Audio compression Skills audio compression Concepts qualityfile size

Audio compression Skills: audio compression Concepts: quality-file size trade off, capture-editcompress, 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 – User skills

Audio processing work flow Record Edit Compress Distribute

Which recording is not compressed? 1 2 3 4 5 6

Which suits your application? No. 1 Data rate 320 kbps File type. mp 3 File size 114 k. B 2 Original . wav 245 k. B 3 64 kbps . mp 3 23 k. B 4 16 kbps . mp 3 6 k. B 5 128 kbps . mp 3 46 k. B 6 8 kbps . mp 3 3 k. B

Compressing with Audacity File > Export > Options

Quality rules of thumb Bit rate 8 kbps 16 kbps 32 kbps Quality telephone shortwave radio AM radio 64 kbps 96 kbps 128 kbps FM radio near CD CD

All files can be compressed Image Numeric Program Text Which require lossless compression? Audio Video

Summary

Self-study questions 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 before distribution in audio, image and video processing? If we do not lose information when doing lossless compression, what changed to reduce the size of the file? (Hint: see http: //cis 275 topics. blogspot. com/2010/10/datacode-information. html).

Resource Configure Audacity to export. mp 3 files: http: //cis 275 topics. blogspot. com/2011/03/configureaudacity-to-export-mp 3 -files. html Free software (reviews and links) for doing lossless compression: http: //www. techsupportalert. com/best-free-filearchiver-zip-utility. htm