264 videos 640 ?— 480, 1.5 Mbps
MPEG-4 videos 640 ?— 480, 2.5 Mbps
Chapter 6: Advanced Programming Topics: Canvas and Video
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The bit rate refers to the amount of data that is encoded into one second of video. In general, it is the bit
rate that largely determines the file size ??” the higher the bit rate, the higher the file size. Standard
iPod-content is at 1.5 Mbps, although, as will be discussed shortly, any content you wish to stream over
the Internet should be done so at a lower bit rate. That??™s because the bit rate often is the key determinant
in the quality of playback when streaming over the Internet.
As you would expect, the higher the resolution and bit rates, the better quality the video will be.
However, if your users will only be streaming the videos for playback on iPhone and iPod touch
displays, then it makes no sense to set the resolution and bit rates beyond their capabilities. As
mentioned, the iPhone and iPod touch will scale down videos that are larger than their native 480 ?— 320
resolutions anyway, so encoding them at a higher resolution is a waste of bandwidth.
Considering Aspect Ratio
An additional issue to consider when working with video is the aspect ratio of the video. The aspect ratio
is the width:height ratio of the video image.
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