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After a conversation with Ine on HD formats (1080i vs. 1080p), I researched the topic a bit further. Let me resume some of the things I have learned up till now:

Real HD and HD-ready

HD or ‘high definition’ as defined for screens, projectors and TV, defines 2 resolutions. The smaller one has 720 lines of each 1280 pixels, the bigger one 1080 lines of each 1920 pixels. They can be used with different frame rates: refreshed at 24 fps (a common movie standard) up to 50/60fps (often used for TV). To limit the necessary bandwidth in some cases ‘interlaced scanning’ is used: 1 frame contains all the odd lines, the next only the even lines. This effectively halves the throughput, at the cost of image quality (rapid moving lines appear jagged).
The two most common formats are:

• 720p60: 1280×720, 60 fps progressive scanning, used e.g. in USA-based HDTV broadcasts
• 1080i50 or 1080i60: 1920×1080, 50 or 60 fps interlaced scanning. The higher resolution makes it better for larger screens and movies, but the interlacing has a bad influence on fast moving images (like e.g. sports).

What kind of resolution do we have now? Regular digital TV (SD or ‘Standard Definition’) consists of 480 lines of 720 pixels each. DVD, for instance, allows for 480i and 480p. So, HD delivers at least 3x that resolution.

“HD Ready“, a label that a lot of TVs/screens carry now, just indicates that:

• The minimum native resolution of the display (e.g. LCD, PDP) or display engine (e.g. DLP) is 720 physical lines in wide aspect ratio.
• The display device accepts HD input via Analogue YPbPr1, DVI or HDMI
• HD capable inputs accept the following HD video formats: 1280×720 @ 50 and 60Hz progressive (“720p”), and 1920×1080 @ 50 and 60Hz interlaced (“1080i”)
• The DVI or HDMI input supports content protection (HDCP)

from eicta.org (PDF)

Even if the display can only show 720p, and so must ‘downsample’ an incoming 1080i signal to that lower resolution, it can be called “HD Ready”.
Continue reading ‘HD - 720p, 1080i and 1080p’