Add a class to house FLAC stream callback functions & implement the r…

…ead callback.

These are necessary to use the FLAC stream decoder.

Also adds an encoded_frame_ field in flac_decoder.h which is used to store a single encoded frame at a time for later processing. This is necessary because flac stream uses callback functions. Getters & setters are added so that the call back functions can access the data as necessary.

PiperOrigin-RevId: 686183659

iamf/cli/codec/BUILD

@@ -193,3 +193,14 @@ cc_library(
         "@com_google_absl//absl/status",
     ],
 )
+
+cc_library(
+    name = "flac_decoder_stream_callbacks",
+    srcs = ["flac_decoder_stream_callbacks.cc"],
+    hdrs = ["flac_decoder_stream_callbacks.h"],
+    deps = [
+        ":flac_decoder",
+        "@com_google_absl//absl/log",
+        "@flac//:src",
+    ],
+)

iamf/cli/codec/flac_decoder.h

@@ -41,7 +41,7 @@ class FlacDecoder : public DecoderBase {
    */
   absl::Status Initialize() override;
 
-  /*!\brief Decodes a Flac audio frame.
+  /*!\brief Decodes a FLAC audio frame.
    *
    * \param encoded_frame Frame to decode.
    * \param decoded_samples Output decoded frames arranged in (time, sample)
@@ -52,7 +52,22 @@ class FlacDecoder : public DecoderBase {
       const std::vector<uint8_t>& encoded_frame,
       std::vector<std::vector<int32_t>>& decoded_samples) override;
 
+  /*!\brief Sets an encoded FLAC frame in decoder.encoded_frame_.
+   *
+   * \param encoded_frame Encoded FLAC frame.
+   */
+  void SetEncodedFrame(const std::vector<uint8_t>& encoded_frame) {
+    encoded_frame_ = encoded_frame;
+  }
+
+  /*!\brief Retrieves the encoded frame in decoder.encoded_frame_.
+   *
+   * \return Vector of encoded FLAC bytes representing a single frame.
+   */
+  std::vector<uint8_t> GetEncodedFrame() const { return encoded_frame_; }
+
  private:
+  std::vector<uint8_t> encoded_frame_ = {};
   const FlacDecoderConfig decoder_config_;
 };
 

iamf/cli/codec/flac_decoder_stream_callbacks.cc

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2024, Alliance for Open Media. All rights reserved
+ *
+ * This source code is subject to the terms of the BSD 3-Clause Clear License
+ * and the Alliance for Open Media Patent License 1.0. If the BSD 3-Clause Clear
+ * License was not distributed with this source code in the LICENSE file, you
+ * can obtain it at www.aomedia.org/license/software-license/bsd-3-c-c. If the
+ * Alliance for Open Media Patent License 1.0 was not distributed with this
+ * source code in the PATENTS file, you can obtain it at
+ * www.aomedia.org/license/patent.
+ */
+
+#include "iamf/cli/codec/flac_decoder_stream_callbacks.h"
+
+#include <cstddef>
+
+#include "absl/log/log.h"
+#include "iamf/cli/codec/flac_decoder.h"
+#include "include/FLAC/ordinals.h"
+#include "include/FLAC/stream_decoder.h"
+
+namespace iamf_tools {
+
+FLAC__StreamDecoderReadStatus LibFlacReadCallback(
+    const FLAC__StreamDecoder* /*decoder*/, FLAC__byte buffer[], size_t* bytes,
+    void* client_data) {
+  auto flac_decoder = static_cast<FlacDecoder*>(client_data);
+  const auto& encoded_frame = flac_decoder->GetEncodedFrame();
+  if (encoded_frame.empty()) {
+    // No more data to read.
+    *bytes = 0;
+    return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM;
+  }
+  if (encoded_frame.size() > *bytes) {
+    LOG(ERROR) << "Encoded frame size " << encoded_frame.size()
+               << " is larger than the libflac buffer size " << *bytes;
+    *bytes = 0;
+    return FLAC__STREAM_DECODER_READ_STATUS_ABORT;
+  }
+  for (int i = 0; i < encoded_frame.size(); ++i) {
+    buffer[i] = encoded_frame[i];
+  }
+  *bytes = encoded_frame.size();
+  return FLAC__STREAM_DECODER_READ_STATUS_CONTINUE;
+}
+
+}  // namespace iamf_tools

iamf/cli/codec/flac_decoder_stream_callbacks.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2024, Alliance for Open Media. All rights reserved
+ *
+ * This source code is subject to the terms of the BSD 3-Clause Clear License
+ * and the Alliance for Open Media Patent License 1.0. If the BSD 3-Clause Clear
+ * License was not distributed with this source code in the LICENSE file, you
+ * can obtain it at www.aomedia.org/license/software-license/bsd-3-c-c. If the
+ * Alliance for Open Media Patent License 1.0 was not distributed with this
+ * source code in the PATENTS file, you can obtain it at
+ * www.aomedia.org/license/patent.
+ */
+
+#ifndef CLI_CODEC_FLAC_DECODER_STREAM_CALLBACKS_H_
+#define CLI_CODEC_FLAC_DECODER_STREAM_CALLBACKS_H_
+
+#include <cstddef>
+
+#include "include/FLAC/ordinals.h"
+#include "include/FLAC/stream_decoder.h"
+
+namespace iamf_tools {
+/*!\brief Reads an encoded flac frame into the libflac decoder
+ *
+ * This callback function is used whenever the decoder needs more input data.
+ *
+ * \param decoder libflac stream decoder
+ *        This parameter is not used in this implementation, but is included to
+ *        override the libflac signature.
+ * \param buffer Output buffer for the encoded frame.
+ * \param bytes Maximum size of the buffer; in the case of a successful read,
+ *        this will be set to the actual number of bytes read.
+ * \param client_data universal pointer, which in this case should point to
+ *        FlacDecoder.
+ *
+ * \return A libflac read status indicating whether the read was successful.
+ */
+FLAC__StreamDecoderReadStatus LibFlacReadCallback(
+    const FLAC__StreamDecoder* decoder, FLAC__byte buffer[], size_t* bytes,
+    void* client_data);
+
+}  // namespace iamf_tools
+
+#endif  // CLI_CODEC_FLAC_DECODER_STREAM_CALLBACKS_H_

iamf/cli/codec/tests/BUILD

@@ -116,3 +116,17 @@ cc_test(
         "@com_google_googletest//:gtest_main",
     ],
 )
+
+cc_test(
+    name = "flac_decoder_stream_callbacks_test",
+    srcs = ["flac_decoder_stream_callbacks_test.cc"],
+    deps = [
+        "//iamf/cli/codec:flac_decoder",
+        "//iamf/cli/codec:flac_decoder_stream_callbacks",
+        "//iamf/obu:codec_config",
+        "//iamf/obu:obu_header",
+        "//iamf/obu/decoder_config:flac_decoder_config",
+        "@com_google_googletest//:gtest_main",
+        "@flac//:src",
+    ],
+)

iamf/cli/codec/tests/flac_decoder_stream_callbacks_test.cc

@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2024, Alliance for Open Media. All rights reserved
+ *
+ * This source code is subject to the terms of the BSD 3-Clause Clear License
+ * and the Alliance for Open Media Patent License 1.0. If the BSD 3-Clause Clear
+ * License was not distributed with this source code in the LICENSE file, you
+ * can obtain it at www.aomedia.org/license/software-license/bsd-3-c-c. If the
+ * Alliance for Open Media Patent License 1.0 was not distributed with this
+ * source code in the PATENTS file, you can obtain it at
+ * www.aomedia.org/license/patent.
+ */
+
+#include "iamf/cli/codec/flac_decoder_stream_callbacks.h"
+
+#include <cstddef>
+#include <cstdint>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "iamf/cli/codec/flac_decoder.h"
+#include "iamf/obu/codec_config.h"
+#include "iamf/obu/decoder_config/flac_decoder_config.h"
+#include "iamf/obu/obu_header.h"
+#include "include/FLAC/ordinals.h"
+#include "include/FLAC/stream_decoder.h"
+
+namespace iamf_tools {
+namespace {
+
+using ::testing::ElementsAreArray;
+
+class FlacDecoderStreamCallbacksTest : public testing::Test {
+ public:
+  FlacDecoderStreamCallbacksTest()
+      : flac_decoder_(FlacDecoder(
+            (CodecConfigObu(ObuHeader(), 0,
+                            {.codec_id = CodecConfig::kCodecIdFlac,
+                             .num_samples_per_frame = 1024,
+                             .audio_roll_distance = -1,
+                             .decoder_config = FlacDecoderConfig{}})),
+            /*num_channels=*/2)) {}
+
+ protected:
+  FlacDecoder flac_decoder_;
+};
+
+TEST_F(FlacDecoderStreamCallbacksTest, ReadCallbackEmptyFrame) {
+  FLAC__byte buffer[1024];
+  size_t bytes = 1024;
+  auto status = LibFlacReadCallback(/*stream_decoder=*/nullptr, buffer, &bytes,
+                                    &flac_decoder_);
+  EXPECT_EQ(status, FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM);
+  EXPECT_EQ(bytes, 0);
+}
+
+TEST_F(FlacDecoderStreamCallbacksTest, ReadCallbackFrameTooLarge) {
+  FLAC__byte buffer[1024];
+  size_t bytes = 1024;
+  flac_decoder_.SetEncodedFrame(std::vector<uint8_t>(1025));
+  auto status = LibFlacReadCallback(/*stream_decoder=*/nullptr, buffer, &bytes,
+                                    &flac_decoder_);
+  EXPECT_EQ(status, FLAC__STREAM_DECODER_READ_STATUS_ABORT);
+  EXPECT_EQ(bytes, 0);
+}
+
+TEST_F(FlacDecoderStreamCallbacksTest, ReadCallbackSuccess) {
+  FLAC__byte buffer[1024];
+  size_t bytes = 1028;
+  const std::vector<uint8_t> encoded_frame(1024, 1);
+  flac_decoder_.SetEncodedFrame(encoded_frame);
+  auto status = LibFlacReadCallback(/*stream_decoder=*/nullptr, buffer, &bytes,
+                                    &flac_decoder_);
+  EXPECT_EQ(status, FLAC__STREAM_DECODER_READ_STATUS_CONTINUE);
+  EXPECT_EQ(bytes, 1024);
+  EXPECT_THAT(buffer, ElementsAreArray(encoded_frame));
+}
+
+}  // namespace
+}  // namespace iamf_tools