HD TV Definition: 1080p Vs. 1080i
Several high-definition television or HDTV formats are competing for supremacy as the industry standard. Two of the leading formats are 1080p and 1080i. For consumers desiring the best high-definition picture quality possible, understanding the differences between 1080p and 1080i can be useful and will help you make informed purchasing decisions.
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Native Resolution
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The native resolution of a TV is determined by the number of pixels, or individual areas of illumination, that combine on the screen to form continuous images. HDTVs designed around the 1080p and 1080i formats have the same resolution, as each format provides 2,073,600 pixels. This breaks down to 1,920 horizontal pixels and 1,080 vertical pixels on the display screen. Although 1080p and 1080i HDTVs provide the same resolution, the technology employed by the two formats is different.
Underlying Technology
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An HDTV interprets signals received from HD sources such as a cable or satellite receiver box, DVD player or Blu-ray player. A 1080p television relies on progressive scan technology, meaning the TV sends all of the frames comprising a video signal to the display screen at once. In contrast, a 1080i HDTV relies on interlacing technology, which means the TV sends video signal frames to the display screen in two separate batches or fields. The first field displayed on the screen contains even rows of video frames, while the second field contains odd rows of frames. Every 1/30th of a second, a 1080i HDTV alternates between displaying these two fields, allowing the video frames to interlace and appear as a continuous image.
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Overall Picture Quality
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Most technology review sites, including CNET and TopBits.com, agree that 1080p HDTV technology provides superior picture quality compared to the 1080i standard. The improved quality stems from the use of progressive scan technology, allowing all 1,080 lines of resolution to display simultaneously. As CNET points out, however, the quality differences between 1080p and 1080i are relatively few and -- to some viewers -- may be imperceptible. Rather than providing a sharper image, 1080p allows for smaller and more densely packed pixels. This decreases the amount of visible pixelation for viewers sitting up close to a TV.
Motion Artifacts
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One of the primary disadvantages of the 1080i HDTV format is its susceptibility to combing, or the formation of artifacts or visual disturbances surrounding moving objects on the screen. Motion artifacts appear because of the use of interlacing on the 1080i screen. When odd and even signal fields are interlaced, the timing of the frames from each field is slightly out of sync. This becomes especially noticeable when scenes are displayed that involve lots of movement.
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References
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