supporting of different bits per sample

[tedhsieh1966]

In https://github.com/espressif/esp-idf/blob/master/components/driver/include/driver/i2s.h , there are different type of bit width per sample supported as following.
/**

• @brief I2S bit width per sample.

/
typedef enum {
I2S_BITS_PER_SAMPLE_8BIT = 8, /!< I2S bits per sample: 8-bits*/
I2S_BITS_PER_SAMPLE_16BIT = 16, /!< I2S bits per sample: 16-bits/
I2S_BITS_PER_SAMPLE_24BIT = 24, /!< I2S bits per sample: 24-bits/
I2S_BITS_PER_SAMPLE_32BIT = 32, /!< I2S bits per sample: 32-bits/
} i2s_bits_per_sample_t;

However, in Arduino/cores/esp8266/i2s.h there is no description on how to use these.

Is there supporting of these bits_per_sample from cores for esp8266?
If yes, where can I find the usage documentation or examples?
If no, will there be a schedule to support them?

Thanks for any replying.

[earlephilhower]

Not supported now, with no expectation of adding them in. Never seen an 8-bit-only I2S DAC (thankfully!).

All the API and calls now are assuming packed 16-bits, as well as assumptions about clocking setup (reverse-engineered by multiple people) and other parts (DMA clocking/etc).

What's the use case? Never had a request from the folks using my I2S decoder library, so I'm curious...

[tedhsieh1966]

Thanks for replying. There are hifi audio with 96k, 192k and 384k sampling rate and 24bis or 32 bits per sample.

[devyte]

@earlephilhower is this request valid? Is it something you'd consider as an enhancement for your audio lib?

[earlephilhower]

It's definitely possible, but would require a significant change to the userspace API. The actual DMA/etc. doesn't care as long as you set the I2S config appropriately. Given that the I2S clocking is also only approximate (check the code that tries to figure out the closest divisor combination for the clock), hifi DACs and the 8266 seem like a waste.

24- and 32-bit samples would be handled the same, as 4-bytes per sample, left-aligned signed fractional.

Fine for leaving it open as a 3.0 or something, but probably not 2.6.x.

[devyte]

I'll leave it without a milestone for now.

[tedhsieh1966]

Hi
I had modified your code and try to run it on ESP8266 seeming without problem. I am waiting for my hardware with DAC built to test whether it really works.

if you got time, I can send you the modified code for your review.

The modified i2s.h is as following:

#define I2S_DUAL_CHANNELS (0)
#define I2S_RIGHT_CHANNEL (1)
#define I2S_LEFT_CHANNEL (2)
#define I2S_RIGHT_CHANNEL_ONLY (3)
#define I2S_LEFT_CHANNEL_ONLY (4)

#define I2STX_16BITS_FULL (0)
#define I2STX_16BITS_HALF (1)
#define I2STX_24BITS_FULL_BREAK (2)
#define I2STX_24BITS_HALF_BREAK (3)
#define I2STX_24BITS_FULL (4)
#define I2STX_24BITS_HALF (5)
#define I2SRX_16BITS_FULL (0)
#define I2SRX_16BITS_HALF (1)
#define I2SRX_24BITS_FULL_BREAK (2)
#define I2SRX_24BITS_HALF_BREAK (3)

#ifdef __cplusplus
extern "C" {
#endif

void i2s_begin(); // Enable TX only, for compatibility
bool i2s_rxtx_begin(bool enableRx, bool enableTx); // Allow TX and/or RX, returns false on OOM error
void i2s_end();
void i2s_set_rate(uint32_t rate);//Sample Rate in Hz (ex 44100, 48000)
void i2s_set_dividers(uint8_t div1, uint8_t div2);//Direct control over output rate
float i2s_get_real_rate();//The actual Sample Rate on output

/*
bool i2s_write_sample(uint32_t sample);//32bit sample with channels being upper and lower 16 bits (blocking when DMA is full)
bool i2s_write_sample_nb(uint32_t sample);//same as above but does not block when DMA is full and returns false instead
bool i2s_write_lr(int16_t left, int16_t right);//combines both channels and calls i2s_write_sample with the result
bool i2s_read_sample(int16_t *left, int16_t *right, bool blocking); // RX data returned in both 16-bit outputs.
*/
bool i2s_write_sample_lr(uint8_t *left, uint8_t *right);
bool i2s_write_frame(uint8_t *frame);
bool i2s_read_sample(int8_t *left, int8_t *right, bool blocking);
void i2s_set_sampling_rate(int sampling_rate);
void i2s_set_tx_bits_per_sample(uint8_t bits_per_sample);
void i2s_set_rx_bits_per_sample(uint8_t bits_per_sample);
void i2s_set_tx_channels(uint8_t channels);
void i2s_set_rx_channels(uint8_t channels);

bool i2s_is_full();//returns true if DMA is full and can not take more bytes (overflow)
bool i2s_is_empty();//returns true if DMA is empty (underflow)
bool i2s_rx_is_full();
bool i2s_rx_is_empty();
int16_t i2s_available();// returns the number of samples than can be written before blocking
int16_t i2s_rx_available();// returns the number of samples than can be written before blocking
void i2s_set_callback(void (*callback) (void));
void i2s_rx_set_callback(void (*callback) (void));

#ifdef __cplusplus
}
#endif

[maxmeli123]

Hi @earlephilhower I am very interested to this too, I developed an ESP8266 and ESP32 audio library like your good ESP8266Audio library, but simpler and a bit different, ESP32 have this by filling i2s configuration structures but I cannot figure how to set highter bit rates on ESP8266, without these ESP8266 cannot be used as Hi Fidelity audio player, I only can play with 16Bit audio and not with professional 24Bit and 32Bit audio for studio recording. Please, tell me if there are plains to add it or maybe point me on the right direction. Hi @tedhsieh1966 do you you tried your modified code? Many thanks to both