Planning to export your FLV file

Although the components of streaming Flash video include several files, only one of them - the FLV file - is actually video. By thinking about the following questions as early as possible, you'll be able to plan the smoothest path to publishing your video.

What is exporting, and where does it fit in to publishing streaming Flash Video?

Exporting is the the process of saving a file with different settings or to a different file format. For Flash video, it usually means compressing a large video file from an editable format to a smaller, streamable FLV file.

Before your video can be exported to FLV format, your video must already be captured from a source such as your videocassette tape or DVD to an digital source format such as DV, AVI, or high-quality MPEG or QuickTime.

Do you want to do this yourself, or hire NIS?

If you don't have the time, tools, or desire to export video to FLV format, consider hiring NIS to do this work for you. Contact us to estimate the charges for your project.

If you want to export to FLV format yourself, you'll need to make sure you have a source format that is supported by the software that will do the FLV export. If your source video is a videocassette, you'll need to capture this video to a supported format. In addition to capture software, you'll need a video capture card or device, and, of course, a VCR. For digital tape formats, support for FIreWire (a.k.a. IEEE 1394 or, for Sony, iLink) will make the work much easier, and replaces the need for a video capture card.

Is my source video format supported?

If you want NIS to produce your FLV for you, we will need to receive a supported source format from you. We prefer videocassettes in DVCAM, miniDV, Beta, or VHS format, or DVD or mini-DVD recordings. We can accept almost any current video file format provided on a CD-ROM or DVD data disk as long as it has not been extensively compressed.

If you plan to export FLV video yourself, we recommend using 3rd party software that support double-pass encoding, which improves the video quality by analyzing it before it encodes it:

Sorenson Squeeze (see supported input formats)
On2 Flix Exporter (see supported input formats)

Adobe/Macromedia's Flash Exporter 8 is distributed with Flash Professional 8 and offers only single-pass encoding. It supports the following source file types:

• Active Streaming Format (.asf)
• AVI (.avi)
• DV (.dv)
• MPEG, MPEG-4 (.mpg, .mpeg, .mp4)
• QuickTime (.mov)
• Windows Media Video

What size should my embedded video be in my Web page?

For most streaming video applications, we recommend the video resolution be 320 X 240 pixels (for video with a 4:3 aspect ratio) or 360 X 240 (for 3:2 video).

For applications where you expect your audience to have a T1 or greater network connection (such as an office intranet), consider increasing the size to a larger resolution (such as 640 X 480 or 720 X 480).

For video intended to be streamed to users with dial-up (56K) connections, consider a smaller size (such as 240 X 180 or 270 X 180).

At what transfer rate or rates to I want to delivery my streams?

This decision requires that you know your audience. While most Universities and corporate offices offer network connections in excess of 1.5 Mbps, many DSL and cable broadband connections in US households are below 500 Kbps. And many users still rely on dial-up connections, usually 56 Kbps.

Regardless of the software you use to export Flash video, you will have the choice of setting a custom delivery rates or using presets approximately in line with the following guidelines:

• 150 Kbps - low enough that all DSL/broadband viewers can watch without interruptions in playback, but video quality suffers noticeably, especially for video that has movement and details
• 400 Kbps - the conventional setting for reaching residential DSL/broadband users, though a few users will experience inconsistant playback
• 700 Kbps - Best reserved for when you know your audience has a fast network, such as the BU network.
  

What versions of Flash Player do I want to support?

The compression technology, or codec, for Flash 8 is significantly improved over Flash 7, but it has slightly less distribution than Flash 7. If you have Flash 8 on the computer you're using now, compare the quality in by experimenting with the codec settings (also, the encoding settings, if you want to compare single- and double-pass encoding for each codec):

During 2006, support for Flash 8 rose dramatically among visitors to www.bu.edu, growing from roughly 60% to approximately 92%. This is reinforced by statistics released by Adobe. Using use data gathered through September of 2006, Adobe claims 90% of US survey participants (and higher percentages worldwide) used browsers supporting Flash 8, while 94.8% support Flash 7. Even in emerging markes, Flash 8 penetration was at 83.1 percent in emerging markets in June 2006.

In January, 2007, Adobe release the Flash 9 player for Linux operating systems, with backwards compatibility for Flash 8 and Flash 7 video. This was a big step for Linux users, as there was no Flash 8 player for Linux.

Given these facts, NIS now recommends Flash 8 video as the Web standard.

How should I balance audio and video quality?

Regardless of the software you use to export Flash video, you will be able to customize the quality of the audio that is part of your stream. Assuming you are setting a fixed target delivery rate such as 400 Kbps, keep in mind increases in audio quality will come at the expense of the quality of the video. For instance, if you choose 400 Kbps for your delivery rate and 96Kbps for your audio data rate, you can expect the video component of the stream to be encoded for delevery at about 304 Kbps. This is true even when encoding with Variable Bit Rate (VBR), as is often the case. (VBR settings typically result in streams that occasionally exceed the target delivery rate by a small amount during complex scenes, and dip below the target delivery rate during less complex transitions.)

Unless music fidelity is important to your stream, consider using an audio data rate of 64 Kbps or lower. Audio at 32 Kbps might be acceptable when the audio is limited to speaking, but will sound somewhat compressed, especially through quality headphones. For 56 Kbps streaming, setting the audio rate as low as 8 Kbps is common.

Finally, keep in mind that maximizing the data rate for video is most important when there is considerable motion (either camera motion or subject motion) and texture in the subject, and less important when the subject is relatively still, such as for a podium speaker in front of a plain backdrop.