AET 1380 Digital Audio Formats Consumer Digital Audio Formats CDs --44.1 khz, 16 bit Television 48 khz, 16bit DVD 96 khz, 24bit How many more measurements does a DVD take? Bit Rate? Sample rate? Is it better to reduce bit rate or sample rate relatively? Channels Audio file can support one to six channels of audio formats. Mono one channel Stereo two channels Some others three, four channels Quad sound, 70s Six channels 5.1-channel surround sound. More multi-channel formats announce in the coming years. CDs Standard music CD: Sampling Rate: 44.1 khz 16 bit-bit depth 2-channel stereo Data transfer rate = 2 16 44,100 = 1.4 Mbits/s 1 hour of music = 1.4 3,600 = 635 MB
CDs Analog sound data is digitized by sampling at 44.1 khz and coding as binary numbers in the pits on the compact disc. As the focused laser beam sweeps over the pits, it reproduces the binary numbers in the detection circuitry by the different colors reflected. Pits cause laser to reflect at angle of incidence. Rainbow patterns you see is due to the different reflections of white laser beam from the irregular surfaces. Pits and lands burnt into aluminum layer. Arrangement on the CD Pits are arranged in long spiral, starting at center and spiraling outward toward edge Another view CD Geometry From: How Stuff Works http://entertainment.howstuffworks.com/cd1.htm
SACD Super Audio CD is a new format created by Philips and Sony. It looks like a CD but the audio is of much higher quality. Audio is captured/played back through a new process called Direct Stream Digital (DSD) which uses a high sampling rate of 2.82 MegaHertz (respresenting frequencies up to 100 khz) and a dynamic range of 120 db. A single, hybrid SACD disc can have a high density stereo mix, a multichannel (surround) mix and the standard CD layer. 96kHz sample rate DVDs 24 bit bit rate 4.7 GB Dual layer 9.4 GB Will more than likely be double-sided DVD Technology Density of pits up 4 times, plus 4 surfaces holds 16 times as much as CD Data compression extremely important for DVDs avoids redundant coding of repetitive information (e.g., still scenes, backdrops, even music waveforms) DVD-Video DVD Technology Movies with a surround audio soundtrack 5.1 audio compressed or stereo uncompressed DVD-Audio -up to 24 bit, 96 khz with 6 channels -176.4 bit, 192kHz with 2 channels
CD: 780 nm ~660 MB DVDs DVD: 640 nm ~11 GB How Stuff Works: http://www.howstuffworks.com DVDs DVDs are ideal for: Simultaneous encoding of digital video and surround sound audio Multi-channel surround sound Data and access intensive video games High density data storage DVD-Video Movies with a surround audio soundtrack 5.1 audio compressed or stereo uncompressed DVD-Audio (DVD-A) -up to 24 bit, 96 khz with 6 channels -176.4 bit, 192kHz with 2 channels (4x better than 44.1 Hz of CD) Blu Ray Discs A single-layer Blu-ray disc, which is roughly the same size as a DVD, can hold up to 27 GB of data -- that's more than two hours of high-definition video or about 13 hours of standard video. A double-layer Blu-ray disc can store up to 50 GB, enough to hold about 4.5 hours of high-definition video or more than 20 hours of standard video. And there are even plans in the works to develop a disc with twice that amount of storage. Can hold more info because it uses a shorter blue laser. - From Howstuffworks.com Digital Tape Recorders Digital tape recorders store record pulses of magnetism as 1 s and 0 s. Types DASH Digital Audio Stationary Head Rotating Head DAT (2 Track) MDM (True Multi-Track) Alesis ADAT Tascam DA-88
Digital Tape Recorders ADAT The ADAT uses the S-VHS 1/2 inch tape format. This tape is similar in design to the tape used in consumer VCRs. Inside the Computer: Digital File Formats formats Lossy Compression MP3s use LOSSY compression only meaning that it removes information from the input in order to save space for storage and internet transmission. The information that lossy compression loses is the information deemed least important to the file (the sounds that most people can't hear) In music, this tends to be the very high and very low frequencies that are not considered to add as much to the music as the range of frequencies in between. The most notable artifact of lossy audio compression is "muddy" sound. formats MP3 most common Stands for MPEG 1 Layer 3. Variable bitrates 128, 160, 192, 256, 320 Many listeners accept the MP3 bitrate of 128 kilobits per second (kbit/s) as near enough to CD quality for them; this provides a compression ratio of approximately 10:1.
formats LOSSLESS compression works by encoding redundant information with symbols and equations that take up less space. Works by reducing information redundancy Can be 70-80% size of original file. Formats include FLAC, APE, SHN and Apple Lossless. formats Digital Audio Transfer Formats AES/EBU (AES3 interface) A professional specification using time division multiplex for data, and balanced line drivers to transmit two channels of digital audio data on a single twisted-pair cable using 3-pin (XLR) connectors. S/PDIF (Sony/Philips digital interface format) A consumer version of the AES3 (old AES/EBU) digital audio interconnection standard based on coaxial cable and RCA connectors. Digital Audio Transfer Formats Lightpipe (Optical) Word Clock
Billy Jean formats Listening Exercise #1 24 bit/ 96 khz DVD-A quality #2 16 bit/44.1 khz CD quality #3 320 kbps MP3 file #4-192 kbps MP3 file #5-160 kbps MP3 file #6 128 kbps MP3 file common internet quality (Kazaa, etc) Make notes about high sounds (shaker, vox) and low sounds (bass drum, bass) and overall sound quality.