i2s_audio_spdif.cpp

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#include "i2s_audio_spdif.h"
 
#if defined(USE_ESP32) && defined(USE_I2S_AUDIO_SPDIF_MODE)
 
#include <driver/i2s_std.h>
 
#include "esphome/components/audio/audio.h"
#include "esphome/components/audio/audio_transfer_buffer.h"
 
#include "esphome/core/hal.h"
#include "esphome/core/log.h"
 
#include "esp_timer.h"
 
namespace esphome::i2s_audio {
 
ESPHOME_LOG_TAG(TAG, "i2s_audio.spdif");
 
// SPDIF mode adds overhead as each sample is encapsulated in a subframe;
// each DMA buffer can hold only 192 samples (~4ms each vs. ~15ms for standard I2S).
// To match the standard I2S buffering duration, we use more buffers to minimize
// the impact of the overhead, such as stuttering or audio/silence oscillation.
// 15 buffers x 4ms = 60ms of DMA buffering (same as 4 x 15ms for standard)
static constexpr size_t SPDIF_DMA_BUFFERS_COUNT = 15;
 
// Number of DMA events between upstream callbacks (~16ms = 4 events x 4ms each).
// Matches non-SPDIF timing to prevent overwhelming upstream sync algorithms.
static constexpr uint32_t SPDIF_DMA_EVENTS_PER_CALLBACK = 4;
 
// Brief retry wait used by play() to catch short free-space windows during rapid track transitions.
static constexpr uint32_t SPDIF_PLAY_RETRY_WAIT_MS = 5;
 
static constexpr size_t SPDIF_I2S_EVENT_QUEUE_COUNT = 2 * SPDIF_DMA_BUFFERS_COUNT;
 
// Static callback functions for SPDIF encoder (avoids std::function overhead)
static esp_err_t spdif_preload_cb(void *user_ctx, uint32_t *data, size_t size, TickType_t ticks_to_wait) {
  auto *speaker = static_cast<I2SAudioSpeakerSPDIF *>(user_ctx);
  size_t bytes_written = 0;
  esp_err_t err = i2s_channel_preload_data(speaker->get_tx_handle(), data, size, &bytes_written);
  if (err != ESP_OK || bytes_written != size) {
    ESP_LOGV(TAG, "Preload failed: %s (wrote %zu/%zu bytes)", esp_err_to_name(err), bytes_written, size);
    return (err != ESP_OK) ? err : ESP_ERR_NO_MEM;
  }
  return ESP_OK;
}
 
static esp_err_t spdif_write_cb(void *user_ctx, uint32_t *data, size_t size, TickType_t ticks_to_wait) {
  auto *speaker = static_cast<I2SAudioSpeakerSPDIF *>(user_ctx);
  size_t bytes_written = 0;
  esp_err_t err = i2s_channel_write(speaker->get_tx_handle(), data, size, &bytes_written, ticks_to_wait);
  if (err != ESP_OK || bytes_written != size) {
    ESP_LOGV(TAG, "I2S write failed: %s (wrote %zu/%zu bytes)", esp_err_to_name(err), bytes_written, size);
    return (err != ESP_OK) ? err : ESP_FAIL;
  }
  return ESP_OK;
}
 
void I2SAudioSpeakerSPDIF::setup() {
  I2SAudioSpeakerBase::setup();
  if (this->is_failed()) {
    return;
  }
 
  this->spdif_encoder_ = new SPDIFEncoder();
  if (!this->spdif_encoder_->setup()) {
    ESP_LOGE(TAG, "Encoder setup failed");
    this->mark_failed();
    return;
  }
 
  // Configure channel status block with the sample rate
  this->spdif_encoder_->set_sample_rate(this->sample_rate_);
 
  // Separate callbacks for preload (during underflow recovery) and normal writes
  this->spdif_encoder_->set_preload_callback(spdif_preload_cb, this);
  this->spdif_encoder_->set_write_callback(spdif_write_cb, this);
}
 
void I2SAudioSpeakerSPDIF::dump_config() {
  I2SAudioSpeakerBase::dump_config();
  ESP_LOGCONFIG(TAG,
                "  SPDIF Mode: YES\n"
                "  Sample Rate: %" PRIu32 " Hz",
                this->sample_rate_);
}
 
void I2SAudioSpeakerSPDIF::on_task_stopped() { this->spdif_silence_start_ = 0; }
 
size_t I2SAudioSpeakerSPDIF::play(const uint8_t *data, size_t length, TickType_t ticks_to_wait) {
  if (this->is_failed()) {
    ESP_LOGE(TAG, "Setup failed; cannot play audio");
    return 0;
  }
 
  // In SPDIF mode, keep accepting upstream audio while the speaker task is active.
  // This avoids transient drops during stop/start transitions.
  const bool task_active = (this->speaker_task_handle_ != nullptr);
 
  if (this->state_ != speaker::STATE_RUNNING && this->state_ != speaker::STATE_STARTING) {
    this->start();
  }
 
  if (!task_active && this->state_ != speaker::STATE_RUNNING) {
    // Unable to write data to a running speaker, so delay the max amount of time so it can get ready
    vTaskDelay(ticks_to_wait);
    ticks_to_wait = 0;
  }
 
  size_t bytes_written = 0;
  if (this->state_ == speaker::STATE_RUNNING || task_active) {
    std::shared_ptr<ring_buffer::RingBuffer> temp_ring_buffer = this->audio_ring_buffer_.lock();
    if (temp_ring_buffer != nullptr) {
      // In SPDIF mode, a tiny wait helps avoid transient 0-byte writes during short backpressure windows.
      TickType_t effective_ticks_to_wait = ticks_to_wait;
      if (effective_ticks_to_wait == 0) {
        effective_ticks_to_wait = pdMS_TO_TICKS(1);
      }
      bytes_written = temp_ring_buffer->write_without_replacement((void *) data, length, effective_ticks_to_wait);
      if (bytes_written == 0 && length > 0) {
        // Retry once to catch short free-space windows during rapid seek/track transitions.
        bytes_written =
            temp_ring_buffer->write_without_replacement((void *) data, length, pdMS_TO_TICKS(SPDIF_PLAY_RETRY_WAIT_MS));
      }
    }
  }
 
  return bytes_written;
}
 
void I2SAudioSpeakerSPDIF::run_speaker_task() {
  xEventGroupSetBits(this->event_group_, SpeakerEventGroupBits::TASK_STARTING);
 
  // Reset SPDIF encoder at task start to ensure clean state
  // (previous task may have left stale data in encoder buffer)
  if (this->spdif_encoder_ != nullptr) {
    this->spdif_encoder_->reset();
  }
 
  // Reset lockstep records queue so it starts paired with the (also-reset) i2s_event_queue_.
  xQueueReset(this->write_records_queue_);
 
  // The DMA buffers may have more bits per sample, so calculate buffer sizes based on the input audio stream info
  const size_t bytes_per_frame = this->current_stream_info_.frames_to_bytes(1);
 
  // For SPDIF mode, one DMA buffer = one SPDIF block = 192 PCM frames (~4 ms at 48 kHz),
  // not the ~15 ms a standard I2S DMA buffer holds. Derive the DMA floor from actual block size.
  const uint32_t frames_to_fill_single_dma_buffer = SPDIF_BLOCK_SAMPLES;
  const size_t bytes_to_fill_single_dma_buffer =
      this->current_stream_info_.frames_to_bytes(frames_to_fill_single_dma_buffer);
  const size_t dma_buffers_floor_bytes = bytes_to_fill_single_dma_buffer * SPDIF_DMA_BUFFERS_COUNT;
 
  // Round the ring buffer size down to a multiple of bytes_per_frame so the wrap boundary stays frame-aligned and
  // avoids unnecessary single-frame splices. Ensure it is at least large enough to cover all DMA buffers.
  const size_t requested_ring_buffer_bytes =
      (this->current_stream_info_.ms_to_bytes(this->buffer_duration_ms_) / bytes_per_frame) * bytes_per_frame;
  const size_t ring_buffer_size = std::max(dma_buffers_floor_bytes, requested_ring_buffer_bytes);
 
  bool successful_setup = false;
  std::unique_ptr<audio::RingBufferAudioSource> audio_source;
 
  {
    std::shared_ptr<ring_buffer::RingBuffer> temp_ring_buffer = ring_buffer::RingBuffer::create(ring_buffer_size);
    audio_source = audio::RingBufferAudioSource::create(temp_ring_buffer, bytes_to_fill_single_dma_buffer,
                                                        static_cast<uint8_t>(bytes_per_frame));
    if (audio_source != nullptr) {
      this->audio_ring_buffer_ = temp_ring_buffer;
      successful_setup = true;
    }
  }
 
  // Preload DMA buffers with SPDIF-encoded silence before enabling the channel.
  // This ensures the first data transmitted is valid SPDIF (not raw zeros from
  // auto_clear) and prevents phantom DMA events before real audio is available.
  // Each preloaded block pushes a 0-real-frame record so that the corresponding
  // on_sent events drain in lockstep without crediting any audio frames. Runs with
  // the channel disabled: at startup and after a resync.
  auto preload_silence = [&]() -> bool {
    bool ok = true;
    this->spdif_encoder_->set_preload_mode(true);
    for (size_t i = 0; i < SPDIF_DMA_BUFFERS_COUNT; i++) {
      // i2s_channel_preload_data is non-blocking (returns immediately when the preload buffer fills), so no wait.
      const uint32_t silence_record = 0;
      if ((this->spdif_encoder_->flush_with_silence(0) != ESP_OK) ||
          (xQueueSendToBack(this->write_records_queue_, &silence_record, 0) != pdTRUE)) {
        ok = false;
        break;
      }
    }
    this->spdif_encoder_->set_preload_mode(false);
    this->spdif_encoder_->reset();  // Clean encoder state for the main loop
    return ok;
  };
 
  if (successful_setup) {
    successful_setup = preload_silence();
  }
 
  if (successful_setup) {
    // Register the callback before enabling so the first transmitted block generates a queued event.
    xQueueReset(this->i2s_event_queue_);
    const i2s_event_callbacks_t callbacks = {.on_sent = i2s_on_sent_cb};
    i2s_channel_register_event_callback(this->tx_handle_, &callbacks, this);
    successful_setup = i2s_channel_enable(this->tx_handle_) == ESP_OK;
  }
 
  if (!successful_setup) {
    xEventGroupSetBits(this->event_group_, SpeakerEventGroupBits::ERR_ESP_NO_MEM);
  } else {
    // Always-fill model: each iteration produces exactly one SPDIF block (= one DMA buffer).
    // We drain real PCM up to one block from the ring buffer and silence-pad any remainder.
    // Blocking writes pace the loop at the DMA consumption rate. This mirrors the standard
    // I2S speaker pattern (PR #16317): fill what you can, then silence-pad whatever is still
    // missing to complete the DMA buffer.
    const uint32_t block_duration_us = this->current_stream_info_.frames_to_microseconds(SPDIF_BLOCK_SAMPLES);
    // Sized to absorb the worst case where every DMA buffer is full when we issue the write.
    const TickType_t write_timeout_ticks =
        pdMS_TO_TICKS(((block_duration_us * (SPDIF_DMA_BUFFERS_COUNT + 1)) + 999) / 1000);
    // Brief read budget when the ring buffer is empty (~half a block).
    const TickType_t read_timeout_ticks = pdMS_TO_TICKS(((block_duration_us / 2) + 999) / 1000);
 
    // SPDIF Callback Decimation: fire every 4th DMA event (~16ms), matching non-SPDIF timing.
    uint32_t spdif_pending_frames = 0;
    int64_t spdif_pending_timestamp = 0;
    uint32_t spdif_dma_event_count = 0;
    bool resync_needed = false;
    // Real frames consumed from the ring buffer that never reached a write record
    uint32_t unrecorded_frames = 0;
 
    xEventGroupSetBits(this->event_group_, SpeakerEventGroupBits::TASK_RUNNING);
 
    // SPDIF continuous mode: loop runs indefinitely, outputting silence when no audio data
    // to keep the receiver synced. Exits only via break (stream info change, silence timeout,
    // or a failed lockstep resync).
    while (true) {
      uint32_t event_group_bits = xEventGroupGetBits(this->event_group_);
 
      if (event_group_bits & SpeakerEventGroupBits::COMMAND_STOP) {
        xEventGroupClearBits(this->event_group_, SpeakerEventGroupBits::COMMAND_STOP);
        // User-initiated stop. In SPDIF continuous mode, transition to silence output rather
        // than tearing the task down.
        this->spdif_silence_start_ = millis();
        ESP_LOGV(TAG, "COMMAND_STOP received, continuing in silence mode");
      }
      if (event_group_bits & SpeakerEventGroupBits::COMMAND_STOP_GRACEFULLY) {
        // SPDIF continuous mode never tears the channel down on graceful stop. Clear the flag and
        // let the audio simply drain through the always-fill loop into the silence-timeout path.
        xEventGroupClearBits(this->event_group_, SpeakerEventGroupBits::COMMAND_STOP_GRACEFULLY);
      }
 
      if (this->audio_stream_info_ != this->current_stream_info_) {
        ESP_LOGV(TAG, "Exiting: stream info changed");
        break;
      }
 
      if (event_group_bits & SpeakerEventGroupBits::ERR_DROPPED_EVENT) {
        ESP_LOGE(TAG, "ISR event queue overflow, resyncing DMA lockstep");
        resync_needed = true;
      }
      if (resync_needed) {
        // Rebuild the lockstep in place. Frames held back by decimation are credited too, since their
        // blocks are discarded with the rest of the DMA contents.
        this->spdif_encoder_->reset();
        const uint32_t credited_frames = unrecorded_frames + spdif_pending_frames;
        const bool resynced = this->resync_lockstep_(credited_frames, preload_silence);
        unrecorded_frames = 0;
        spdif_pending_frames = 0;
        spdif_dma_event_count = 0;
        resync_needed = false;
        if (credited_frames > 0) {
          // Real audio was dropped, so the silence timer's start no longer reflects the stream
          this->spdif_silence_start_ = 0;
        }
        if (!resynced) {
          ESP_LOGE(TAG, "DMA lockstep resync failed, restarting speaker task");
          break;
        }
      }
 
      // Drain ISR completion events, popping a matching record for each.
      int64_t write_timestamp;
      bool lockstep_broken = false;
      while (xQueueReceive(this->i2s_event_queue_, &write_timestamp, 0)) {
        // Lockstep: pop the matching record (real audio frames packed into this DMA block).
        // Records are pushed by the task right after each successful block commit, so the FIFO
        // order matches DMA completion order. Empty records queue here means lockstep broke.
        uint32_t real_frames = 0;
        if (xQueueReceive(this->write_records_queue_, &real_frames, 0) != pdTRUE) {
          ESP_LOGE(TAG, "Event without matching write record, resyncing DMA lockstep");
          lockstep_broken = true;
          break;
        }
 
        // Per-block timestamp adjustment: shift back by the silence-padding portion of the block
        // so the reported timestamp reflects when the last real sample left the wire.
        uint32_t frames_sent = real_frames;
        if (real_frames < SPDIF_BLOCK_SAMPLES) {
          const uint32_t frames_zeroed = SPDIF_BLOCK_SAMPLES - real_frames;
          write_timestamp -= this->current_stream_info_.frames_to_microseconds(frames_zeroed);
        }
 
        spdif_dma_event_count++;
        // Accumulate frames; keep the latest timestamp so the callback reports when the last
        // sample left the wire, not the first.
        if (frames_sent > 0) {
          spdif_pending_timestamp = write_timestamp;
          spdif_pending_frames += frames_sent;
        }
 
        bool decimation_reached = (spdif_dma_event_count >= SPDIF_DMA_EVENTS_PER_CALLBACK);
        // Partial blocks mark an end-of-stream boundary (silence-padded tail). Fire immediately
        // so the back-shifted timestamp isn't overwritten by a later full audio block landing
        // in the same decimation window.
        bool partial_flush = (real_frames > 0 && real_frames < SPDIF_BLOCK_SAMPLES);
 
        if (decimation_reached || partial_flush) {
          if (spdif_pending_frames > 0) {
            this->audio_output_callback_(spdif_pending_frames, spdif_pending_timestamp);
            spdif_pending_frames = 0;
          }
          spdif_dma_event_count = 0;
        }
      }
      if (lockstep_broken) {
        resync_needed = true;
        continue;
      }
 
      // Always-fill: produce exactly one SPDIF block this iteration. The blocking encoder write
      // paces the task at the DMA consumption rate.
      uint32_t real_frames_in_block = 0;
      bool block_committed = false;
      bool partial_write_failure = false;
 
      if (!this->pause_state_) {
        while (real_frames_in_block < SPDIF_BLOCK_SAMPLES) {
          if (audio_source->available() == 0) {
            size_t bytes_read = audio_source->fill(read_timeout_ticks);
            if (bytes_read == 0) {
              break;  // No upstream data within the read budget; silence-pad the remainder.
            }
            uint8_t *new_data = audio_source->mutable_data();
            this->apply_software_volume_(new_data, bytes_read);
            this->swap_esp32_mono_samples_(new_data, bytes_read);
          }
 
          const uint32_t frames_still_needed = SPDIF_BLOCK_SAMPLES - real_frames_in_block;
          const size_t bytes_still_needed = this->current_stream_info_.frames_to_bytes(frames_still_needed);
          const size_t bytes_to_feed = std::min(audio_source->available(), bytes_still_needed);
 
          uint32_t blocks_sent = 0;
          size_t pcm_consumed = 0;
          esp_err_t err = this->spdif_encoder_->write(audio_source->data(), bytes_to_feed, write_timeout_ticks,
                                                      &blocks_sent, &pcm_consumed);
          if (err != ESP_OK) {
            // A failed (or timed-out) send leaves an unsent block in the encoder's stitch buffer;
            // resuming would credit the next iteration's bytes against an old block.
            ESP_LOGE(TAG, "SPDIF block send failed, resyncing DMA lockstep");
            partial_write_failure = true;
            break;
          }
 
          if (pcm_consumed > 0) {
            audio_source->consume(pcm_consumed);
            real_frames_in_block += this->current_stream_info_.bytes_to_frames(pcm_consumed);
          }
          if (blocks_sent > 0) {
            block_committed = true;
            break;
          }
        }
      }
 
      if (partial_write_failure) {
        unrecorded_frames += real_frames_in_block;
        resync_needed = true;
        continue;
      }
 
      if (!block_committed) {
        // Pad whatever real audio we managed to feed (if any) with silence to complete one block,
        // or emit a full silence block if the encoder is empty.
        esp_err_t err = this->spdif_encoder_->flush_with_silence(write_timeout_ticks);
        if (err != ESP_OK) {
          ESP_LOGE(TAG, "SPDIF block send failed, resyncing DMA lockstep");
          unrecorded_frames += real_frames_in_block;
          resync_needed = true;
          continue;
        }
      }
 
      // One block committed to DMA; push exactly one record carrying its real-audio frame count.
      // Failure here means the records queue is full, which violates the lockstep invariant.
      if (xQueueSendToBack(this->write_records_queue_, &real_frames_in_block, 0) != pdTRUE) {
        ESP_LOGE(TAG, "Write records queue full, resyncing DMA lockstep");
        unrecorded_frames += real_frames_in_block;
        resync_needed = true;
        continue;
      }
 
      // Silence-timeout tracking and graceful-stop reset.
      if (real_frames_in_block == 0) {
        if (this->spdif_silence_start_ == 0) {
          this->spdif_silence_start_ = millis();
        }
 
        if (this->timeout_.has_value()) {
          const uint32_t silence_duration = millis() - this->spdif_silence_start_;
          if (silence_duration >= this->timeout_.value()) {
            ESP_LOGV(TAG, "Silence timeout reached (%" PRIu32 "ms) - stopping speaker", silence_duration);
            break;
          }
        }
      } else if (this->spdif_silence_start_ != 0) {
        uint32_t silence_duration = millis() - this->spdif_silence_start_;
        if (silence_duration > 100) {
          ESP_LOGV(TAG, "Exiting silence mode after %" PRIu32 "ms, have audio data", silence_duration);
        }
        this->spdif_silence_start_ = 0;
      }
    }
  }
 
  xEventGroupSetBits(this->event_group_, SpeakerEventGroupBits::TASK_STOPPING);
 
  // Reset SPDIF encoder state to prevent stale state on next start
  if (this->spdif_encoder_ != nullptr) {
    this->spdif_encoder_->set_preload_mode(false);
    this->spdif_encoder_->reset();
  }
 
  audio_source.reset();
 
  xEventGroupSetBits(this->event_group_, SpeakerEventGroupBits::TASK_STOPPED);
 
  while (true) {
    // Continuously delay until the loop method deletes the task
    vTaskDelay(pdMS_TO_TICKS(10));
  }
}
 
esp_err_t I2SAudioSpeakerSPDIF::start_i2s_driver(audio::AudioStreamInfo &audio_stream_info) {
  this->current_stream_info_ = audio_stream_info;
  // SPDIF never narrows the bit depth; the encoder consumes the input format directly.
  this->output_stream_info_ = audio_stream_info;
 
  // SPDIF mode validation
  if (this->sample_rate_ != audio_stream_info.get_sample_rate()) {
    ESP_LOGE(TAG, "Only supports a single sample rate (configured: %" PRIu32 " Hz, stream: %" PRIu32 " Hz)",
             this->sample_rate_, audio_stream_info.get_sample_rate());
    return ESP_ERR_NOT_SUPPORTED;
  }
  const uint8_t bits_per_sample = audio_stream_info.get_bits_per_sample();
  if (bits_per_sample != 16 && bits_per_sample != 24 && bits_per_sample != 32) {
    ESP_LOGE(TAG, "Only supports 16, 24, or 32 bits per sample (got %u)", (unsigned) bits_per_sample);
    return ESP_ERR_NOT_SUPPORTED;
  }
  if (audio_stream_info.get_channels() != 2) {
    ESP_LOGE(TAG, "Only supports stereo (2 channels)");
    return ESP_ERR_NOT_SUPPORTED;
  }
 
  // Tell the encoder what input width to expect. 32-bit input is truncated to 24-bit on the wire.
  this->spdif_encoder_->set_bytes_per_sample(bits_per_sample / 8);
 
  if (!this->parent_->try_lock()) {
    ESP_LOGE(TAG, "Parent bus is busy");
    return ESP_ERR_INVALID_STATE;
  }
 
  // SPDIF mode: fixed configuration for BMC encoding
  // For new driver, dma_frame_num is in I2S frames (8 bytes each for 32-bit stereo)
  uint32_t dma_buffer_length = SPDIF_BLOCK_I2S_FRAMES;  // One SPDIF block = 384 I2S frames = 3072 bytes
 
  // Log DMA configuration for debugging
  ESP_LOGV(TAG, "I2S DMA config: %zu buffers x %lu frames = %lu bytes total", (size_t) SPDIF_DMA_BUFFERS_COUNT,
           (unsigned long) dma_buffer_length,
           (unsigned long) (SPDIF_DMA_BUFFERS_COUNT * dma_buffer_length * 8));  // 8 bytes per frame for 32-bit stereo
 
  i2s_chan_config_t chan_cfg = {
      .id = this->parent_->get_port(),
      .role = this->i2s_role_,
      .dma_desc_num = SPDIF_DMA_BUFFERS_COUNT,
      .dma_frame_num = dma_buffer_length,
      .auto_clear = true,
      .intr_priority = 3,
  };
 
  // SPDIF: double sample rate for BMC, 32-bit stereo, only data pin needed
  i2s_std_clk_config_t clk_cfg = {
      .sample_rate_hz = this->sample_rate_ * 2,
      .clk_src = this->get_clock_source_(),
      .mclk_multiple = this->mclk_multiple_,
  };
 
  i2s_std_slot_config_t slot_cfg = I2S_STD_PHILIPS_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_32BIT, I2S_SLOT_MODE_STEREO);
 
  i2s_std_gpio_config_t gpio_cfg = {
      .mclk = GPIO_NUM_NC,
      .bclk = GPIO_NUM_NC,
      .ws = GPIO_NUM_NC,
      .dout = this->dout_pin_,
      .din = GPIO_NUM_NC,
      .invert_flags =
          {
              .mclk_inv = false,
              .bclk_inv = false,
              .ws_inv = false,
          },
  };
 
  i2s_std_config_t std_cfg = {
      .clk_cfg = clk_cfg,
      .slot_cfg = slot_cfg,
      .gpio_cfg = gpio_cfg,
  };
 
  esp_err_t err = this->init_i2s_channel_(chan_cfg, std_cfg, SPDIF_I2S_EVENT_QUEUE_COUNT);
  if (err != ESP_OK) {
    return err;
  }
 
  // Channel is NOT enabled here. The speaker task will preload DMA buffers
  // with SPDIF-encoded silence before enabling, ensuring the first data on
  // the wire is valid SPDIF (not raw zeros from auto_clear) and preventing
  // phantom DMA events before real audio data is available.
 
  return ESP_OK;
}
 
}  // namespace esphome::i2s_audio
 
#endif  // USE_ESP32 && USE_I2S_AUDIO_SPDIF_MODE