TI DIR9001 IC implementations confusion

[HostXnine]

Hello!

first off thank you for all the great help so far.

I have a TV with only one audio output which is using Toslink. I've bought a board for converting SPDIF to I2S which uses the TI DIR9001 IC to do the conversion (link below). The board is set to use the PLL to recover the clock of input signal from the SPDIF and thus doesn't need an external crystal for MCLK. What is confusing and counter intuitive is that in the TI datasheet (link below) described that the IC outputs to I2S only a 24 bit rate signal (another option is 16 bit justified signal). I've tried different settings for the AudioInfo class but 24 bit wasn't working. What works is using 32-bit. I'm asking if there is a problem within a library (which I doubt), my understanding of audio or they use a fake IC or something which would be weird as well...

Datasheet for TI DIR9001
TI DIR9001 website
SPDIF to I2S converter board

Here is an example code that works with this board (it might work as well using RXTX mode):

#include <AudioConfig.h>
#include <AudioLogger.h>
#include <AudioTools.h>

//Audio OUT
#define I2S_WS_PIN 15 //aka LRCLK
#define I2S_BCK_PIN 14 //aka SCK
#define I2S_DATA_PIN 18 // data out

//Audio IN
#define IN_I2S_WS_PIN 34 //aka LRCLK
#define IN_I2S_BCK_PIN 25 //aka SCK
#define IN_I2S_DATA_PIN 35 // data out in

//Stream and quality
AudioInfo info(48000, 2, 32);
I2SStream i2sIn;
I2SStream i2sOut;

StreamCopy copierInOut(i2sOut, i2sIn);

void setup() {
   //I2S in
  auto cfgIn = i2sIn.defaultConfig(RX_MODE);
  cfgIn.copyFrom(info);
  cfgIn.i2s_format = I2S_STD_FORMAT;
  cfgIn.is_master = false;
  cfgIn.port_no = 0;
  cfgIn.pin_ws = IN_I2S_WS_PIN;
  cfgIn.pin_bck = IN_I2S_BCK_PIN;
  cfgIn.pin_data = IN_I2S_DATA_PIN;
  i2sIn.begin(cfgIn);

  // I2S out
  auto cfgOut = i2sOut.defaultConfig(TX_MODE);
  cfgOut.copyFrom(info); 
  cfgOut.i2s_format = I2S_STD_FORMAT;
  cfgOut.is_master = true;
  cfgOut.port_no = 1;
  cfgOut.pin_ws = I2S_WS_PIN;
  cfgOut.pin_bck = I2S_BCK_PIN;
  cfgOut.pin_data = I2S_DATA_PIN;
  i2sOut.begin(cfgOut); 
}

void loop() {
  copierInOut.copy();
}

[pschatzmann]

I think you just forgot to set the right i2s_format in the sketch.
32 bits is working because 24 bits are represented by int32_t