Add write callback function in flac decoder stream callbacks.

Also adds the requisite getters and setters in FlacDecoder.

PiperOrigin-RevId: 686681700

iamf/cli/codec/flac_decoder.h

@@ -66,8 +66,25 @@ class FlacDecoder : public DecoderBase {
    */
   std::vector<uint8_t> GetEncodedFrame() const { return encoded_frame_; }
 
+  /*!\brief Sets a decoded FLAC frame in decoder.decoded_frame_.
+   *
+   * \param decoded_frame Decoded FLAC frame.
+   */
+  void SetDecodedFrame(const std::vector<std::vector<int32_t>>& decoded_frame) {
+    decoded_frame_ = decoded_frame;
+  }
+
+  /*!\brief Retrieves the decoded FLAC frame in decoder.decoded_frame_.
+   *
+   * \return Vector of decoded FLAC samples.
+   */
+  std::vector<std::vector<int32_t>> GetDecodedFrame() const {
+    return decoded_frame_;
+  }
+
  private:
   std::vector<uint8_t> encoded_frame_ = {};
+  std::vector<std::vector<int32_t>> decoded_frame_ = {};
   const FlacDecoderConfig decoder_config_;
 };
 

iamf/cli/codec/flac_decoder_stream_callbacks.cc

@@ -13,9 +13,12 @@
 #include "iamf/cli/codec/flac_decoder_stream_callbacks.h"
 
 #include <cstddef>
+#include <cstdint>
+#include <vector>
 
 #include "absl/log/log.h"
 #include "iamf/cli/codec/flac_decoder.h"
+#include "include/FLAC/format.h"
 #include "include/FLAC/ordinals.h"
 #include "include/FLAC/stream_decoder.h"
 
@@ -44,4 +47,23 @@ FLAC__StreamDecoderReadStatus LibFlacReadCallback(
   return FLAC__STREAM_DECODER_READ_STATUS_CONTINUE;
 }
 
+FLAC__StreamDecoderWriteStatus LibFlacWriteCallback(
+    const FLAC__StreamDecoder* /*decoder*/, const FLAC__Frame* frame,
+    const FLAC__int32* const buffer[], void* client_data) {
+  std::vector<std::vector<int32_t>> decoded_samples(frame->header.channels);
+  auto* flac_decoder = static_cast<FlacDecoder*>(client_data);
+  const auto num_samples_per_channel = frame->header.blocksize;
+  // Note: libFLAC represents data in a planar fashion, so each channel is
+  // stored in a separate array.
+  for (int i = 0; i < frame->header.channels; ++i) {
+    decoded_samples[i].resize(num_samples_per_channel);
+    const FLAC__int32* const channel_buffer = buffer[i];
+    for (int j = 0; j < num_samples_per_channel; ++j) {
+      decoded_samples[i][j] = static_cast<int32_t>(channel_buffer[j]);
+    }
+  }
+  flac_decoder->SetDecodedFrame(decoded_samples);
+  return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;
+}
+
 }  // namespace iamf_tools

iamf/cli/codec/flac_decoder_stream_callbacks.h

@@ -15,6 +15,7 @@
 
 #include <cstddef>
 
+#include "include/FLAC/format.h"
 #include "include/FLAC/ordinals.h"
 #include "include/FLAC/stream_decoder.h"
 
@@ -38,6 +39,28 @@ FLAC__StreamDecoderReadStatus LibFlacReadCallback(
     const FLAC__StreamDecoder* decoder, FLAC__byte buffer[], size_t* bytes,
     void* client_data);
 
+/*!\brief Writes a decoded flac frame to an instance of FlacDecoder.
+ *
+ * This callback function is used to write out a decoded frame from the libflac
+ * decoder.
+ *
+ * \param decoder Unused libflac stream decoder. This parameter is not used in
+ *        this implementation, but is included to override the libflac
+ *        signature.
+ * \param frame libflac encoded frame metadata.
+ * \param buffer Array of pointers to decoded channels of data. Each pointer
+ *        will point to an array of signed samples of length
+ *        `frame->header.blocksize`. Channels will be ordered according to the
+ *        FLAC specification.
+ * \param client_data Universal pointer, which in this case should point to
+ *        FlacDecoder.
+ *
+ * \return A libflac write status indicating whether the write was successful.
+ */
+FLAC__StreamDecoderWriteStatus LibFlacWriteCallback(
+    const FLAC__StreamDecoder* /*decoder*/, const FLAC__Frame* frame,
+    const FLAC__int32* const buffer[], void* client_data);
+
 }  // namespace iamf_tools
 
 #endif  // CLI_CODEC_FLAC_DECODER_STREAM_CALLBACKS_H_

iamf/cli/codec/tests/flac_decoder_stream_callbacks_test.cc

@@ -22,6 +22,7 @@
 #include "iamf/obu/codec_config.h"
 #include "iamf/obu/decoder_config/flac_decoder_config.h"
 #include "iamf/obu/obu_header.h"
+#include "include/FLAC/format.h"
 #include "include/FLAC/ordinals.h"
 #include "include/FLAC/stream_decoder.h"
 
@@ -76,5 +77,37 @@ TEST_F(FlacDecoderStreamCallbacksTest, ReadCallbackSuccess) {
   EXPECT_THAT(buffer, ElementsAreArray(encoded_frame));
 }
 
+TEST_F(FlacDecoderStreamCallbacksTest, WriteCallbackSuccess32BitSamples) {
+  FLAC__Frame frame;
+  frame.header.channels = 2;
+  frame.header.blocksize = 3;
+  frame.header.bits_per_sample = 32;
+  FLAC__int32 channel_0[] = {1, 0x7fffffff, 3};
+  FLAC__int32 channel_1[] = {2, 3, 4};
+  const FLAC__int32 *const buffer[] = {channel_0, channel_1};
+  auto status = LibFlacWriteCallback(/*stream_decoder=*/nullptr, &frame, buffer,
+                                     &flac_decoder_);
+  EXPECT_EQ(status, FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE);
+  EXPECT_THAT(flac_decoder_.GetDecodedFrame(),
+              ElementsAreArray(std::vector<std::vector<int32_t>>(
+                  {{1, 0x7fffffff, 3}, {2, 3, 4}})));
+}
+
+TEST_F(FlacDecoderStreamCallbacksTest, WriteCallbackSuccess16BitSamples) {
+  FLAC__Frame frame;
+  frame.header.channels = 2;
+  frame.header.blocksize = 2;
+  frame.header.bits_per_sample = 16;
+  FLAC__int32 channel_0[] = {0x11110000, 0x7fff0000};
+  FLAC__int32 channel_1[] = {0x01010000, 0x22220000};
+  const FLAC__int32 *const buffer[] = {channel_0, channel_1};
+  auto status = LibFlacWriteCallback(/*stream_decoder=*/nullptr, &frame, buffer,
+                                     &flac_decoder_);
+  EXPECT_EQ(status, FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE);
+  EXPECT_THAT(flac_decoder_.GetDecodedFrame(),
+              ElementsAreArray(std::vector<std::vector<int32_t>>(
+                  {{0x11110000, 0x7fff0000}, {0x01010000, 0x22220000}})));
+}
+
 }  // namespace
 }  // namespace iamf_tools