RLE & Dictionary Encoding

• What are the two methods of lossless compression mentioned in the video?

  Run length encoding and dictionary coding
• For what type of documents is dictionary coding ideal?

  Text-based documents
• What type of data is run length encoding more suited for?

  Compression of images
• How does dictionary coding work?

  It builds an index that records every data item along with a unique code
• What does the compressed file consist of in dictionary coding?

  The dictionary index and the sequence of occurrences
• How does the original message size compare to the compressed size in dictionary coding?

  The compressed message is 27% of its original size
• How many characters are in the original message discussed in the video?

  105 characters
• How many bits are used to store each character in the original message using 8-bit ASCII encoding?

  8 bits
• How many bits are needed to store the numbers 1 to 17 in dictionary coding?

  5 bits
• What is the total number of bits after compression for the sequence of occurrences in dictionary coding?

  230 bits
• Why is run length encoding ideal for bitmap images?

  It efficiently compresses images with many contiguous pixels of the same color
• How is the color depth represented in the example of run length encoding?

  One bit for black and zero for white
• What do frequency data pairs represent in run length encoding?

  They indicate the number of contiguous pixels of a specific color