HOW TO CONVERT SGTL5000 DATA INTO WAV FILE?

RE: HOW TO CONVERT SGTL5000 DATA INTO WAV FILE?

Jørgen Holmefjord — Thu, 08 Apr 2021 15:31:04 GMT

Hard to say for me by just looking at your code if this is correct or not. Did you test it together with the device? Did you encounter any issues?

RE: HOW TO CONVERT SGTL5000 DATA INTO WAV FILE?

Dipak — Fri, 26 Mar 2021 17:10:15 GMT

HellO,

Thanks for the reply!

Here is the my I2S setting .

//@@@@@@ I2S setting @@@@@@@@@@@@@@@@@@@

#define AUDIO_FRAME_WORDS 320
#define I2S_BUFFER_SIZE_WORDS AUDIO_FRAME_WORDS * 2 // Double buffered - I2S lib will switch between using first and second half
static uint32_t m_i2s_tx_buffer[I2S_BUFFER_SIZE_WORDS];
static uint32_t m_i2s_rx_buffer[I2S_BUFFER_SIZE_WORDS];

/* Include car sample to demonstrate that sample can be played from application as well */
#define SAMPLE_LEN 67200
extern const uint8_t car_sample[SAMPLE_LEN];
static uint8_t * p_sample = (uint8_t *)car_sample;
static uint32_t sample_idx = 0;

int16_t data_audio[(AUDIO_FRAME_WORDS/2)];

//@@@@@@@@@@@@@@@@@@@@@@@@@@

//@@@@@@@@@@@@@@ i2c event handler @@@@@@@@@@@@@@@@@

static bool i2s_sgtl5000_driver_evt_handler(drv_sgtl5000_evt_t * p_evt)
{
bool ret = false;
//NRF_LOG_INFO("i2s_sgtl5000_driver_evt_handler %d", p_evt->evt);

//NRF_LOG_INFO("%d",p_evt->param.rx_buf_received.p_data_received);
switch (p_evt->evt)
{
case DRV_SGTL5000_EVT_I2S_RX_BUF_RECEIVED:
{

uint16_t * p_buffer = (uint16_t *) p_evt->param.rx_buf_received.p_data_received;
i2s_buffer_size_words = p_evt->param.rx_buf_received.number_of_words;
int16_t pcm_stream[i2s_buffer_size_words]; // int16_t - i2s_buffer_size_words size; means we only cover half of data_to_send_buffer, which is fine since we are only using LEFT channel

memcpy(data_audio, p_buffer, i2s_buffer_size_words);

ret = true;
}
break;
case DRV_SGTL5000_EVT_I2S_TX_BUF_REQ:
{
//NRF_LOG_INFO("i2s_sgtl5000_driver_evt_handler TX BUF REQ");

/* Play sample! 16kHz sample played on 32kHz frequency! If frequency is changed, this approach needs to change. */
/* Playback of this 16kHz sample depends on I2S MCK, RATIO, Alignment, format, and channels! Needs to be DIV8, RATIO 128X, alignment LEFT, format I2S, channels LEFT. */

uint16_t * p_buffer = (uint16_t *) p_evt->param.tx_buf_req.p_data_to_send;
uint32_t i2s_buffer_size_words = p_evt->param.rx_buf_received.number_of_words;
int16_t pcm_stream[i2s_buffer_size_words]; // int16_t - i2s_buffer_size_words size; means we only cover half of data_to_send_buffer, which is fine since we are only using LEFT channel

/* Clear pcm buffer */
memset(pcm_stream, 0, sizeof(pcm_stream));

/* Check if playing the next part of the sample will exceed the sample size, if not, copy over part of sample to be played */
if (sample_idx < SAMPLE_LEN)
{
/* Copy sample bytes into pcm_stream (or remaining part of sample). This should fill up half the actual I2S transmit buffer. */
/* We only want half becuase the sample is a 16kHz sample, and we are running the SGTL500 at 32kHz; see DRV_SGTL5000_FS_31250HZ */
uint32_t bytes_to_copy = ((sample_idx + sizeof(pcm_stream)) < SAMPLE_LEN) ? sizeof(pcm_stream) : SAMPLE_LEN - sample_idx - 1;
memcpy(pcm_stream, &p_sample[sample_idx], bytes_to_copy);
sample_idx += bytes_to_copy;
ret = true;
}
else
{
/* End of buffer reached. */
sample_idx = 0;
ret = false;
}

/* Upsample the decompressed audio */
/* i < i2s_buffer_size_words * 2 because we have a uint16_t buffer pointer */
for (int i = 0, pcm_stream_idx = 0; i < i2s_buffer_size_words * 2; i += 2)
{
for (int j = i; j < (i + 2); ++j)
{
p_buffer[j] = pcm_stream[pcm_stream_idx];

}
++pcm_stream_idx;
}

}
break;
}

return ret;
}

//@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

//@@@@@@@@@@@@@@ Here I am logging the my audio data @@@@@@@@@@@

// Enter main loop.
for (;;)
{
idle_state_handle();

for(int i = 0; i < (AUDIO_FRAME_WORDS / 2) ; i++)
{
NRF_LOG_RAW_INFO("%d\n,",data_audio[i]);

NRF_LOG_FLUSH();
}

}//FOR LOOP CLOSED BRACKET
}//MAIN LOOP CLOSED BRACKET

Please let me know the right settings for getting audio data.

RE: HOW TO CONVERT SGTL5000 DATA INTO WAV FILE?

Jørgen Holmefjord — Wed, 24 Mar 2021 13:55:19 GMT

Hi,

I spoke with our developers that made the Python script to convert the WAV file to C in the GitHub repository. They recommend using the built in package "wave" in Python to convert from PCM array to WAV, for instance like this:

import wave

# Raw uint8 values
pcm = [0x01, 0x02, etc.]

# Assume 1 channel, 16-bits (2 bytes), 16 kHz 
# w = open("my_file.wav", "wb")
w.setparams((1, 2, 16000, len(pcm)/2, 'NONE', 'not compressed'))
w.writeframes(bytes(pcm))
w.close()

This should likely work with the endianness used by nRF52 without any explicit converting, but if not, you just needs to re-arrange the bytes in the pcm-array:

pcm = [0x01, 0x02, 0x03, 0x04]

to:

pcm = [0x02, 0x01, 0x04, 0x03]

Best regards,
Jørgen

RE: HOW TO CONVERT SGTL5000 DATA INTO WAV FILE?

Dipak — Fri, 19 Mar 2021 16:59:02 GMT

If this file format is not right then please let me know how to generate the right file format for .wav file

RE: HOW TO CONVERT SGTL5000 DATA INTO WAV FILE?

Dipak — Fri, 19 Mar 2021 16:55:11 GMT

drive.google.com/.../1Ql2ESePjcKGEIsD5IySIavImhO1Mqe2jThanks for the reply!

Actually, I already used this example in my customize code but I don't know how to convert integer data into a .wav file

I have spent lots of time behind this but still, I have not got success!

I have attached the recorded data file please let me know if is it the right file for .wav conversion or not?

Please help me out with this

Thanks!

RE: HOW TO CONVERT SGTL5000 DATA INTO WAV FILE?

Jørgen Holmefjord — Tue, 16 Mar 2021 20:45:24 GMT

Hi,

This repository may provide some useful tips and links.

I'm not aware of any specific libraries for converting to WAV format, but as far as I can see, the input from SGTL5000 is PCM format, so any PCM to WAV converters should do the job.

Best regards,
Jørgen