Assessments of each case were compared with those made from uncompressed images.
At 16:1, however, although 55% of the images were rated "clearly degraded, but still adequate for clinical use", the diagnostic error rate was found to be 45% higher than for uncompressed images.This suggests that it is easy to overestimate the degree of compression that can be safely applied.
All are said to use extra recording layers to hold the 100 gigabytes of an uncompressed 4K film.
Most found that images at 6 1 compression were not discernibly different from uncompressed images.
The researchers, led by Richard Kerensky of the University of Florida, found that, for example, with 16:1 compression, the error rate for the detection of calcification was 30% higher than for uncompressed images.
The only difference is that the TerraServer has a whole lot more of them eight microprocessors and enough hard drives to store a whopping five terabytes (five trillion bytes) of uncompressed data.
In such situations, even a slight loss in image quality could have serious consequences.A compression ratio of 4 1 (which means that the JPEG file is a quarter of the size of the original, uncompressed image) does not noticeably degrade image quality.
From this and other results they concluded that using any more than 6 1 compression would lead to a reduction in diagnostic accuracy.In this section Going global Hot stuff A trip down memory lane Why JPEGs can be bad for your health ReprintsIn another study, angiographers were asked to compare compressed and uncompressed images directly.
For comparison, transferring uncompressed high-definition video from, say, a Blu-ray player to an HDTV set requires a throughput of around 3.5 gigabits a second.
In uncompressed form they total 1.4m terabytes.The researchers also calculated the amount of information generated by communications such as e-mail, radio and telephone calls—since all of this will probably be archived systematically in the near future.
An MP3 file (usually a single three- to four-minute music track) is an eleventh the size of the uncompressed original on a CD.
