Audio on different channels (AUD-3128)

[mparker-landt]

Hi,

Does anyone know if it is possible to play different audio on the left/right channels of one of the I2S on ESP32 ADF.

E.g Track 1 on I2S0 channel right Track 2 on I2S0 channel left

If it is what is the best example project to use as a template?

Thanks for any help on this matter.

[HengYongChao]

Hi @mparker-landt ESP32 has two I2S peripheral interfaces, so your application can be done in principle.

[mparker-landt]

Hi @HengYongChao

Thanks for getting back to me. I know the Esp32 has 2 I2S but I would like to have three different mono tracks playing. I've been trying to get one I2S playing different tracks on the left and right channels, is this possible?

[HengYongChao]

Hi @mparker-landt Why not try downmix pipeline process? And it only use one I2S interface, also can mix up to 8 channel wav format tracks to play.

[mparker-landt]

So that's the method I'm trying, I've got the downmixer playing two tracks at the same time but they're being played on both left and right channels instead of track 1 on left and track 2 on the right channel. I've tried processing the audio by using audio_element in the pipeline registration and having the process functions go to a function.

E.g for the left channel ` static int audio_lc_process(audio_element_handle_t self, char* buf, int len, bool tag) { int rsize = audio_element_input(self, buf, len);

if (len != rsize || (rsize % 4) != 0) 
{
    ESP_LOGW(TAG, "unexpected rsize: %d, len: %d", rsize, len);
}

int16_t lSample, rSample;
char* lSamplep = (char*) &lSample;
char* rSamplep = (char*) &rSample;
for (int i = 0; i < rsize; i += 4) 
{
    rSamplep[0] = 0;
    rSamplep[1] = 0;

    lSamplep[0] = buf[i + 2];
    lSamplep[1] = buf[i + 3];

    float a = convertToF32(rSample);
    a *= 0.5;
    rSample = convertToInt16(a);

    buf[i] = 0;
    buf[i + 1] = 0;

    buf[i + 2] = lSamplep[0];
    buf[i + 3] = lSamplep[1];
}

rsize = audio_element_output(self, buf, rsize);
return rsize;

} ` However the downmixer is still playing this on both channels and I only want it on the left.

[HengYongChao]

When outputting i2s stream, you just set to output one channel only.

[mparker-landt]

How do I do that? I've tried changing .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT in the I2S config and tried changing the function downmix_set_out_ctx_info(downmixer, ESP_DOWNMIX_OUT_CTX_NORMAL); between all the left and right options and nothing seems to work. It always plays on both channels.

[jason-mao]

This topic has become inactive so I'm going to close the issue. Please reopen this if you have any questions or need any further assistance.