's as simple as selecting a checkbox or an option when you export. Otherwise, we recommend donwloading a very good free Mac deinterlacer from here. If you can't find the right button, ask our advice

KEYFRAMES - FAST MOVEMENT

If you have any very fast movement in your film, you may find that the picture 'breaks up' into blocks around the moving area. This is not to do with interlacing, but to do with the way the picture is compressed.

This issue arises because when the video is compressed, most frames are only recorded as the difference from the previous frame. This is normally fine but if you have very rapid motion, the difference is so great that it is not possible to store it properly within the limits of the compressed file. As a result the picture breaks up.

Certain frames (called Keyframes or 'I-frames') are stored as complete frames though. So it is fairly simple to get around this movement problem -
simply increase the number of keyframes in the encoded file. There will then be less difference to keep up with between each frame.
The downside is that keyframes take more space to store, but you have limited the total size of the file (using the Bitrate setting) so in the end, the picture won't look as sharp, but at least you won't have big blocks everywhere.

You can usually increase the number of keyframes simply by finding the 'Keyframes' setting (usually in Advanced Options for the video compressor you're using) and increasing the number there.
HOWEVER, sometimes the program doesn't ask you for the number of keyframes in a given amount of time but the INTERVAL BETWEEN keyframes. If this is the case then you need to REDUCE the number . So, you're reducing the space between keyframes and hence increasing the overall number of them. Result!

ARE YOU COMPRESSED NOW?

These are the main problems FourDoccers are encountering. Make sure you check our Basic Settings guide too. But if they aren't solving your problems, email us and we'd love to help you.