ADPCM


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Related to ADPCM: IMA ADPCM

ADPCM

ADPCM

ADPCM

(Adaptive Differential PCM) A widely used variation of PCM that codes the difference between sample points like differential PCM (DPCM), but can also dynamically switch the coding scale to compensate for variations in amplitude and frequency. See PCM, DPCM and sampling.

ADPCM for CD-ROMs
Sony and Philips set the encoding standards for the CD (Red Book) and CD-ROM (Yellow Book), and several ADPCM codecs were defined for mixing audio and data on a CD-ROM. Because of the larger sampling rates and two channels (left and right stereo), the following bit rates are much larger by comparison to the subsequent list of ADPCM codecs used for speech (the G. standards).
                        SamplingAudio          Coding   Rate    Bit RatesFormat         Method   (kHz)   (kBps)

 CD-DA (music CD)  PCM    44.1   1411.2

 CD-ROM Level A  ADPCM    37.8    604.8

 CD-ROM Level B  ADPCM    37.8    302.4

 CD-ROM Level C  ADPCM    18.9    151.2


ADPCM for Speech Codecs
The ITU has defined numerous speech codecs, some of which use ADPCM. Note the lower bit rates for these applications because of the smaller sampling rates.

Codec            SamplingG.       Coding   Rate   Bit RatesNumber   Method   (kHz)  (kBps)

 G.711    Mu-Law PCM  8    64

 G.711    A-Law PCM   8    64

 G.721    ADPCM       8    32

 G.722    ASPCM       7    48/56/64

 G.722.1  MLT        16    24/32

 G.722.2  ACELP      16    from 6.6
                            to 23.85

 G.723    (withdrawn)

 G.723.1  MP-MLQ      8    6.3

 G.723.1  ACELP       8    5.3

 G.726    ADPCM       8    16/24/32/40/64

 G.727    ADPCM       8    16/24/32/40/64

 G.728    LD-CELP     8    16

 G.729    CS-ACELP    8    8
References in periodicals archive ?
Comparison of the DPCM and ADPCM system is shown in Fig 6.
We are in the process of adding locations to the network, which will ultimately increase traffic, and ADPCM will probably keep us going for some time.
At present, there is no world standard for ADPCM encoding, but one is expected.
User-selectable durations from 2 to 32 minutes based on 8kHz/4bit ADPCM -- Digital audio data with sample rate up to 48kHz via I2S or SPI interface -- Fast digital recording with data rate up to 1Mbits/second -- Built-in message management -- Performs address-free recording -- Stores pre-recorded audio using high quality digital compression -- Uses simple index based commands for playback -- Executes pre-programmed macro scripts (Voice Macros) for device configuration, message sequence playbacks and recordings -- Varieties of digital compression algorithm for recordings and playbacks
We will leverage our rich voice technology assets such as OKI ADPCM high quality voice compression technology, our expertise in voice synthesis accumulated for over 20 years, and our support capability that is committed to high-quality sound.
With AuriStream CSR has introduced Adaptive Differential Pulse Code Modulation (ADPCM) as an enhanced voice coding method, since it performs the same function at half the rate of CVSD (ADPCM scans at 32Kbps, CVSD 64Kbps) saving up to half the Bluetooth power on the handset; ADPCM is more accurate, and provides a much higher voice quality.
25 and ADPCM, as well implemented some of the earliest and largest private cell-based voice and data networks in Western Europe.