PRACTICAL DV FILMMAKING

Practical DV FilmMaking

• Overview
• Inside video
• Films and how they work
• Pre-production
• Production tools
• Production aesthetics
• Post-production tools
• Post-production aesthetics
• Careers and distribution
• Mapping the industry
• Glossary of film and video terms

10 For unpredictable films where the content varies throughout, use a compression program to find the peak data rate. This lets you limit the data at specific places and avoids overloading the end-user's computer or device.

Encoding for the web

A good starting point is to use a Sorenson codec (part of Cleaner EZ) at 10fps (frames per second), with a picture size of 160 X 120 pixels, with 8- or 16-bit sound.

If you are creating a copy on your website that is specifically for low-bandwidth users, aim to com­press at smaller than the average dial-up modem of 56 kbps (kilobits per second) by going instead for around 35^10 kbps.

About data rates

We have talked a lot about the data rate, as it is one of the most important elements in compression, but there are some important facts to be aware of when talking about data. This is basic computer science stuff but has a potentially huge impact if you use the wrong terms. To begin with, there is a difference between a Kilobyte (with K and B in capitals, represented as KB) and a kilobit (lower case, represented as k and kb). Multimedia and video tend to go with KiloBytes, where 1K is equal to 1024 bytes, but telecommunications tend to use bits, in which there are 1000 to the kilo. The byte consists of 8 bits, so you must adjust the way you calculate the downloading ability of a modem. For example, a 28.8k modem (notice the lower case) will provide 28.8 kilobits per second (kbps), but if we measure it in bytes we see that it is 3.5 KB per second when we divide it by 8 (the number of bits in a byte).

Working out how small a file needs to be

A useful method of working out what compression you need for delivery onto CD or DVD is:

Disc space (measured in KiloBytes (KB), not MB) divided by movie length (in seconds) = KB of final movie.

For example, a film which is 10 minutes long, squeezed onto a CD-ROM with less than the full disc used up, say, 450 MB: 450 MB = 450000 KB, divided by 600 seconds, equals 750 KB per second. This means that your data rate needs to be 750 KB per second to run safely on the CD.

The Crunch

• Compression is ideal for viewing a DV movie on the web or putting it onto CD or DVD

• Know what kind of movie each codec is best suited to

• Customize your own compression to suit your movies - use compression software

• View your movie when compressed to check quality

• You don't have to get involved with all the computer/data/technical stuff, just work out what aspect of the film is most important

• Compression is complicated - agreed - but it can help send your movie around more places.