Waveform Average value

[PeterAP]

Hello all!
It's possible to read RMS value.
How it can be possible to calculate average value?

Thanks!

 

[PaulStoffregen]

It's possible to read RMS value.

Yes, it is possible.

In fact, the Teensy Audio Library has a RMS analysis feature (link is to right-side documentation panel) already built into the library.

How it can be possible to calculate average value?

Average value is computed by adding all the items and then dividing by that sum by the number of items.


Maybe you already knew that? If you want a more useful answer, put a little more effort into your question. We're real humans here, capable of understanding and really helping, but only if you give us something more to understand your needs than these simple questions.

 

[PeterAP]

Thanks, Paul for response!
I', m really sorry for very short general questions...
Yes - I know about RMS possibility in Audio library .
I try to get waveform average value. I take a while to go through Audio analyze_rms.cpp and dspinst.h files but cannot understand how to sum samples from audioblocks (for later dividing by 128). Probably it's possible to include some part of code to read average.
The closest (I think so) are function:
// computes (((a[31:16] + b[31:16]) << 16) | (a[15:0 + b[15:0])) (saturates)
static inline uint32_t signed_add_16_and_16(uint32_t a, uint32_t b) __attribute__((always_inline, unused));
static inline uint32_t signed_add_16_and_16(uint32_t a, uint32_t b)
{
int32_t out;
asm volatile("qadd16 %0, %1, %2" : "=r" (out) : "r" (a), "r" (b));
return out;
}
I try to test but figures I get aren't correct.
So - that idea aren't right...
And then I stuck due to my weak programming knowledge and experience...

 

[PaulStoffregen]

Don't use the dspinst.h stuff on your first attempt! Write your first try the simplest way, even if inefficient, even if you have to use floating point math. Get that working well before you try to optimize.

For average value, you can probably just create a 32 bit variable and add all the 16 bit samples to it. Maybe check if the number is negative before adding, if you want to average to be the average of the magnitude.

 

[PeterAP]

Don't use the dspinst.h stuff on your first attempt! Write your first try the simplest way, even if inefficient, even if you have to use floating point math. Get that working well before you try to optimize.

For average value, you can probably just create a 32 bit variable and add all the 16 bit samples to it. Maybe check if the number is negative before adding, if you want to average to be the average of the magnitude.

Well I follow to advice, change analyze-rms.cpp in a bit and add "float readAvr(void);" to analyze-rms.h.
I'm always on Teensy 3 so I just exclude #else and define new variables (text in Italics).
Now result is I have expected - average of samples value.

But I'm sure that isn't optimal code...
Below are changed analyze-rms.cpp

void AudioAnalyzeRMS::update(void)
{
audio_block_t *block = receiveReadOnly();
if (!block) {
count++;
return;
}
#if defined(KINETISK)
uint32_t *p = (uint32_t *)(block->data);
uint32_t *end = p + AUDIO_BLOCK_SAMPLES/2;
int64_t sum = accum;
do {
uint32_t n1 = *p++;
uint32_t n2 = *p++;
uint32_t n3 = *p++;
uint32_t n4 = *p++;
sum = multiply_accumulate_16tx16t_add_16bx16b(sum, n1, n1);
sum = multiply_accumulate_16tx16t_add_16bx16b(sum, n2, n2);
sum = multiply_accumulate_16tx16t_add_16bx16b(sum, n3, n3);
sum = multiply_accumulate_16tx16t_add_16bx16b(sum, n4, n4);
} while (p < end);
accum = sum;
count++;
//#else
int16_t *q = block->data;
int16_t *fin = q + AUDIO_BLOCK_SAMPLES;
int64_t sumA = accumA;
do {
int32_t nA = *q++;
sumA += nA;
} while (q < fin);
accumA = sumA;
countA++;
#endif
release(block);
}

float AudioAnalyzeRMS::read(void)
{
__disable_irq();
int64_t sum = accum;
accum = 0;
uint32_t num = count;
count = 0;
__enable_irq();
float meansq = sum / (num * AUDIO_BLOCK_SAMPLES);
return sqrtf(meansq) / 32767.0;
}

float AudioAnalyzeRMS::readAvr(void)
{
__disable_irq();
int64_t sumA = accumA;
accumA = 0;
uint32_t numA = countA;
countA = 0;
__enable_irq();
float average = sumA / (numA * AUDIO_BLOCK_SAMPLES);
return average / 32767.0;
}