forked from PAWPAW-Mirror/lib_xua
51 lines
1.2 KiB
C
51 lines
1.2 KiB
C
#include "xud.h"
|
|
|
|
extern XUD_BusSpeed_t g_curUsbSpeed;
|
|
|
|
/* Returns the max and min packet sizes to send back to host for a given sample frequency
|
|
* See page 13 of USB Audio Device Class Definitions for Audio Data Formats Spec (v2.0)
|
|
*
|
|
* Audio samples per frame = INT(sampFreq/frametime); Variation allowed is + 1;
|
|
*
|
|
* For HS frame time = 8 * 1000
|
|
*
|
|
* so n = INT(SampFreq/8000) | INT (SampFreq/8000) + 1
|
|
*
|
|
* In the case where INT(SampFreq/8000) == SampFreq/8000) n may vary between
|
|
*
|
|
* INT(SamFreq/8000) - 1 | INT(SampFreq/8000) | INT (SampFreq/8000) + 1
|
|
*
|
|
* Note: Assumes HS (i.e. 8 frames per 1ms)
|
|
*
|
|
* Examples:
|
|
* 44100: min: 5 max: 6
|
|
* 48000: min: 5 max: 7
|
|
* 96000: min: 11 max: 13
|
|
* 88200: min: 11 max: 12
|
|
* 176400: min: 22 max: 23
|
|
* 192000: min: 23 max: 25
|
|
*
|
|
*/
|
|
void GetADCCounts(unsigned samFreq, int *min, int *mid, int *max)
|
|
{
|
|
unsigned frameTime;
|
|
XUD_BusSpeed_t usb_speed;
|
|
usb_speed = g_curUsbSpeed;
|
|
if (usb_speed == XUD_SPEED_HS)
|
|
frameTime = 8000;
|
|
else
|
|
frameTime = 1000;
|
|
|
|
*min = samFreq / frameTime;
|
|
*max = *min + 1;
|
|
|
|
*mid = *min;
|
|
|
|
/* Check for INT(SampFreq/8000) == SampFreq/8000 */
|
|
if((samFreq % frameTime) == 0)
|
|
{
|
|
*min -= 1;
|
|
}
|
|
|
|
}
|