Ask me techie stuff!

Okay, so I’m probably opening a whole can’o’worms here but I’m regularly being asked the same techie questions about file formats, codecs, bit-rates, what’s does 16:9 mean? etc.

Here’s a place where you can ask away and anytime I get time I’ll try and give an answer in simple terms.  Hopefully you’ll help others who are afraid to ask the questions….

To start you all off…

What does 4:3 and 16:9 mean?

4:3 – used to be the squarish standard size that all our TV’s used to be (and most PC monitors still are).  A 4:3 image has 720×576 pixels. You’ll have trouble finding a 4:3 plasma-screen these days.

16:9 – or ‘Widescreen’ is now the standard for broadcast TV and gives a more cinema like screen. It still has 720X576 pixels but these are squished (techie term; Anamorphic) a 1:1 ratio would give you 1024X576 pixels. If I’m designing a sequence for widescreen PC playback I generally work at 1024X576 pixels as it gives a sharper image than 720X576 stretched. 

What resolution is DVD?

Video-DVD is set to 720X576 pixels whether it’s Standard(4:3) or Widescreen(16:9).

What is a video bit-rate?

A bit-rate is the amount of ‘bits’ allowed per second of video (techie bit: one second contains 25 frames). A high bit-rate gives smoother looking pictures but also creates a large files size which takes longer to download. A low bit-rate gives a highly-compressed picture which can look blocky but is good for web-streaming on low-bandwidth Internet connections.

During the encoding process – converting video into a compressed format such as Windows Media, Quicktime, Flash, Mpeg etc – The software tries to share the amount of data(the bit-rate) between each of the 25 frames within the second.

If there’s little movement between each frame then only small changes need to be stored leading to a sharp video.

For fast moving sequences, each frame changes so there’s less data to spread across all the 25  frames and the picture looses detail and looks blocky.

What Video formats work best in PowerPoint?

I find that Windows Media 9 files (.wmv) play very smoothly in PowerPoint even on moderately spec’d PCs. When compressed with a high bit rate of 7MB+ per sec they look better than a DVD.

Can I store Data on a DVD Video?

Yes you can and it will work like a standard CD-ROM when inserted into a PC.

A DVD-Video can be played in a stand alone DVD player and also a PC with DVD playback software (Windows XP and Vista have this built into Media Player).

A DVD-Rom can only be used by a PC/Mac.

The DVD-Video and DVD-Rom parts of the disc don’t usually interact. It is possible to add web-links on a DVD-Video but these won’t work on a stand-alone player and on a PC need a specific software player to be installed. I have found that this also leads to lots of nasty incompatibilities so I don’t recommend it.

What’s a Codec?

There are lots of digital video formats e.g WindowsMedia(.wmv), QuickTime(.mov),Windows Video(.avi),Mpeg1&2 (.mpg) etc. And just to complicate things, within these formats exist other types of compressed video e.g DivX, DV, Sorenson etc. These are refered to as the Codec.

When you post a letter, as long as the envelope has the correct address and post code, the post office knows where to send it regardless of it’s contents. In this analogy the envelope is the .avi/.mov file, the post-office is the software you’re using to play/edit the file and the Codec is the piece of software required to understand/decifer the contents of the envelope.

Why do Codecs exist?

Codecs are a very useful way for software developers to make custom compression systems that will work with existing player/editing applications, without having to ask companies like Abode to support a whole new video format. Instead they wrap themselves in a standard file type eg. .avi, .mov. – this fools the application into opening the file. As the file opens the codec takes over and deciphers the file so the application can play/use it. As long as you have then correct codec installed this should be transparent to the user.

How can I edit DVDs in Adobe Premiere (CS2,3,4)?

It’s alway best not to edit direct from DVD materal as it’s already compressed, but…….there are a couple of ways…….

The quick ‘it might work’ way is to find the (large file sized).VOB files  inside the Video_TS folder, and rename them .mpg.  The files should then open directly inside Premiere but unless the audio track was PCM encoded, the soundtrack will be mute.

The alternative is to use conversion/encoding software like TMPGEnc Xpress4: http://tmpgenc.pegasys-inc.com/en/product/te4xp.html and encode them to a DV(codec) AVI file or QuickTime movie.

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4 responses

26 01 2009
Rog Marsh

What’s this DIV-X doohicky that some AVI’s have? Is it something actually quite useful, or is it just for people downloading stuff they shouldn’t???

27 01 2009
wowmedia

Hi Rog, thanks for the question.
DivX is a Codec, so before reading further take a look at the answer to ‘What’s a Codec?’. DivX is a fantastic piece of compression technology allowing you to reduce a 90min DVD(4GB) into a CDROM (around 750MB) size file without noticeable quality loss. Yes, it was originally adopted by pirates to compress and spread DVD films over the web but it’s a highly respected format used by video professionals, especially for it’s High Definition video compression. Many modern stand-alone DVD players also support DivX playback. The only reason I don’t use DivX as standard is that it requires the end user to download and install the Codec, for many Corporations with draconian IT depts, this isn’t an option.
For more info take a look at: http://www.divx.com for the free player and codec.

12 04 2009
Gus

Mark:

What camera do you use to record your presentations?

Thanks

Gus

12 04 2009
wowmedia

Hi Gus, thanks for your question.
I use a Sony Z1 HDV camera. They’re good quality pro-cameras without costing mega-bucks to buy or hire.
The useful thing about shooting HDV is that it gives you more pixels to play with 1440X1080px rather than 720x576px(PAL).
When shooting for the VR studios I turn the camera 90o and shoot sideways (so it looks like the presenter is lying across the frame). This means that when I turn them upright in the compositing process I can zoom and pan digitally from a Wide to Mid-Shot without loosing definition.
I hope this helps.

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