This set of Video Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Compression Working Process”.
1. Which of the following is termed as reducing image data?
a) Luminance
b) Compression
c) Hue
d) Saturation
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Explanation: Compression means reducing image data. A digitised analog video sequence can comprise of a more than 100 MBPS of data. To reduce the media overheads for distributing the sequences, the following techniques are commonly employed to achieve desirable reductions in image data:
i) Reduce colour nuances within the image
ii) Remove small, invisible parts, of the picture
2. What is the range of compression achieved with no visible difference?
a) 50 % to 90 %
b) 40 % to 80 %
c) 10 % to 30 %
d) 30 % to 60 %
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Explanation: The two techniques of compression are image based compression and video compression techniques. The extent, to which these image modifications are humanly visible, is typically dependent upon the degree to which the chosen compression technique is used. Often 50 % to 90 % compression can be achieved with no visible difference and in some scenarios even beyond 95 %.
3. In which of the following compression data upon decompression doesn’t lose its detail?
a) Lossy
b) JPG
c) Lossless
d) BMP
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Explanation: In lossless compression, as the name suggests, the data upon decompression doesn’t lose its detail. Compression works by taking the advantage of redundancies. In lossless compression you don’t lose any information at all.
4. Which of the following is the example of lossless compression?
a) JPEG
b) MPEG
c) BMP
d) RLE (Run Length Encoding)
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Explanation: One of the simplest methods of compression is Run Length Encoding (RLE). Examples of lossless compression techniques are Huffman coding, Shannon Fano coding, RLE (Run length encoding), Delta coding, LZW (Lempel-Ziv-Welch) coding etc.
5. In which of the following compression the data is lost and miss out minor details?
a) Lossy
b) Lossless
c) BMP
d) Energy
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Explanation: In lossless compression the data upon decompression doesn’t lose its detail. Whereas on the other hand the lossy algorithms tend to miss out the minor details of the data involved. For the lossy compression, the information can be thrown away and still be acceptable.
6. Which of the following is the example of lossy compression?
a) JPEG
b) BMP
c) Huffman coding
d) Delta coding
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Explanation: For the lossy compression, the information can be thrown away and still be acceptable. Think of an image of Clouds. Split the image into tiny 8 × 8 blocks and you will find that some of them can be approximated by a gradient and can be stored simply as two colors and direction. Examples of lossy compression techniques are JPEG, MPEG etc.
7. What is the full form of JPEG?
a) Joint Pressure Expert Group
b) Joint Photographic Expert Group
c) Joint Picture Expert Group
d) Join Pic Expert Group
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Explanation: JPEG stands for Joint Photographic Expert Group. The file name for a JPEG image is .jpg or .jpeg. JPEG is the most commonly used format for photographs. It is specifically good for color photographs or for images with many blends or gradients. JPEG is a method of lossy compression for digital photography.
8. JPEG is not popular for web hosting of images.
a) True
b) False
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Explanation: The above statement is false. Due to the popularity of JPEG, is also accepted in most of the programs. It is quite popular for web hosting of images, for amateur and average photographers, digital cameras etc. This is mainly due to the fact that high quality images can be saved using less space.
9. What is the full form of MPEG?
a) Moving Picture Experts Group
b) Motion Pics Experts Group
c) Motion Picture Experts Group
d) Moving Photograph Experts Group
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Explanation: MPEG, on the other hand, stands for the Moving Picture Experts Group. It is a working group of experts that was formed in 1988 by ISO and IEC. It was a joint initiative between Hiroshima Yasuda of the Nippon telegraph and telephone and Leonardo Chiariglione.
10. How many bits per pixel per color do a BMP (Bitmap image) uses, which matches the resolution of most monitors?
a) 8
b) 32
c) 16
d) 64
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Explanation: A BMP (Bitmap image) uses 8 bits per pixel per color, which matches the resolution of most monitors. Each value is an 8 bit number ranging from zero (darkest) to 255 (brightest). The values are proportional to apparent light intensity, not actual intensity.
11. Which type of compression does GIF use?
a) Data
b) LZW (Lempel – Ziv – Welch)
c) Lossy
d) Energy
View Answer
Explanation: The GIF image format is a lossless except that it uses a color palette of up to 256 colors. The format is an array of 8 bit indexes into the palette. GIF uses LZW compression. LZW (Lempel – Ziv – Welch) compression is the compression of a file into a smaller file using a table based lookup with the maximum dictionary size of 4K.
12. Which of the following is the common format for exchanging raster graphics (bitmap) images between applications programs, including those used for scanner images?
a) GIF
b) PNG
c) TIFF
d) BMP
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Explanation: TIFF is an image container format. Most commonly it is used for uncompressed images when BMP cannot be used because more than 8 bits per pixel or more than 3 color components are needed. TIFF (Tag Image File Format) is a common format for exchanging raster graphics (bitmap) images between applications programs, including those used for scanner images.
13. The artifacts show the “Blockiness” in the JPEG image.
a) True
b) False
View Answer
Explanation: JPEG has a major disadvantage that the increasing compression causes an increasing degradation of the image. This is called artifacts. The artifacts show the “blockiness” in the image. The blockiness appears when the compression ratio is pushed too high. In normal use, a JPEG compressed picture shows no visual difference to the original uncompressed picture.
14. What was created as the follow-up to the successful JPEG compression?
a) JPEG 50
b) JPEG 1000
c) JPEG 100
d) JPEG 2000
View Answer
Explanation: JPEG 2000 was created as the follow-up to the successful JPEG compression, with better compression ratios. The basis was to incorporate new advances in picture compression research into an international standard. JPEG 2000 never took off for surveillance applications and is still not widely supported in web browsers either.
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