Mp3 and Mp4

Agenda

• What is Mp3 • How it works• What is Mp4

What is Mp3…

• Mp3 designed by the Moving Picture Experts Group

• Mp3 is the acronym of MPEG-1 Audio Layer 3

• Digital Audio encoding format

Why we need to compress audio…

• The data on a CD uses an uncompressed, high-resolution format

• 44,100 samples/second * 16 bits/sample * 2 channels = 1,411,200 bits per second

• So an average song consumes 32MB of space

• The compression ratio of Mp3 is 12:1 • So, a 32MB song on a CD compresses

down to about 3 MB.

How Mp3 achieves compression…

• Mp3 uses a technique called perceptual noise shaping.

• We can choose how much information an MP3 file will retain or lose during the compression process.

• The standard bit rate for MP3 files is 128 kbps, and this represents a good compromise between sound quality and file size.

Other Audio compression formats...

• MPEG2 Advanced Audio Coding (AAC)• WMA• OGG• RA• Lossless data compression formats:

Apple Lossless Audio Codec (ALAC) , DTS-HD Master Audio, Dolby TrueHD

What is Mp4…

• Mp4 is the acronym of MPEG-4 Part 14• Mp4 is Media Container format.• Used to store digital audio and digital

video, especially those defined by MPEG, also used to store subtitles and still images.

• File name extension: .mp4/.m4v/.m4a

• Video: MPEG-4 Part 10• Audio: Advanced Audio Coding

(AAC),Mp3• Subtitles: MPEG-4 Timed Text

Other Container formats…

• Microsoft ASF (Advanced System Format)• QuickTime .Mov format• Microsoft AVI format

Does MP4 mark the end of MP3?

Thank you!!Thank you!!