Beginner's Guide to Adobe Flash/Video/Using Flash Video Encoder
The first thing that needs to be established before making a FLV video is the target audience. The size of a video will be largely dependent on a users available bandwidth. Use the following guide to determine about what video dimension is appropriate for a certain internet connection:
- Playback from a hard drive or CD: 640 x 480
- High-speed Internet: 320 x 240, or 240 x 180
- Dial-up: 120 x 90
If you are unsure of the video size of your source video, do the following: In Windows Media Player, choose File > Properties. In Quicktime, choose Window > Show Movie Info. Figure 1 below is a dialogue box for Quicktime. Windows Media will have a similar one.
Figure 1: Quicktime movie info.
Take note of the dimension and framerate of the movie. Do not resize to a bigger dimension than its original one, otherwise the movie will incur a serious loss of quality, much like resizing an image in Adobe Photoshop to a bigger size. Resizing a video improperly -- whether it is down or up -- may also have its repercussions. Make sure that the aspect ratio stays the same, otherwise the video will become distorted.
Do not ignore the framerate. A general rule to consider is that if your video has a lot of fast motion, such as a sports video, then it is better to have a higher framerate. Be careful. The higher the framerate, the more resource intensive the video becomes, and that can lead to slow downs and a choppy video. For a movie encoded at or near 30FPS, such as NTSC video, it is recommended to keep the movie at 15FPS. A movie with a smaller framerate, such as PAL video which is recorded at 25FPS, should be encoded at 12FPS.
After establishing the size, framerate, and target audience of the video, it is time to encode it. If you are targeting Flash 8 or 9 users, then use the On2 VP6 codec. If you are target Flash 6 or 7 users, then use the Sorensen Spark codec.
After opening up Flash Video Encoder and adding the movie file to be encoded, click on the "Settings" tab. Here you will be greeted with several preset options. Ignore them. Chances are, the presets will do more damage and provide an undesired result. Click the "Advanced Settings" tab. Refer to Figure 2.
Figure 2: Flash 8 Video Encoder
The important part is to know whether you want to use On2 VP6 or the Sorensen Spark codec. As stated earlier, it depends largely on your target audience, but only On2 VP6 allows for the use of custom UI with FLVPlayback and skins in Flash Professional 8. If your movie has an alpha channel (transparency), then use On2 VP6, as the earlier codec does not support it. Select either 15FPS or 12FPS. Remember, if your video has a lot of motion, go with the higher framerate if you must.
One of the most overlooked aspects of FLV encoding is the keyframe setting. A movie with a lower keyframe setting will usually result in a larger filesize. If your video has to be as small in size as possible, a good bet is to use a keyframe setting of 5 seconds -- that is, multiply your video's framerate times 5 to get the desired keyframe interval. If your movie is encoded at 12FPS, then the keyframe interval should be 60. If you are not satisfied with the quality of the video, then reduce the keyframe interval by a second.
In regards to quality, there are a few things to keep in mind. Note, the data rate is a combination of both audio and video:
- Do not exceed 350kbps in the Data Rate field for broadband situations.
- Do not exceed 100kbps for dial-up.
- Oftentimes, a mono soundtrack is all that is required for audio. A mono soundtrack also requires less bandwidth. Generally, 48kbps or 64kbps is sufficient for audio.