Video Encoding for the Web

The internet is a very cost-effective method of distribution for your final project, whether it had been intended as a Web Video Production or not. But the video must first be optimized for online delivery to ensure a smooth playback, and to minimize your website’s bandwidth costs. This is accomplished through a process known as Encoding.

There are two elements that need to be considered: The required File Format(s), and the Target File Size or Bitrate.

File Format

There are three main video formats currently considered to be ‘standard’ for web delivery: Flash, Quicktime and Windows Media. Each have strengths and weaknesses, but it really comes down to what your target audience is using.

This chart shows which of these formats come pre-installed on Mac and Windows machines, and the overall market penetration of the 3 formats.

Flash has become the format of choice for websites such as YouTube. Although Quicktime offers the highest quality in the smallest file size, it only comes pre-installed on Macs. Windows Media offers a large pre-installed user base, however this comes at the expense of picture and sound quality.

Often a quick conversation with your web designer can greatly aid you in making this decision.

Target File Size or Bitrate

Let’s look at a typical scenario: Your finished video is 5 minutes long. At full resolution (TV quality) your video will be about 900MB – far too large to put online! Ideally, we’d like to get your video closer to 9MB while still maintaining an acceptable level of quality in picture and sound.

The process begins by determining the Target File Size, conforming all other variables to suit. Inversely, a Target Bitrate may be established which is a factor of filesize per second of video. Multiplying this Bitrate by the number of seconds in the video will determine the File Size.

This is where the real work begins, as the Frame Size is first reduced, and the video is compressed.

Frame Size

The first step is to reduce the Frame Size. Full-quality Video is 640×480 pixels. In reducing this to between 320×240 to 480×360 pixels, we can reduce the File Size significantly. In some cases, the required Frame Size will be determined by the website in which the video will be played.

Compression

Powerful Hardware and Software are used to examine each frame of the video, essentially looking for patterns between pixels both within a single frame and between adjacent frames of video. This is accomplished by using a mathematical algorithm known as a CODEC (short for compression/decompression), and through two methods of compression known as Temporal and Spatial. The video is then decompressed by the viewer’s computer after it has been downloaded in its compressed form.

In the Temporal method of compression, the computer is looking for instances where information remains relatively the same over time. For instance, if your video consists of a person standing in front of a simple white wall, the software is able to take a snapshot of the background area and repeat it in subsequent frames (until the background changes significantly).

Spatial Compression seeks patterns within a frame. Again with our white wall as an example, instead of each pixel of white having to be ‘described’ individually, the computer can group these pixels together and call them all ‘white’.

In Summary

This may still all sound a little confusing to you, and that’s okay. We’ll understand if you just want your video to look ‘good’. Contact us and we’ll be more than happy to talk you through it.

When beginning a new Corporate Video Production, there will be two decisions to make with respect to the format of the video. The first is the Frame Rate, and the second is the Aspect Ratio of the image.

Frame Rate

You will have two options from which to choose: ‘30 fps’ and ‘24 fps’. This refers to the number of frames per one second of video, and essentially results in two different ‘looks’ to the video.

‘30 fps’ can be compared to a typical News broadcast. It is what we would consider ‘standard’ video.

‘24 fps’, on the other hand, is equivalent to the frame rate at which both Films and High-Definition Television are captured. This frame-rate has become very popular lately as it tends to lend the video a more cinematic feel, thereby raising the perceived production value. The video is actually only captured at 24 frames per second and then converted to 30 frames per second in-camera, which maintains the same cinematic feel, while eliminating any possible compatibility issues. The effect is entirely subconscious, but very real.

Aspect Ratio

Aspect Ratio is literally the width to height ratio of the video image. The two choices are 4:3, and 16:9 (also referred to as ‘Anamorphic’).

4:3 is the standard aspect ratio which you will recognize from older Televisions. This standard had been adopted to match the aspect ratio which had originally been used by the Film industry in the ‘40s and ‘50s.

But Hollywood changed, and eventually created the widescreen format. It may have taken decades for Television manufacturers to catch up, but Widescreen or 16:9 Televisions are now being manufactured and sold in increasingly higher numbers than traditional 4:3 Televisions.

When a 16:9 DVD is played on an older 4:3 Television, the image will simply be ‘letter-boxed’ – Which means that black bars will be added to the top and bottom. This is done automatically by the DVD player.

By contrast, if a DVD shot in 4:3 is played back on a newer, 16:9 Television, the image will have to be cropped on the top and bottom, stretched horizontally, or will have vertical black bars on the sides.

We Recommend

In order to ‘future-proof’ your video project, we recommend a 16:9 Aspect Ratio at 24 fps for most projects. An exception might be in cases where we are to combine this new footage with footage which has been previously shot in the 4:3 aspect ratio and at a frame rate of 30 fps.