AudioFrameDecoder: Process a single frame at a time.

  - Instead of outputting by appending to a list, directly process one frame at a time.
    - The new interface is more generic and convenient if any call sites have their input in a different form or a different output arrangement.
    - Removes the thin loop which had to perform lookups each iteration anyway.
  - Directly return `abls::StatusOr`. Instead of leaving the reference in unknown state.
  - Simplify some tests. Empty list input, or append are no longer possible.

PiperOrigin-RevId: 691387035

iamf/cli/BUILD

@@ -45,6 +45,7 @@ cc_library(
         "@com_google_absl//absl/container:node_hash_map",
         "@com_google_absl//absl/log",
         "@com_google_absl//absl/status",
+        "@com_google_absl//absl/status:statusor",
         "@com_google_absl//absl/strings",
     ],
 )

iamf/cli/audio_frame_decoder.cc

@@ -11,7 +11,7 @@
  */
 #include "iamf/cli/audio_frame_decoder.h"
 
-#include <list>
+#include <cstdint>
 #include <memory>
 #include <utility>
 #include <vector>
@@ -20,7 +20,6 @@
 #include "absl/log/log.h"
 #include "absl/status/status.h"
 #include "absl/strings/str_cat.h"
-#include "absl/strings/string_view.h"
 #include "iamf/cli/audio_element_with_data.h"
 #include "iamf/cli/audio_frame_with_data.h"
 #include "iamf/cli/codec/aac_decoder.h"
@@ -63,29 +62,6 @@ absl::Status InitializeDecoder(const CodecConfigObu& codec_config,
   return absl::OkStatus();
 }
 
-absl::Status DecodeAudioFrame(const AudioFrameWithData& encoded_frame,
-                              DecoderBase* decoder,
-                              DecodedAudioFrame& decoded_audio_frame) {
-  // Copy over some fields from the encoded frame.
-  decoded_audio_frame.substream_id = encoded_frame.obu.GetSubstreamId();
-  decoded_audio_frame.start_timestamp = encoded_frame.start_timestamp;
-  decoded_audio_frame.end_timestamp = encoded_frame.end_timestamp;
-  decoded_audio_frame.samples_to_trim_at_end =
-      encoded_frame.obu.header_.num_samples_to_trim_at_end;
-  decoded_audio_frame.samples_to_trim_at_start =
-      encoded_frame.obu.header_.num_samples_to_trim_at_start;
-  decoded_audio_frame.down_mixing_params = encoded_frame.down_mixing_params;
-  decoded_audio_frame.audio_element_with_data =
-      encoded_frame.audio_element_with_data;
-
-  // Decode the samples with the specific decoder associated with this
-  // substream.
-  RETURN_IF_NOT_OK(decoder->DecodeAudioFrame(
-      encoded_frame.obu.audio_frame_, decoded_audio_frame.decoded_samples));
-
-  return absl::OkStatus();
-}
-
 }  // namespace
 
 // Initializes all decoders and wav writers based on the corresponding Audio
@@ -111,26 +87,35 @@ absl::Status AudioFrameDecoder::InitDecodersForSubstreams(
   return absl::OkStatus();
 }
 
-absl::Status AudioFrameDecoder::Decode(
-    const std::list<AudioFrameWithData>& encoded_audio_frames,
-    std::list<DecodedAudioFrame>& decoded_audio_frames) {
-  // Decode all frames in all substreams.
-  for (const auto& audio_frame : encoded_audio_frames) {
-    auto decoder_iter =
-        substream_id_to_decoder_.find(audio_frame.obu.GetSubstreamId());
-    if (decoder_iter == substream_id_to_decoder_.end()) {
-      return absl::InvalidArgumentError(
-          absl::StrCat("No decoder found for substream ID: ",
-                       audio_frame.obu.GetSubstreamId()));
-    }
-
-    DecodedAudioFrame decoded_audio_frame;
-    RETURN_IF_NOT_OK(DecodeAudioFrame(audio_frame, decoder_iter->second.get(),
-                                      decoded_audio_frame));
-    decoded_audio_frames.push_back(std::move(decoded_audio_frame));
+absl::StatusOr<DecodedAudioFrame> AudioFrameDecoder::Decode(
+    const AudioFrameWithData& audio_frame) {
+  auto decoder_iter =
+      substream_id_to_decoder_.find(audio_frame.obu.GetSubstreamId());
+  if (decoder_iter == substream_id_to_decoder_.end() ||
+      decoder_iter->second == nullptr) {
+    return absl::InvalidArgumentError(
+        absl::StrCat("No decoder found for substream ID: ",
+                     audio_frame.obu.GetSubstreamId()));
   }
-
-  return absl::OkStatus();
+  // Decode the samples with the specific decoder associated with this
+  // substream.
+  std::vector<std::vector<int32_t>> decoded_samples;
+  RETURN_IF_NOT_OK(decoder_iter->second->DecodeAudioFrame(
+      audio_frame.obu.audio_frame_, decoded_samples));
+
+  // Return a frame. Most fields are copied from the encoded frame.
+  return DecodedAudioFrame{
+      .substream_id = audio_frame.obu.GetSubstreamId(),
+      .start_timestamp = audio_frame.start_timestamp,
+      .end_timestamp = audio_frame.end_timestamp,
+      .samples_to_trim_at_end =
+          audio_frame.obu.header_.num_samples_to_trim_at_end,
+      .samples_to_trim_at_start =
+          audio_frame.obu.header_.num_samples_to_trim_at_start,
+      .decoded_samples = decoded_samples,
+      .down_mixing_params = audio_frame.down_mixing_params,
+      .audio_element_with_data = audio_frame.audio_element_with_data,
+  };
 }
 
 }  // namespace iamf_tools

iamf/cli/audio_frame_decoder.h

@@ -13,12 +13,12 @@
 #define CLI_AUDIO_FRAME_DECODER_H_
 
 #include <cstdint>
-#include <list>
 #include <memory>
 #include <vector>
 
 #include "absl/container/node_hash_map.h"
 #include "absl/status/status.h"
+#include "absl/status/statusor.h"
 #include "iamf/cli/audio_element_with_data.h"
 #include "iamf/cli/audio_frame_with_data.h"
 #include "iamf/cli/codec/decoder_base.h"
@@ -85,14 +85,13 @@ class AudioFrameDecoder {
       const SubstreamIdLabelsMap& substream_id_to_labels,
       const CodecConfigObu& codec_config);
 
-  /*!\brief Decodes a list of Audio Frame OBUs.
+  /*!\brief Decodes an Audio Frame OBU.
    *
-   * \param encoded_audio_frames Input Audio Frame OBUs.
-   * \param decoded_audio_frames Output decoded audio frames.
-   * \return `absl::OkStatus()` on success. A specific status on failure.
+   * \param encoded_audio_frame Input Audio Frame OBU.
+   * \return Decoded audio frame on success. A specific status on failure.
    */
-  absl::Status Decode(const std::list<AudioFrameWithData>& encoded_audio_frames,
-                      std::list<DecodedAudioFrame>& decoded_audio_frames);
+  absl::StatusOr<DecodedAudioFrame> Decode(
+      const AudioFrameWithData& encoded_audio_frame);
 
  private:
   // A map of substream IDs to the relevant decoder and codec config. This is

iamf/cli/iamf_encoder.cc

@@ -16,6 +16,7 @@
 #include <list>
 #include <memory>
 #include <optional>
+#include <utility>
 #include <vector>
 
 #include "absl/container/flat_hash_map.h"
@@ -233,8 +234,13 @@ absl::Status IamfEncoder::OutputTemporalUnit(
   // Decode the audio frames. They are required to determine the demixed
   // frames.
   std::list<DecodedAudioFrame> decoded_audio_frames;
-  RETURN_IF_NOT_OK(
-      audio_frame_decoder_->Decode(audio_frames, decoded_audio_frames));
+  for (const auto& audio_frame : audio_frames) {
+    auto decoded_audio_frame = audio_frame_decoder_->Decode(audio_frame);
+    if (!decoded_audio_frame.ok()) {
+      return decoded_audio_frame.status();
+    }
+    decoded_audio_frames.emplace_back(*decoded_audio_frame);
+  }
 
   // Demix the audio frames.
   IdLabeledFrameMap id_to_labeled_decoded_frame;