1.3 InfoRepr&Multimedia.compression Flashcards
What is lossless file compression?
A compression method where the original file can be fully restored after decompression.
What is lossy file compression?
A compression method where some original data is lost during compression, making it impossible to fully restore the file.
What is JPEG compression based on?
The inability of the human eye to notice certain colour changes and hues.
What type of files use MP3/MP4 compression?
Music and multimedia files
What is audio compression?
A method to reduce sound file size using perceptual music shaping.
What is perceptual music shaping?
A technique that removes sounds outside the normal human hearing range to reduce file size.
What is bit rate?
The number of bits per second that can be transmitted over a network, measuring data transfer speed.
What is Run-Length Encoding (RLE)?
A lossless file compression technique used to reduce text and photo file sizes.
Why is file compression important?
To save storage space and reduce transmission or streaming time.
Why is lossless compression used for critical data files?
Because it preserves all original data, ensuring no loss of important information.
How does lossy compression decide which data to remove?
Algorithms determine which parts of the file are essential and which can be discarded without significant impact.
What is MP3 compression used for?
MP3 compression is used to reduce the size of music and sound files by about 90% while maintaining acceptable quality.
How does MP3 compression achieve such high size reduction?
It uses perceptual music shaping to remove frequencies outside human hearing and eliminate quieter overlapping sounds.
Why is MP3 considered a lossy compression format?
Because some original data is permanently lost during compression, meaning the original file cannot be fully reconstructed.
What is bit rate in MP3 compression?
The number of bits per second used when creating the file, typically ranging from 80 to 320 kbps, affecting sound quality.
What is the main difference between MP3 and MP4 formats?
MP3 stores only sound files, while MP4 supports multimedia, including music, videos, photos, and animations.
How does MP4 compression benefit video streaming?
It allows videos to be streamed over the internet without significant loss of quality.
What is the impact of JPEG compression on images?
JPEG compression reduces both the file size and image quality by a factor of 5 to 15, depending on the original quality.
Why is JPEG compression considered lossy?
Because once the compression algorithm is applied, the original image cannot be reconstructed.
Can vector graphics be compressed?
Yes, scalable vector graphics (.svg) can be compressed as they are defined in XML text files.
What is Run-Length Encoding (RLE)?
A form of lossless file compression that reduces the size of repeated adjacent data by encoding them into two values: count and data item.
When is RLE most effective?
When there are long runs of repeated data, such as consecutive identical pixels in an image or repeated characters in text.
How does RLE work with text data?
It replaces sequences of repeated characters with a count and the character itself, reducing storage requirements.
How does RLE work with images?
It replaces consecutive identical pixels with a count and the pixel value, reducing image file size.
What are general methods to reduce movie file size?
Reduce sampling rate, sampling resolution, and frame rate.
What are general methods to reduce image file size?
Crop the image, decrease the colour/bit depth, and reduce the image resolution.
