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The peak meter on iRiver didn't look right to me and the code seemed to be

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making it a lot more complicated that it needed to be, so I threw in some new
code. This should be easy to adjust for different CPU loads, and I set it up
to use a little less than what was there. If this causes any trouble, please
roll it back.


git-svn-id: svn://svn.rockbox.org/rockbox/trunk@7238 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Dave Bryant 2005-07-25 05:50:47 +00:00
parent c5ebc8e4e4
commit 27c83252e2
1 changed files with 58 additions and 77 deletions
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135
firmware/pcm_playback.c
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@ -89,87 +89,68 @@ static void dma_stop(void)
pcm_paused = false;
}
#define PEEK_SAMPLE_COUNT 64
static long calculate_channel_peak_average(int channel, unsigned short *addr,
long size)
{
int i;
long min, max;
int count, min_count, max_count;
unsigned long average, zero_point;
/*
* This function goes directly into the DMA buffer to calculate the left and
* right peak values. To avoid missing peaks it tries to look forward a full
* refresh period (1/20 sec) although it's always possible that the entire
* period will not be visible. To reduce CPU load it only looks at every
* third sample, and this can be reduced even further if needed (even every
* tenth sample would still be pretty accurate).
*/
addr = &addr[channel];
average = 0;
if (pcm_playing && !pcm_paused && addr != NULL && size)
{
/* Calculate the zero point and remove DC offset (should be around 32768) */
zero_point = 0;
for (i = 0; i < size; i++)
zero_point += addr[i*2];
zero_point /= i;
/*for (i = 0; i < size; i++) {
long peak = addr[i*2] - 32768;
if (peak < 0)
peak = 0;
average += peak;
}
average /= i;*/
count = 0;
while (size > PEEK_SAMPLE_COUNT)
{
min = zero_point;
max = zero_point;
min_count = 1;
max_count = 1;
for (i = 0; i < PEEK_SAMPLE_COUNT; i++)
{
unsigned long value = *addr;
if (value < zero_point) {
min += value;
min_count++;
}
if (value > zero_point) {
max += value;
max_count++;
}
addr = &addr[2];
}
min /= min_count;
max /= max_count;
size -= PEEK_SAMPLE_COUNT;
average += (max - min) / 2;
//average += (max - zero_point) + (zero_point - min);
//average += zero_point - min;
count += 1;
}
if (count)
{
average /= count;
/* I don't know why this is needed. Should be fixed. */
average = zero_point - average;
}
}
return average;
}
#define PEAK_SAMPLES 2205 /* 44100 sample rate / 20 Hz refresh */
#define PEAK_STRIDE 3 /* every 3rd sample is plenty... */
void pcm_calculate_peaks(int *left, int *right)
{
unsigned short *addr = (unsigned short *)SAR0;
long size = MIN(512, (BCR0 & 0xffffff) / 2);
if (left != NULL)
*left = calculate_channel_peak_average(0, addr, size);
if (right != NULL)
*right = calculate_channel_peak_average(1, addr, size);;
long samples = (BCR0 & 0xffffff) / 4;
short *addr = (short *) (SAR0 & ~3);
if (samples > PEAK_SAMPLES)
samples = PEAK_SAMPLES;
samples /= PEAK_STRIDE;
if (left && right) {
int left_peak = 0, right_peak = 0, value;
while (samples--) {
if ((value = addr [0]) > left_peak)
left_peak = value;
else if (-value > left_peak)
left_peak = -value;
if ((value = addr [PEAK_STRIDE | 1]) > right_peak)
right_peak = value;
else if (-value > right_peak)
right_peak = -value;
addr += PEAK_STRIDE * 2;
}
*left = left_peak;
*right = right_peak;
}
else if (left || right) {
int peak_value = 0, value;
if (right)
addr += (PEAK_STRIDE | 1);
while (samples--) {
if ((value = addr [0]) > peak_value)
peak_value = value;
else if (-value > peak_value)
peak_value = -value;
addr += PEAK_STRIDE * 2;
}
if (left)
*left = peak_value;
else
*right = peak_value;
}
}
/* sets frequency of input to DAC */