Screen resolution / image quality on iDevices

Apple Ipad 16gb tablet
July 7, 2010 at 13:00:48
Specs: Macintosh
A quick reference guide for idevices. In order to get the best movie size and quality you need to know your device screen quality.

iPad: 1024 × 768 pixels on a 9.7 inches screen.
iPhone 4: 960 x 640 pixels at 326 ppi; on 89 mm 3.5 screen.
iPhone 3.0, 2.0 and 1.0 and iPod Touch
480 x 320 pixels at 163 ppi.89 mm 3.5 in screen.

Leave the frame rate "Same as source"
ppi: pixels per inch
Bitrate is data over second.
High image complexity: Higher color diversity and more details.

A lower resolution and a less complex image needs lower data rate or bitrate. An image with a great complexity needs higher resolution and higher bitrates. Lower image complexity accept better a lower bitrate and resolution.

Use 700 - 1200 bitrates for 720 x 480 ppi for general good quality or 1200 - 2500 bitrates for excelent video quality.

Use 1500 - 2500 bitrates for good quality on resolutions up to 1280 x 720 ppi.

A lower resolution video with a high bitrate may look better than a higher resolution with low bitrate.

Never go from a lower resolution video format as a DVD to a higher HI-DEF one.


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#1
July 8, 2010 at 12:04:18
Great, but how do I know the image complexity in order to set
the bitrate. Is it some general apretiation of the movie or there is
a more specific way to find out?

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#2
July 8, 2010 at 13:07:10
Well, I used this concept because this is something you get to know very well when you are working with images and is some topic I don't see on manny general video guides. I am working on a How to with an image comparison.

A higher Image compression reduces details, soften edges and reduce color depth. But if an image is light on color and/or details it should be easier to compress at a lower bitrate setting.

Another way to notice this is if a lower complexity image is the same size, lets say 300k, compared to a very complex image the simpler image will have less compression and better quality.

The whole point is, don't be surprised with differences in megabytes size and quality on movies with different image content. But this is just evident on movies with the same time in seconds or minutes.

An example is a cartoon movie versus lets say a Harry Potter movie. Given the same resolution, duration and image quality settings Harry Potter should be heavier.


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