1.在做项目的过程中，对于volume 我们有一个volume curve，就是 0~63 step，每个step对应一个dB值，例如0step对应-90dB, 63 step对应0dB。关于这个0dB，是由客户规定的，最大的输出是9V,20W,阻抗4Ω。dB一般是负值，dBa是由分贝仪测出来的，dBa有一套专门的标准来测
2.Balance(左右) 和 Fader(前后)是用来调节左右前后音量的， 调节Balance,对左边或者邮编的dB进行减少，Fader调前后，可以见下图
3.Loudness,对于当前音量，有一个低频/高频的音量补偿，直接上代码,
;
/*take care of this value, volume table boost 18db for each step,
so when calculate the volume table + LoudnessOffset, need
attentuate 18db, so define the init value to -18*/
;
static float OffsetPoints[CalNofPoints] = {0.0F, -10.0F, -20.0F, -30.0F, -40.0F, -50.0F, -60.0F, -70.0F,-80.0F, -90.0F, -90.0F};
static float BassBoostValues[CalNofPoints] = {0.0F, 0.0F, 0.0F, 2.0F, 5.0F, 6.0F, 7.0F, 12.0F, 13.5F, 15.0F, 15.0F};
static float BassFilterFrequence[CalNofPoints] = {80.0F, 80.0F, 80.0F, 80.0F, 100.0F, 200.0F, 250.0F, 350.0F, 400.0F, 400.0F, 400.0F};
static float TrebleBoostValues[CalNofPoints] = {0.0F, 0.0F, 0.0F, 1.0F, 1.5F, 2.5F, 3.5F, 4.0F, 4.5F, 5.0F, 5.0F};
static float TrebleFilterFrequence[CalNofPoints] = {12000.0F, 12000.0F, 12000.0F, 12000.0F, 12000.0F, 11000.0F, 10000.0F, 9000.0F, 8000.0F, 7000.0F, 7000.0F};
float interpolate(float const x, uint_t const nof, float const xValues[], float const yValues[])//return y
{
float yRetval = 0.0F;
//yValues are expected to be constant rising or falling
//nof at least 2 otherwise there is nothing to interpolate
<=nof)
{
uint_t ;
] < xValues[last];
//check lower limit
]))
|| ((!rising) && (x > xValues[]))
)
{
yRetval = yValues[];
}
//check upper limit
else if ( ( (rising) && (x > xValues[last]))
|| ((!rising) && (x < xValues[last]))
)
{
yRetval = yValues[last];
}
else//interpolate
{
//find index for x value
uint_t index = ;
;i<last;i++)
{
]) )
||( (!rising) && (xValues[i] >= x) &&(x >= xValues[i+]) )
)
{
index = i;
break;
}
}
//interpolate
];
];
//check xDiff not 0
if (fabs(xDiff) <= FLT_EPSILON)
{
yRetval = yValues[index];
}
else//xDiff not 0 -> calculate y
{
const float gradient = yDiff / xDiff;
const float yOffset = (x-xValues[index]) * gradient;
yRetval = yValues[index] + yOffset;
}
}
}//check nof
return yRetval;
}
bool_t CavDiranaRoutingCfg::getLoudnessCurveBoost(uint16_t filterID, uint16_t cfgID, float volume, float& loudnessBoost) const
{
bool_t retval = true;
if(m_isLoudnessEnable == true)
{
;
EFilterID filtertype = static_cast<EFilterID>(filterID);
loudnessBoost = ;
//volume -> loudnessBoost
OverallOffset = LoudnessOffset + volume;
if (filtertype == FILTER_LOUDNESS_BASS)
{
loudnessBoost = interpolate(OverallOffset, CalNofPoints, OffsetPoints, BassBoostValues);
}
else if (filtertype == FILTER_LOUDNESS_TREBLE)
{
loudnessBoost = interpolate(OverallOffset, CalNofPoints, OffsetPoints, TrebleBoostValues);
}
}
else
{
retval = false;
}
return retval;
}
bool_t CavDiranaRoutingCfg::getLoudnessCurveFilterPrm(uint16_t filterID, uint16_t cfgID, float volume, float& frequency, float& quality) const
{
bool_t retval = true;
if(m_isLoudnessEnable == true)
{
;
EFilterID filtertype = static_cast<EFilterID>(filterID);
quality = ;
frequency = ;
//volume -> bass filterprm
OverallOffset = LoudnessOffset + volume;
if (filtertype == FILTER_LOUDNESS_BASS)
{
frequency = interpolate(OverallOffset, CalNofPoints, OffsetPoints, BassFilterFrequence);
}
else if (filtertype == FILTER_LOUDNESS_TREBLE)
{
frequency = interpolate(OverallOffset, CalNofPoints, OffsetPoints, TrebleFilterFrequence);
}
}
else
{
retval = false;
}
return retval;
}
4.Adjustable Bass, Midrange, and Treble tone controls. 是对低频中频高频的一个调节
The bass tone control shall have the following characteristics:
fcenter = 80Hz
Filter: Shelving type, 1st order
The midrange tone control shall have the following characteristics:
fcenter = 775Hz
Filter: Peaking type, 2nd order, Q value calibratable with initial value of 1.1
The treble tone control shall have the following characteristics:
fcenter = 8kHz
Filter: Shelving type, 1st order
5.Source Offset
按照需求，对于不同的source，有不同的音量输出要求，在原来的音量上面进行一个dB值的调整