Post on 18-Dec-2015
Audio compression
Skills: Audacity compression
IT concepts: quality-file size trade off, capture-edit-compress, lossy versus lossless compression
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.
Where does this topic fit?
• Internet concepts– Applications– Technology– Implications
• Internet skills– Application development– Content creation (audio)
All data types are compressible
Image
Text
Numeric
Audio
Video
Bit Depth Sample Rate 1 minute 3 minutes
16 44,100 10.1 Mb 30.3 Mb
16 48,000 11.0 Mb 33 Mb
24 96,000 33.0 Mb 99 Mb
MP3 File 128 k/bit rate 0.94 Mb 2.82 Mb
Examples of files sizes for stereo recordings
MP 3 is a compressed format.
1. click to play
2. click to play
Which sounds best? Worst?
Audio fileFile size(Kbytes)
Bit rate(Kbits/s)
Play low quality (.mp3) 16 16
Play original (.wav) 676 688
1. play2. play3. play4. play5. play
Which sounds best? Worst?
No. Data rate File type File size
1 320 kbps .mp3 112 kB
2 Original .wav 233 kB
3 64 kbps .mp3 26 kB
4 16 kbps .mp3 10 kB
5 128 kbps .mp3 47 kB
Record and edit at high quality
Export > Save as MP3 > click Options
Compress for distribution
Variable bit rate
Bit rate Quality
8 kbps telephone
16 kbps shortwave radio
32 kbps AM radio
64 kbps FM radio
96 kbps near CD
128 kbps CD
Quality rules of thumb
Lossy compression
Information is lost– the original cannot be recovered
Audio compression
Skills: Audacity compression
IT concepts: quality-file size trade off, capture-edit-compress, lossy versus lossless compression
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.
How many bytes in a three minute, CD quality song?
How many bytes in a three minute telephone quality conversation?
What is the final step in audio, image and video processing?
A few questions
Image
Text
Numeric
Audio
Video
Which data type(s) is/are suited to lossless compression? Lossy compression? Why?