Web Video: An Overview

The Web has become a valuable vehicle for publicising and displaying the work of filmmakers, and for those of you out there interested in the process, this article presents a general overview of moving images on the Web, and in particular, our experiences with getting film clips up and running on our site.

How it Works

The method that is of most use to filmmakers, who want to put clips from film or video-based productions up on the web, is bitmap-based web video. This method splits the video up into a series of image files made up of rows of pixels plus audio files, sends them down the modem line, reassembles them at the other end and plays the clip. Various transmission and compression techniques can be used to decrease download times and improve playback at the other end.

To view the clip, the end user, or visitor to your site, requires a video player to be installed on their computer. The most common players are Quicktime, RealPlayer, and Windows Media Player. In general, these players will only play files created specifically for them. Windows Media comes preinstalled with Windows. The others generally have to be downloaded, and it is recommended that you have the latest versions on your system.

Transmitting the Clip

Clips may be transmitted and displayed in two different ways, these are Full Download or Streaming:

Full Download

This method requires the end user to download most or all of the video file before it can be played. The viewer has to wait until the whole clip is downloaded.

The advantages are that it allows for higher quality clips, as the playback does not rely on download speed. This method does not require any special software at the Internet Service Provider (ISP or, sometimes called, web host) end, and clips can be embedded into web pages the same way as still graphics files.

The disadvantage is that the clips need to be kept quite short (1-2 minutes maximum) to achieve acceptable download times.

Both Quicktime and Windows Media Player can use this method.

Streaming

Streaming involves displaying the video frames as they are downloaded. Usually the player builds up a "buffer" of 30 seconds or so of video before starting the clip. You can often get a choice of clip types that are optimised for different modem speeds.

The advantages are that the viewer does not need to wait for the entire clip to download and much longer clips can be displayed. The player can theoretically keep playing for as long as it needs to. In reality, however, there are limits on the file size that can be stored on the ISP site.

The disadvantage of this method is that special software is required by the ISP to play the clips. ISPs charge more for this service, and not all of them have the software installed. The other disadvantage is that the clips are generally of lower quality than those using the Full Download method. Streaming is also used for 'live' web broadcasts, where file size is not an issue.

RealPlayer and Quicktime can use this method.

Getting Your Film Onto the Web

The following steps are required to get film clips onto a website:

Video Capture

The video clip has to be transferred from the tape, film etc into the computer. As the final clip is generally of much lower resolution than the original, a VHS copy of the film can be used, or a direct feed from a video camera. The video signal must be inputted using a Video Capture system. The most common one for doco makers would be Firewire, which is supported by most cameras and by Macintosh computers. Video Capture cards can also be used, such the Miro or Perception cards. Firewire cards are also available for PCs. If all you want to do is web video, there are also cheaper options available.

The clip should be captured at a least PAL resolution if the computer can handle it; this can always be reduced later. The highest quality audio capture setting should also be used, as this can make a MAJOR difference to the quality and compressibility of the sound in the final clip. This is particularly important with dialogue and voiceover.

The captured file needs to be in a compatible format with the compression software (see Compression for more on this).

Editing

Once captured, clips may be edited down to the required length. Most video capture systems come with video-editing software of some description, and a high-end system such as Final Cut Pro or AVID is not really required unless you need to use its advanced features.

To retain maximum video quality, the clip should remain in the same format, resolution, audio rate etc as it was when captured. This will minimise the loss of quality through unnecessary processing.

Compression

Compression reduces the size of the video and audio files to optimise the playback rate, picture and sound quality.

In general, most players (for instance Quicktime) will only play video clips in their own format. This means the person making the clips is required to have the 'development' software to ready them for the Internet. This can to be purchased on the suppliers web site (if you have a credit card) and downloaded, or can be bought in a computer store.

To prepare it for the web, the clip - already edited to the required length - is imported into the package, and the output requirements are set.

A range of video and audio compressors are available. These vary in their ability to handle different types of images (eg. full motion or relatively still scenes), and sounds (dialogue, music, location sound etc). Some also require faster computers to handle the processing at the viewer's or visitor's end, and some are only compatible with the latest versions of their respective players. You basically have to experiment to find the best settings for the clips you have and the audience you want to reach.

Other Output Settings

As well as the video and audio compressors, other settings include image size, frame rate and audio rate. Several versions of clips can be produced optimised for different modem or processor speeds, and some development packages allow the website to automatically detect the speed of the computer and play the clip to suit that computer. This is another area open to some experimentation about what works for you.

Putting the Clip up on the Site

Full Download clips may be embedded in web pages in the same way as still images and animated gifs. The development package will usually create any HTML code that is required to be included with the file. When the page loads, the web browser will detect the clip and start up the appropriate Player.

Streaming clips require special coding. We initially investigated using RealPlayer for our clips, but found that setting up the web page to play the clip was very tricky, and we eventually gave up and went to Quicktime. As the ISP charges for streaming video, using a full download clip was also cheaper.

Once the clip is up on the site, it can be accessed as required.

How We Do it

At Documenter, we use a Miro video capture card to capture the clips from VHS. However, besides being a tad unstable, the Miro system is designed for broadcast quality video and there are much cheaper options available if all you need to do is web video capture. The clips are edited in Premiere (which came with the Miro card). Again, there are much cheaper options available for editing web video.

The edited clips are imported into Quicktime Pro 4 (U$39.95), and compressed using the Sorenson Video Compressor, which seems to produce the best quality image, allowing us to make the image smaller and still retain enough clarity to see what's going on. However, Sorenson does require a Pentium or PowerMac system for good performance. Sorenson will only work with Quicktime 3.0 or above.

For audio, we use IMA 4, as this works well with most clips. There are special audio compressors that can work better for clips that only contain speech or music. IMA 4 will also only work with Quicktime 3.0 or above.

The clips are exported as Quicktime (.mov) files. Resolution is generally 200 x 150 pixels which, when used with the Sorenson compressor, still allows you to read subtitles!

A relatively low frame rate can be used, and we find that 10 frames per second produces acceptable picture quality.

Providing the quality of the original sound is good, audio speed is generally set at 8 kHz - though again this can be varied as needed, and does not have as great an effect on download speed as the video settings do.

We try to keep the files under 2 megabytes, which is a realistic size for most modems. The Quicktime player will also look at the download rate, and start playing the clip when it thinks it has enough data for continuous playback. As such, Quicktime Pro allows you to review the required download rate for the final clip, and adjust the output settings if required.

The still image that initially appears when the web page loads up is called a "poster" movie. This is a single frame quicktime movie, usually a frame from the main clip, that is used because it loads quickly, and is coded as to not require the full quicktime player to be displayed. Each video clip requires a poster movie and a main quicktime clip. The HTML code used to embed the clips on the page allows the full clip to be loaded and played when the poster movie is clicked with the mouse.

The Quicktime files need about 3 lines of HTML code surrounding them on the webpage to allow the system to detect and play them.

This is the code we use:

If other people have different or further advice and/or experience with the systems email us and we will place your tip along with this article.

Reprinted with permission from author The Documenter, whose Web site contains good information on utilizing the digital medium.