Keep Opus PCM little-endian on big-endian hosts

cmake/host.cmake

@@ -68,7 +68,7 @@ function(sendspin_configure_host TARGET_LIB SOURCE_DIR)
         FetchContent_Declare(
             micro_flac
             GIT_REPOSITORY https://github.com/esphome-libs/micro-flac.git
-            GIT_TAG        v0.1.1
+            GIT_TAG        v0.3.0
             GIT_SUBMODULES "lib/micro-ogg-demuxer"
         )
         FetchContent_MakeAvailable(micro_flac)

docs/integration-guide.md

@@ -230,7 +230,7 @@ the other is `SendspinNetworkProvider::is_network_ready()`.
 
 ```cpp
 struct MyPlayerListener : PlayerRoleListener {
-    // REQUIRED: Write decoded PCM audio to your audio output.
+    // REQUIRED: Write decoded PCM audio (interleaved, little-endian) to your audio output.
     // Called from a background thread. May block up to timeout_ms.
     // Must return the number of bytes actually written.
     size_t on_audio_write(uint8_t* data, size_t length, uint32_t timeout_ms) override {

include/sendspin/player_role.h

@@ -81,7 +81,7 @@ class PlayerRoleListener {
     /// @brief Writes decoded PCM audio to the platform's audio output
     ///
     /// Fires on the sync task's background thread. May block up to timeout_ms.
-    /// @param data Pointer to the decoded PCM audio data
+    /// @param data Decoded PCM audio data, interleaved and little-endian
     /// @param length Number of bytes to write; always a whole number of PCM frames
     /// @param timeout_ms Maximum time to wait for the write to complete
     /// @return Number of bytes actually written. Partial writes are allowed but must be a

src/decoder.cpp

@@ -15,6 +15,7 @@
 #include "decoder.h"
 
 #include "opus_state_location.h"
+#include "pcm_byte_order.h"
 #include "platform/logging.h"
 
 #include <algorithm>
@@ -197,6 +198,7 @@ bool SendspinDecoder::decode_audio_chunk(const uint8_t* data, size_t data_size,
         }
         *consumed = data_size;
         *decoded_size = this->current_stream_info_.frames_to_bytes(output_frames);
+        pcm16_le_to_from_host(output_buffer, *decoded_size);
 #endif
     } else {
         return false;

src/pcm_byte_order.h

@@ -0,0 +1,38 @@
+// Copyright 2026 Sendspin Contributors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// @file pcm_byte_order.h
+/// @brief Converts 16-bit PCM between the library's little-endian buffers and host order
+
+#pragma once
+
+#include <bit>
+#include <cstddef>
+#include <cstdint>
+#include <utility>
+
+namespace sendspin {
+
+/// @brief Converts 16-bit samples between little-endian and host byte order, in place
+/// @param data Sample buffer; needs no alignment
+/// @param size Buffer size in bytes
+inline void pcm16_le_to_from_host(uint8_t* data, size_t size) {
+    if constexpr (std::endian::native == std::endian::big) {
+        for (size_t i = 0; i + 1 < size; i += 2) {
+            std::swap(data[i], data[i + 1]);
+        }
+    }
+}
+
+}  // namespace sendspin

src/source_encoder_opus.cpp

@@ -15,6 +15,7 @@
 #include "source_encoder_opus.h"
 
 #include "opus_state_location.h"
+#include "pcm_byte_order.h"
 #include "platform/logging.h"
 #include "source_task.h"
 #include <opus.h>
@@ -87,6 +88,7 @@ size_t OpusSourceEncoder::encode(const uint8_t* in, size_t in_len, uint8_t* out,
     if (in != this->pcm_scratch_.data()) {
         std::memcpy(this->pcm_scratch_.data(), in, in_len);
     }
+    pcm16_le_to_from_host(this->pcm_scratch_.data(), in_len);
     // max_data_bytes is a hard packet cap: libopus lowers quality to fit rather than failing.
     // The task offers at least MAX_PACKET_BYTES, so its chunks never degrade.
     const auto capacity =