Comparison Between LZ77 and LZ78 - Introduction to Data Compression -Data Compression and Encryption | Summary and Q&A

TL;DR

This video lecture explores the comparison between LZ77 and LZ78 compression techniques for data compression.

Key Insights

• 🛟 Lossless data compression preserves the original data while reducing its size, whereas lossy data compression sacrifices quality to achieve compression.
• 🛝 LZ77 is a sliding window technique, whereas LZ78 is a dictionary-based technique.
• 💦 LZ77 works on past data, while LZ78 works on future data.
• 💨 LZ78 is faster than LZ77 since it only requires drawing a table once.
• 🤗 Both LZ77 and LZ78 are open source and can be implemented using C++, Java, or other programming languages.

Transcript

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Questions & Answers

Q: What is the difference between lossy and lossless data compression?

Lossy data compression reduces the quality of images, videos, or audio by reducing the number of pixels or decreasing the quality. Lossless data compression, on the other hand, preserves the original data by reducing the total length of the data without losing any information.

Q: What are LZ77 and LZ78 compression techniques?

LZ77 and LZ78 are lossless compression techniques that fall under the Lempel-Ziv (LZ) family of algorithms. These techniques compress data by identifying repeating patterns and replacing them with shorter codes.

Q: How does LZ77 work?

LZ77, also known as the sliding window technique, divides the input data into a search buffer and a look-ahead buffer. It compares the present data with the past data in the search buffer and encodes them using an offset, length, and code (OLC) format.

Q: Why is LZ78 known as the dictionary-based technique?

LZ78 is a dictionary-based technique because it uses a dictionary, which is an existing string of characters or symbols, to encode the data. It works by assigning new codes to new entries in the dictionary as it encounters them in the input data.

Q: Is LZ78 faster than LZ77?

Yes, LZ78 is faster than LZ77 because it only requires drawing a table once to encode the data. It does not need to continuously update the table as in the case of LZ77, where sliding the data is time-consuming.

Summary & Key Takeaways

• Data compression involves reducing the size of data by compressing the number of bits, characters, or symbols present. There are two types of data compression: lossy and lossless.

• Lossless data compression preserves the original data by reducing the total length of the data, while lossy data compression achieves compression by reducing the number of pixels or quality of images, videos, or audio.

• In this video, the focus is on the comparison between LZ77 and LZ78, which are types of lossless compression techniques known as Lempel-Ziv (LZ) techniques.