Datasheet

HH
VS1053B OGG VORBIS ENCODER VSMPG
2.4.2 Setting AGC
When the highest dynamic range and sound fidelity is required, AGC should be turned
off and recording gain should be set to 1 (SCI_AICTRL1 = 1024). A good example of
this would be music recording. This is particularly recommended for the “HiFi Voice” and
“Music” profiles, although there might be cases where recording level control would be
needed even with these cases.
However, in some cases it is required that the audio dynamic range is compressed.
An example of such a case is when a device should retain a uniform recording level
of a discussion of several people or of one person moving closer and further from the
recording device. In such a case, it is a good idea to use AGC.
The AGC unit adjusts signal power in such a way that the maximum sample value from
a sine wave would become as close to 16300 as possible. If the signal is too strong,
recording level is decreased, and vice versa. The maximum recording level can be set
with register SCI_AICTRL2.
When AGC is used, conservetive maximum gain values often give the best sounding
results. Example: 12 dB (SCI_AICTRL1 = 0, SCI_AICTRL2 = 4096). In some cases
more extreme values may help to make quiet speech more intelligible, but such values
may also add excessive background noise and make sound quality less pleasing.
Rev. 1.70c 2012-11-16
Page 13(39)