1 Audio Channels n Number of audio channels
1. Audio Channels n Number of audio channels determines number of waveforms in a recording n Two relevant types of recording Mono recording • Contains one audio channel • Requires half the amount of storage space for stereo recording Stereo recording • Contains two audio channels • Offers richer listening experience A stereo audio file A mono audio file
2. Audio File Formats n Common Audio File Formats Audio file format Wave Format MIDI Format MPEG Audio Format Windows Media Audio Real. Audio/Real. Media Advanced Audio Coding File extension . wav. mid. mp 3. wma. ra /. rm. mp 4 /. m 4 a
2 Audio File Formats n Wave Format (WAV) n Native audio format in Microsoft Windows n Gives the best audio quality but has the largest audio file size n For example, the file size of four-minute CD -quality stereo recording 40. 37 MB Huge file size, not suitable to use on the Web
2 Audio File Formats n Wave Format (WAV) zoo mi ng A visual presentation of an audio wave zoo ng i m
4. 2 Audio File Formats n MP 3 n MPEG-1 Audio Layer-3 (MP 3) n Popular standard for audio compression n Supports small file size and high sound quality n Compresses storage space by removing inaudible differences in sound signals
2 Audio File Formats n MP 3 n Bit rate n. Determines the audio quality and file size n. In general, higher bit rate → better audio quality Quality Encoding bit rate File size CD 128 kbps 2. 95 MB FM radio 64 kbps 1. 47 MB Audio quality vs file size for an MP 3 file storing a 3 -minte song
2 Audio File Formats n MP 3 n Streaming n. A technology in which the downloaded portion of an audio file can be played immediately n. MP 3 supports streaming n Playing MP 3 with n. Windows Media Player n. MP 3 playing software n. Mobile MP 3 players
2 Audio File Formats n Windows Media Audio (WMA, ASX) n A compressed streaming audio format developed by Microsoft n The next most popular format after MP 3 WMA – a popular format for online radio live broadcast
4. 2 Audio File Formats n Real. Audio/Real. Media (RA/RM) n A streaming audio format developed by Real. Networks Real. Player n Playing RA/RM requires audio decompression software n Example n. Real. Player n. Can be downloaded from http: //www. real. com
2 Audio File Formats n Advanced Audio Coding (AAC) n a lossy compressed streaming audio format developed by MPEG n The most advanced audio format on the Internet n Supposed to be the successor to MP 3 The Apple’s i. Pod music player supports AAC format
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