[FFmpeg-trac] #4142(avcodec:new): Fourth Generation Vocoder

[FFmpeg]

#4142: Fourth Generation Vocoder
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             Reporter:  cehoyos      |                    Owner:
                 Type:  enhancement  |                   Status:  new
             Priority:  wish         |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  qcp          |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by al3x):

 From
 [https://en.wikipedia.org/wiki/CDMA_spectral_efficiency#4th_Generation_Vocoder_.284GV.29
 Wikipedia]:

 Currently, the 4GV suite offers EVRC-B and EVRC-WB.

 Enhanced Variable Rate Codec B (EVRC-B) is a speech codec used by CDMA
 networks. EVRC-B is an enhancement to EVRC and compresses each 20
 milliseconds of 8000 Hz, 16-bit sampled speech input into output frames of
 one of the four different sizes: Rate 1 - 171 bits, Rate 1/2 - 80 bits,
 Rate 1/4 - 40 bits, Rate 1/8 - 16 bits.

 In addition, there are two zero bit codec frame types: null frames and
 erasure frames, similar to EVRC. One significant enhancement in EVRC-B is
 the use of 1/4 rate frames that were not used in EVRC. This provides lower
 average data rates (ADRs) compared to EVRC, for a given voice quality. The
 new 4GV Codecs used in CDMA2000 are based on EVRC-B.

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Ticket URL: <https://trac.ffmpeg.org/ticket/4142#comment:2>
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