Moved codec-specific audio packet splitting into decoders.

There's still some code run specifically for Opus w/ FEC. It will be
addressed in a separate CL.

BUG=webrtc:5805

Review-Url: https://codereview.webrtc.org/2326003002
Cr-Commit-Position: refs/heads/master@{#14319}
diff --git a/webrtc/modules/audio_coding/codecs/audio_decoder.cc b/webrtc/modules/audio_coding/codecs/audio_decoder.cc
index 9dbecd5..6c67924 100644
--- a/webrtc/modules/audio_coding/codecs/audio_decoder.cc
+++ b/webrtc/modules/audio_coding/codecs/audio_decoder.cc
@@ -11,6 +11,8 @@
 #include "webrtc/modules/audio_coding/codecs/audio_decoder.h"
 
 #include <assert.h>
+#include <memory>
+#include <utility>
 
 #include <utility>
 
@@ -18,56 +20,10 @@
 #include "webrtc/base/checks.h"
 #include "webrtc/base/sanitizer.h"
 #include "webrtc/base/trace_event.h"
+#include "webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.h"
 
 namespace webrtc {
 
-namespace {
-class LegacyFrame final : public AudioDecoder::EncodedAudioFrame {
- public:
-  LegacyFrame(AudioDecoder* decoder,
-              rtc::Buffer&& payload,
-              bool is_primary_payload)
-      : decoder_(decoder),
-        payload_(std::move(payload)),
-        is_primary_payload_(is_primary_payload) {}
-
-  size_t Duration() const override {
-    int ret;
-    if (is_primary_payload_) {
-      ret = decoder_->PacketDuration(payload_.data(), payload_.size());
-    } else {
-      ret = decoder_->PacketDurationRedundant(payload_.data(), payload_.size());
-    }
-    return (ret < 0) ? 0 : static_cast<size_t>(ret);
-  }
-
-  rtc::Optional<DecodeResult> Decode(
-      rtc::ArrayView<int16_t> decoded) const override {
-    AudioDecoder::SpeechType speech_type = AudioDecoder::kSpeech;
-    int ret;
-    if (is_primary_payload_) {
-      ret = decoder_->Decode(
-          payload_.data(), payload_.size(), decoder_->SampleRateHz(),
-          decoded.size() * sizeof(int16_t), decoded.data(), &speech_type);
-    } else {
-      ret = decoder_->DecodeRedundant(
-          payload_.data(), payload_.size(), decoder_->SampleRateHz(),
-          decoded.size() * sizeof(int16_t), decoded.data(), &speech_type);
-    }
-
-    if (ret < 0)
-      return rtc::Optional<DecodeResult>();
-
-    return rtc::Optional<DecodeResult>({static_cast<size_t>(ret), speech_type});
-  }
-
- private:
-  AudioDecoder* const decoder_;
-  const rtc::Buffer payload_;
-  const bool is_primary_payload_;
-};
-}  // namespace
-
 AudioDecoder::ParseResult::ParseResult() = default;
 AudioDecoder::ParseResult::ParseResult(ParseResult&& b) = default;
 AudioDecoder::ParseResult::ParseResult(uint32_t timestamp,
@@ -86,7 +42,7 @@
     bool is_primary) {
   std::vector<ParseResult> results;
   std::unique_ptr<EncodedAudioFrame> frame(
-      new LegacyFrame(this, std::move(payload), is_primary));
+      new LegacyEncodedAudioFrame(this, std::move(payload), is_primary));
   results.emplace_back(timestamp, is_primary, std::move(frame));
   return results;
 }
diff --git a/webrtc/modules/audio_coding/codecs/audio_decoder.h b/webrtc/modules/audio_coding/codecs/audio_decoder.h
index 9608c32..b6338d2 100644
--- a/webrtc/modules/audio_coding/codecs/audio_decoder.h
+++ b/webrtc/modules/audio_coding/codecs/audio_decoder.h
@@ -11,7 +11,8 @@
 #ifndef WEBRTC_MODULES_AUDIO_CODING_NETEQ_INCLUDE_AUDIO_DECODER_H_
 #define WEBRTC_MODULES_AUDIO_CODING_NETEQ_INCLUDE_AUDIO_DECODER_H_
 
-#include <stdlib.h>  // NULL
+#include <memory>
+#include <vector>
 
 #include <memory>
 #include <vector>
diff --git a/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.cc b/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.cc
index af164c4..f2fdb1f 100644
--- a/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.cc
+++ b/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.cc
@@ -10,12 +10,21 @@
 
 #include "webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.h"
 
+#include "webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.h"
 #include "webrtc/modules/audio_coding/codecs/g711/g711_interface.h"
 
 namespace webrtc {
 
 void AudioDecoderPcmU::Reset() {}
 
+std::vector<AudioDecoder::ParseResult> AudioDecoderPcmU::ParsePayload(
+    rtc::Buffer&& payload,
+    uint32_t timestamp,
+    bool is_primary) {
+  return LegacyEncodedAudioFrame::SplitBySamples(
+      this, std::move(payload), timestamp, is_primary, 8 * num_channels_, 8);
+}
+
 int AudioDecoderPcmU::SampleRateHz() const {
   return 8000;
 }
@@ -44,6 +53,14 @@
 
 void AudioDecoderPcmA::Reset() {}
 
+std::vector<AudioDecoder::ParseResult> AudioDecoderPcmA::ParsePayload(
+    rtc::Buffer&& payload,
+    uint32_t timestamp,
+    bool is_primary) {
+  return LegacyEncodedAudioFrame::SplitBySamples(
+      this, std::move(payload), timestamp, is_primary, 8 * num_channels_, 8);
+}
+
 int AudioDecoderPcmA::SampleRateHz() const {
   return 8000;
 }
diff --git a/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.h b/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.h
index 7fdc359..ed39021 100644
--- a/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.h
+++ b/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.h
@@ -23,6 +23,9 @@
     RTC_DCHECK_GE(num_channels, 1u);
   }
   void Reset() override;
+  std::vector<ParseResult> ParsePayload(rtc::Buffer&& payload,
+                                        uint32_t timestamp,
+                                        bool is_primary) override;
   int PacketDuration(const uint8_t* encoded, size_t encoded_len) const override;
   int SampleRateHz() const override;
   size_t Channels() const override;
@@ -45,6 +48,9 @@
     RTC_DCHECK_GE(num_channels, 1u);
   }
   void Reset() override;
+  std::vector<ParseResult> ParsePayload(rtc::Buffer&& payload,
+                                        uint32_t timestamp,
+                                        bool is_primary) override;
   int PacketDuration(const uint8_t* encoded, size_t encoded_len) const override;
   int SampleRateHz() const override;
   size_t Channels() const override;
diff --git a/webrtc/modules/audio_coding/codecs/g711/g711.gypi b/webrtc/modules/audio_coding/codecs/g711/g711.gypi
index d209628..207790f 100644
--- a/webrtc/modules/audio_coding/codecs/g711/g711.gypi
+++ b/webrtc/modules/audio_coding/codecs/g711/g711.gypi
@@ -13,6 +13,8 @@
       'type': 'static_library',
       'dependencies': [
         'audio_encoder_interface',
+        'audio_decoder_interface',
+        'legacy_encoded_audio_frame',
       ],
       'sources': [
         'audio_decoder_pcm.cc',
diff --git a/webrtc/modules/audio_coding/codecs/g722/audio_decoder_g722.cc b/webrtc/modules/audio_coding/codecs/g722/audio_decoder_g722.cc
index 379293b..93b24bd 100644
--- a/webrtc/modules/audio_coding/codecs/g722/audio_decoder_g722.cc
+++ b/webrtc/modules/audio_coding/codecs/g722/audio_decoder_g722.cc
@@ -13,6 +13,7 @@
 #include <string.h>
 
 #include "webrtc/base/checks.h"
+#include "webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.h"
 #include "webrtc/modules/audio_coding/codecs/g722/g722_interface.h"
 
 namespace webrtc {
@@ -47,6 +48,14 @@
   WebRtcG722_DecoderInit(dec_state_);
 }
 
+std::vector<AudioDecoder::ParseResult> AudioDecoderG722::ParsePayload(
+    rtc::Buffer&& payload,
+    uint32_t timestamp,
+    bool is_primary) {
+  return LegacyEncodedAudioFrame::SplitBySamples(this, std::move(payload),
+                                                 timestamp, is_primary, 8, 16);
+}
+
 int AudioDecoderG722::PacketDuration(const uint8_t* encoded,
                                      size_t encoded_len) const {
   // 1/2 encoded byte per sample per channel.
@@ -117,6 +126,14 @@
   WebRtcG722_DecoderInit(dec_state_right_);
 }
 
+std::vector<AudioDecoder::ParseResult> AudioDecoderG722Stereo::ParsePayload(
+    rtc::Buffer&& payload,
+    uint32_t timestamp,
+    bool is_primary) {
+  return LegacyEncodedAudioFrame::SplitBySamples(
+      this, std::move(payload), timestamp, is_primary, 2 * 8, 16);
+}
+
 // Split the stereo packet and place left and right channel after each other
 // in the output array.
 void AudioDecoderG722Stereo::SplitStereoPacket(const uint8_t* encoded,
diff --git a/webrtc/modules/audio_coding/codecs/g722/audio_decoder_g722.h b/webrtc/modules/audio_coding/codecs/g722/audio_decoder_g722.h
index ccca73d..ad39619 100644
--- a/webrtc/modules/audio_coding/codecs/g722/audio_decoder_g722.h
+++ b/webrtc/modules/audio_coding/codecs/g722/audio_decoder_g722.h
@@ -24,6 +24,9 @@
   ~AudioDecoderG722() override;
   bool HasDecodePlc() const override;
   void Reset() override;
+  std::vector<ParseResult> ParsePayload(rtc::Buffer&& payload,
+                                        uint32_t timestamp,
+                                        bool is_primary) override;
   int PacketDuration(const uint8_t* encoded, size_t encoded_len) const override;
   int SampleRateHz() const override;
   size_t Channels() const override;
@@ -45,6 +48,9 @@
   AudioDecoderG722Stereo();
   ~AudioDecoderG722Stereo() override;
   void Reset() override;
+  std::vector<ParseResult> ParsePayload(rtc::Buffer&& payload,
+                                        uint32_t timestamp,
+                                        bool is_primary) override;
   int SampleRateHz() const override;
   size_t Channels() const override;
 
diff --git a/webrtc/modules/audio_coding/codecs/g722/g722.gypi b/webrtc/modules/audio_coding/codecs/g722/g722.gypi
index 13c6f2d..a661a75 100644
--- a/webrtc/modules/audio_coding/codecs/g722/g722.gypi
+++ b/webrtc/modules/audio_coding/codecs/g722/g722.gypi
@@ -12,6 +12,8 @@
       'type': 'static_library',
       'dependencies': [
         'audio_encoder_interface',
+        'audio_decoder_interface',
+        'legacy_encoded_audio_frame',
       ],
       'sources': [
         'audio_decoder_g722.cc',
diff --git a/webrtc/modules/audio_coding/codecs/ilbc/audio_decoder_ilbc.cc b/webrtc/modules/audio_coding/codecs/ilbc/audio_decoder_ilbc.cc
index dab5805..b4bd599 100644
--- a/webrtc/modules/audio_coding/codecs/ilbc/audio_decoder_ilbc.cc
+++ b/webrtc/modules/audio_coding/codecs/ilbc/audio_decoder_ilbc.cc
@@ -11,7 +11,9 @@
 #include "webrtc/modules/audio_coding/codecs/ilbc/audio_decoder_ilbc.h"
 
 #include "webrtc/base/checks.h"
+#include "webrtc/base/logging.h"
 #include "webrtc/modules/audio_coding/codecs/ilbc/ilbc.h"
+#include "webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.h"
 
 namespace webrtc {
 
@@ -49,6 +51,53 @@
   WebRtcIlbcfix_Decoderinit30Ms(dec_state_);
 }
 
+std::vector<AudioDecoder::ParseResult> AudioDecoderIlbc::ParsePayload(
+    rtc::Buffer&& payload,
+    uint32_t timestamp,
+    bool is_primary) {
+  std::vector<ParseResult> results;
+  size_t bytes_per_frame;
+  int timestamps_per_frame;
+  if (payload.size() >= 950) {
+    LOG(LS_WARNING) << "AudioDecoderIlbc::ParsePayload: Payload too large";
+    return results;
+  }
+  if (payload.size() % 38 == 0) {
+    // 20 ms frames.
+    bytes_per_frame = 38;
+    timestamps_per_frame = 160;
+  } else if (payload.size() % 50 == 0) {
+    // 30 ms frames.
+    bytes_per_frame = 50;
+    timestamps_per_frame = 240;
+  } else {
+    LOG(LS_WARNING) << "AudioDecoderIlbc::ParsePayload: Invalid payload";
+    return results;
+  }
+
+  RTC_DCHECK_EQ(0u, payload.size() % bytes_per_frame);
+  if (payload.size() == bytes_per_frame) {
+    std::unique_ptr<EncodedAudioFrame> frame(
+        new LegacyEncodedAudioFrame(this, std::move(payload), is_primary));
+    results.emplace_back(timestamp, is_primary, std::move(frame));
+  } else {
+    size_t byte_offset;
+    uint32_t timestamp_offset;
+    for (byte_offset = 0, timestamp_offset = 0;
+         byte_offset < payload.size();
+         byte_offset += bytes_per_frame,
+             timestamp_offset += timestamps_per_frame) {
+      rtc::Buffer new_payload(payload.data() + byte_offset, bytes_per_frame);
+      std::unique_ptr<EncodedAudioFrame> frame(new LegacyEncodedAudioFrame(
+          this, std::move(new_payload), is_primary));
+      results.emplace_back(timestamp + timestamp_offset, is_primary,
+                           std::move(frame));
+    }
+  }
+
+  return results;
+}
+
 int AudioDecoderIlbc::SampleRateHz() const {
   return 8000;
 }
diff --git a/webrtc/modules/audio_coding/codecs/ilbc/audio_decoder_ilbc.h b/webrtc/modules/audio_coding/codecs/ilbc/audio_decoder_ilbc.h
index 1083479..fdc856e 100644
--- a/webrtc/modules/audio_coding/codecs/ilbc/audio_decoder_ilbc.h
+++ b/webrtc/modules/audio_coding/codecs/ilbc/audio_decoder_ilbc.h
@@ -25,6 +25,9 @@
   bool HasDecodePlc() const override;
   size_t DecodePlc(size_t num_frames, int16_t* decoded) override;
   void Reset() override;
+  std::vector<ParseResult> ParsePayload(rtc::Buffer&& payload,
+                                        uint32_t timestamp,
+                                        bool is_primary) override;
   int SampleRateHz() const override;
   size_t Channels() const override;
 
diff --git a/webrtc/modules/audio_coding/codecs/ilbc/ilbc_unittest.cc b/webrtc/modules/audio_coding/codecs/ilbc/ilbc_unittest.cc
index c23cbc4..a8b76a5 100644
--- a/webrtc/modules/audio_coding/codecs/ilbc/ilbc_unittest.cc
+++ b/webrtc/modules/audio_coding/codecs/ilbc/ilbc_unittest.cc
@@ -11,6 +11,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "webrtc/modules/audio_coding/codecs/ilbc/audio_decoder_ilbc.h"
 #include "webrtc/modules/audio_coding/codecs/ilbc/audio_encoder_ilbc.h"
+#include "webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.h"
 
 namespace webrtc {
 
@@ -54,4 +55,85 @@
                            decoded_samples.data(), &speech_type));
 }
 
+class SplitIlbcTest : public ::testing::TestWithParam<std::pair<int, int> > {
+ protected:
+  virtual void SetUp() {
+    const std::pair<int, int> parameters = GetParam();
+    num_frames_ = parameters.first;
+    frame_length_ms_ = parameters.second;
+    frame_length_bytes_ = (frame_length_ms_ == 20) ? 38 : 50;
+  }
+  size_t num_frames_;
+  int frame_length_ms_;
+  size_t frame_length_bytes_;
+};
+
+TEST_P(SplitIlbcTest, NumFrames) {
+  AudioDecoderIlbc decoder;
+  const size_t frame_length_samples = frame_length_ms_ * 8;
+  const auto generate_payload = [] (size_t payload_length_bytes) {
+    rtc::Buffer payload(payload_length_bytes);
+    // Fill payload with increasing integers {0, 1, 2, ...}.
+    for (size_t i = 0; i < payload.size(); ++i) {
+      payload[i] = static_cast<uint8_t>(i);
+    }
+    return payload;
+  };
+
+  const auto results = decoder.ParsePayload(
+      generate_payload(frame_length_bytes_ * num_frames_), 0, true);
+  EXPECT_EQ(num_frames_, results.size());
+
+  size_t frame_num = 0;
+  uint8_t payload_value = 0;
+  for (const auto& result : results) {
+    EXPECT_EQ(frame_length_samples * frame_num, result.timestamp);
+    const LegacyEncodedAudioFrame* frame =
+        static_cast<const LegacyEncodedAudioFrame*>(result.frame.get());
+    const rtc::Buffer& payload = frame->payload();
+    EXPECT_EQ(frame_length_bytes_, payload.size());
+    for (size_t i = 0; i < payload.size(); ++i, ++payload_value) {
+      EXPECT_EQ(payload_value, payload[i]);
+    }
+    ++frame_num;
+  }
+}
+
+// Test 1 through 5 frames of 20 and 30 ms size.
+// Also test the maximum number of frames in one packet for 20 and 30 ms.
+// The maximum is defined by the largest payload length that can be uniquely
+// resolved to a frame size of either 38 bytes (20 ms) or 50 bytes (30 ms).
+INSTANTIATE_TEST_CASE_P(
+    IlbcTest, SplitIlbcTest,
+    ::testing::Values(std::pair<int, int>(1, 20),  // 1 frame, 20 ms.
+                      std::pair<int, int>(2, 20),  // 2 frames, 20 ms.
+                      std::pair<int, int>(3, 20),  // And so on.
+                      std::pair<int, int>(4, 20),
+                      std::pair<int, int>(5, 20),
+                      std::pair<int, int>(24, 20),
+                      std::pair<int, int>(1, 30),
+                      std::pair<int, int>(2, 30),
+                      std::pair<int, int>(3, 30),
+                      std::pair<int, int>(4, 30),
+                      std::pair<int, int>(5, 30),
+                      std::pair<int, int>(18, 30)));
+
+// Test too large payload size.
+TEST(IlbcTest, SplitTooLargePayload) {
+  AudioDecoderIlbc decoder;
+  constexpr size_t kPayloadLengthBytes = 950;
+  const auto results =
+      decoder.ParsePayload(rtc::Buffer(kPayloadLengthBytes), 0, true);
+  EXPECT_TRUE(results.empty());
+}
+
+// Payload not an integer number of frames.
+TEST(IlbcTest, SplitUnevenPayload) {
+  AudioDecoderIlbc decoder;
+  constexpr size_t kPayloadLengthBytes = 39;  // Not an even number of frames.
+  const auto results =
+      decoder.ParsePayload(rtc::Buffer(kPayloadLengthBytes), 0, true);
+  EXPECT_TRUE(results.empty());
+}
+
 }  // namespace webrtc
diff --git a/webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.cc b/webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.cc
new file mode 100644
index 0000000..5e6ff01
--- /dev/null
+++ b/webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.cc
@@ -0,0 +1,105 @@
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.h"
+
+#include <algorithm>
+#include <memory>
+#include <utility>
+
+namespace webrtc {
+
+LegacyEncodedAudioFrame::LegacyEncodedAudioFrame(AudioDecoder* decoder,
+                                                 rtc::Buffer&& payload,
+                                                 bool is_primary_payload)
+    : decoder_(decoder),
+      payload_(std::move(payload)),
+      is_primary_payload_(is_primary_payload) {}
+
+LegacyEncodedAudioFrame::~LegacyEncodedAudioFrame() = default;
+
+size_t LegacyEncodedAudioFrame::Duration() const {
+  int ret;
+  if (is_primary_payload_) {
+    ret = decoder_->PacketDuration(payload_.data(), payload_.size());
+  } else {
+    ret = decoder_->PacketDurationRedundant(payload_.data(), payload_.size());
+  }
+  return (ret < 0) ? 0 : static_cast<size_t>(ret);
+}
+
+rtc::Optional<AudioDecoder::EncodedAudioFrame::DecodeResult>
+LegacyEncodedAudioFrame::Decode(rtc::ArrayView<int16_t> decoded) const {
+  AudioDecoder::SpeechType speech_type = AudioDecoder::kSpeech;
+  int ret;
+  if (is_primary_payload_) {
+    ret = decoder_->Decode(
+        payload_.data(), payload_.size(), decoder_->SampleRateHz(),
+        decoded.size() * sizeof(int16_t), decoded.data(), &speech_type);
+  } else {
+    ret = decoder_->DecodeRedundant(
+        payload_.data(), payload_.size(), decoder_->SampleRateHz(),
+        decoded.size() * sizeof(int16_t), decoded.data(), &speech_type);
+  }
+
+  if (ret < 0)
+    return rtc::Optional<DecodeResult>();
+
+  return rtc::Optional<DecodeResult>({static_cast<size_t>(ret), speech_type});
+}
+
+std::vector<AudioDecoder::ParseResult> LegacyEncodedAudioFrame::SplitBySamples(
+    AudioDecoder* decoder,
+    rtc::Buffer&& payload,
+    uint32_t timestamp,
+    bool is_primary,
+    size_t bytes_per_ms,
+    uint32_t timestamps_per_ms) {
+  RTC_DCHECK(payload.data());
+  std::vector<AudioDecoder::ParseResult> results;
+  size_t split_size_bytes = payload.size();
+
+  // Find a "chunk size" >= 20 ms and < 40 ms.
+  const size_t min_chunk_size = bytes_per_ms * 20;
+  if (min_chunk_size >= payload.size()) {
+    std::unique_ptr<LegacyEncodedAudioFrame> frame(
+        new LegacyEncodedAudioFrame(decoder, std::move(payload), is_primary));
+    results.emplace_back(timestamp, is_primary, std::move(frame));
+  } else {
+    // Reduce the split size by half as long as |split_size_bytes| is at least
+    // twice the minimum chunk size (so that the resulting size is at least as
+    // large as the minimum chunk size).
+    while (split_size_bytes >= 2 * min_chunk_size) {
+      split_size_bytes /= 2;
+    }
+
+    const uint32_t timestamps_per_chunk = static_cast<uint32_t>(
+        split_size_bytes * timestamps_per_ms / bytes_per_ms);
+    size_t byte_offset;
+    uint32_t timestamp_offset;
+    for (byte_offset = 0, timestamp_offset = 0;
+         byte_offset < payload.size();
+         byte_offset += split_size_bytes,
+             timestamp_offset += timestamps_per_chunk) {
+      split_size_bytes =
+          std::min(split_size_bytes, payload.size() - byte_offset);
+      rtc::Buffer new_payload(payload.data() + byte_offset, split_size_bytes);
+      std::unique_ptr<LegacyEncodedAudioFrame> frame(
+          new LegacyEncodedAudioFrame(decoder, std::move(new_payload),
+                                      is_primary));
+      results.emplace_back(timestamp + timestamp_offset, is_primary,
+                           std::move(frame));
+    }
+  }
+
+  return results;
+}
+
+}  // namespace webrtc
diff --git a/webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.h b/webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.h
new file mode 100644
index 0000000..1c9c3f5
--- /dev/null
+++ b/webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.h
@@ -0,0 +1,52 @@
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_CODING_CODECS_LEGACY_ENCODED_AUDIO_FRAME_H_
+#define WEBRTC_MODULES_AUDIO_CODING_CODECS_LEGACY_ENCODED_AUDIO_FRAME_H_
+
+#include <vector>
+
+#include "webrtc/base/array_view.h"
+#include "webrtc/modules/audio_coding/codecs/audio_decoder.h"
+
+namespace webrtc {
+
+class LegacyEncodedAudioFrame final : public AudioDecoder::EncodedAudioFrame {
+ public:
+  LegacyEncodedAudioFrame(AudioDecoder* decoder,
+                          rtc::Buffer&& payload,
+                          bool is_primary_payload);
+  ~LegacyEncodedAudioFrame() override;
+
+  static std::vector<AudioDecoder::ParseResult> SplitBySamples(
+      AudioDecoder* decoder,
+      rtc::Buffer&& payload,
+      uint32_t timestamp,
+      bool is_primary,
+      size_t bytes_per_ms,
+      uint32_t timestamps_per_ms);
+
+  size_t Duration() const override;
+
+  rtc::Optional<DecodeResult> Decode(
+      rtc::ArrayView<int16_t> decoded) const override;
+
+  // For testing:
+  const rtc::Buffer& payload() const { return payload_; }
+
+ private:
+  AudioDecoder* const decoder_;
+  const rtc::Buffer payload_;
+  const bool is_primary_payload_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_CODING_CODECS_LEGACY_ENCODED_AUDIO_FRAME_H_
diff --git a/webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame_unittest.cc b/webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame_unittest.cc
new file mode 100644
index 0000000..2a4d9ed
--- /dev/null
+++ b/webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame_unittest.cc
@@ -0,0 +1,169 @@
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/modules/audio_coding/acm2/rent_a_codec.h"
+#include "webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.h"
+
+namespace webrtc {
+
+using NetEqDecoder = acm2::RentACodec::NetEqDecoder;
+
+class SplitBySamplesTest : public ::testing::TestWithParam<NetEqDecoder> {
+ protected:
+  virtual void SetUp() {
+    decoder_type_ = GetParam();
+    switch (decoder_type_) {
+      case NetEqDecoder::kDecoderPCMu:
+      case NetEqDecoder::kDecoderPCMa:
+        bytes_per_ms_ = 8;
+        samples_per_ms_ = 8;
+        break;
+      case NetEqDecoder::kDecoderPCMu_2ch:
+      case NetEqDecoder::kDecoderPCMa_2ch:
+        bytes_per_ms_ = 2 * 8;
+        samples_per_ms_ = 8;
+        break;
+      case NetEqDecoder::kDecoderG722:
+        bytes_per_ms_ = 8;
+        samples_per_ms_ = 16;
+        break;
+      case NetEqDecoder::kDecoderPCM16B:
+        bytes_per_ms_ = 16;
+        samples_per_ms_ = 8;
+        break;
+      case NetEqDecoder::kDecoderPCM16Bwb:
+        bytes_per_ms_ = 32;
+        samples_per_ms_ = 16;
+        break;
+      case NetEqDecoder::kDecoderPCM16Bswb32kHz:
+        bytes_per_ms_ = 64;
+        samples_per_ms_ = 32;
+        break;
+      case NetEqDecoder::kDecoderPCM16Bswb48kHz:
+        bytes_per_ms_ = 96;
+        samples_per_ms_ = 48;
+        break;
+      case NetEqDecoder::kDecoderPCM16B_2ch:
+        bytes_per_ms_ = 2 * 16;
+        samples_per_ms_ = 8;
+        break;
+      case NetEqDecoder::kDecoderPCM16Bwb_2ch:
+        bytes_per_ms_ = 2 * 32;
+        samples_per_ms_ = 16;
+        break;
+      case NetEqDecoder::kDecoderPCM16Bswb32kHz_2ch:
+        bytes_per_ms_ = 2 * 64;
+        samples_per_ms_ = 32;
+        break;
+      case NetEqDecoder::kDecoderPCM16Bswb48kHz_2ch:
+        bytes_per_ms_ = 2 * 96;
+        samples_per_ms_ = 48;
+        break;
+      case NetEqDecoder::kDecoderPCM16B_5ch:
+        bytes_per_ms_ = 5 * 16;
+        samples_per_ms_ = 8;
+        break;
+      default:
+        assert(false);
+        break;
+    }
+  }
+  size_t bytes_per_ms_;
+  int samples_per_ms_;
+  NetEqDecoder decoder_type_;
+};
+
+// Test splitting sample-based payloads.
+TEST_P(SplitBySamplesTest, PayloadSizes) {
+  constexpr uint32_t kBaseTimestamp = 0x12345678;
+  struct ExpectedSplit {
+    size_t payload_size_ms;
+    size_t num_frames;
+    // For simplicity. We only expect up to two packets per split.
+    size_t frame_sizes[2];
+  };
+  // The payloads are expected to be split as follows:
+  // 10 ms -> 10 ms
+  // 20 ms -> 20 ms
+  // 30 ms -> 30 ms
+  // 40 ms -> 20 + 20 ms
+  // 50 ms -> 25 + 25 ms
+  // 60 ms -> 30 + 30 ms
+  ExpectedSplit expected_splits[] = {
+    {10, 1, {10}},
+    {20, 1, {20}},
+    {30, 1, {30}},
+    {40, 2, {20, 20}},
+    {50, 2, {25, 25}},
+    {60, 2, {30, 30}}
+  };
+
+  for (const auto& expected_split : expected_splits) {
+    // The payload values are set to steadily increase (modulo 256), so that the
+    // resulting frames can be checked and we can be reasonably certain no
+    // sample was missed or repeated.
+    const auto generate_payload = [] (size_t num_bytes) {
+      rtc::Buffer payload(num_bytes);
+      uint8_t value = 0;
+      // Allow wrap-around of value in counter below.
+      for (size_t i = 0; i != payload.size(); ++i, ++value) {
+        payload[i] = value;
+      }
+      return payload;
+    };
+
+    const auto results = LegacyEncodedAudioFrame::SplitBySamples(
+        nullptr,
+        generate_payload(expected_split.payload_size_ms * bytes_per_ms_),
+        kBaseTimestamp, true, bytes_per_ms_, samples_per_ms_);
+
+    EXPECT_EQ(expected_split.num_frames, results.size());
+    uint32_t expected_timestamp = kBaseTimestamp;
+    uint32_t expected_byte_offset = 0;
+    uint8_t value = 0;
+    for (size_t i = 0; i != expected_split.num_frames; ++i) {
+      const auto& result = results[i];
+      const LegacyEncodedAudioFrame* frame =
+          static_cast<const LegacyEncodedAudioFrame*>(result.frame.get());
+      const size_t length_bytes = expected_split.frame_sizes[i] * bytes_per_ms_;
+      EXPECT_EQ(length_bytes, frame->payload().size());
+      EXPECT_EQ(expected_timestamp, result.timestamp);
+      const rtc::Buffer& payload = frame->payload();
+      // Allow wrap-around of value in counter below.
+      for (size_t i = 0; i != payload.size(); ++i, ++value) {
+        ASSERT_EQ(value, payload[i]);
+      }
+
+      expected_timestamp += expected_split.frame_sizes[i] * samples_per_ms_;
+      expected_byte_offset += length_bytes;
+    }
+  }
+}
+
+INSTANTIATE_TEST_CASE_P(
+    LegacyEncodedAudioFrame,
+    SplitBySamplesTest,
+    ::testing::Values(NetEqDecoder::kDecoderPCMu,
+                      NetEqDecoder::kDecoderPCMa,
+                      NetEqDecoder::kDecoderPCMu_2ch,
+                      NetEqDecoder::kDecoderPCMa_2ch,
+                      NetEqDecoder::kDecoderG722,
+                      NetEqDecoder::kDecoderPCM16B,
+                      NetEqDecoder::kDecoderPCM16Bwb,
+                      NetEqDecoder::kDecoderPCM16Bswb32kHz,
+                      NetEqDecoder::kDecoderPCM16Bswb48kHz,
+                      NetEqDecoder::kDecoderPCM16B_2ch,
+                      NetEqDecoder::kDecoderPCM16Bwb_2ch,
+                      NetEqDecoder::kDecoderPCM16Bswb32kHz_2ch,
+                      NetEqDecoder::kDecoderPCM16Bswb48kHz_2ch,
+                      NetEqDecoder::kDecoderPCM16B_5ch));
+
+}  // namespace webrtc
diff --git a/webrtc/modules/audio_coding/codecs/pcm16b/audio_decoder_pcm16b.cc b/webrtc/modules/audio_coding/codecs/pcm16b/audio_decoder_pcm16b.cc
index dce5f4c..e600d2d 100644
--- a/webrtc/modules/audio_coding/codecs/pcm16b/audio_decoder_pcm16b.cc
+++ b/webrtc/modules/audio_coding/codecs/pcm16b/audio_decoder_pcm16b.cc
@@ -11,6 +11,7 @@
 #include "webrtc/modules/audio_coding/codecs/pcm16b/audio_decoder_pcm16b.h"
 
 #include "webrtc/base/checks.h"
+#include "webrtc/modules/audio_coding/codecs/legacy_encoded_audio_frame.h"
 #include "webrtc/modules/audio_coding/codecs/pcm16b/pcm16b.h"
 
 namespace webrtc {
@@ -44,6 +45,16 @@
   return static_cast<int>(ret);
 }
 
+std::vector<AudioDecoder::ParseResult> AudioDecoderPcm16B::ParsePayload(
+    rtc::Buffer&& payload,
+    uint32_t timestamp,
+    bool is_primary) {
+  const int samples_per_ms = rtc::CheckedDivExact(sample_rate_hz_, 1000);
+  return LegacyEncodedAudioFrame::SplitBySamples(
+      this, std::move(payload), timestamp, is_primary,
+      samples_per_ms * 2 * num_channels_, samples_per_ms);
+}
+
 int AudioDecoderPcm16B::PacketDuration(const uint8_t* encoded,
                                        size_t encoded_len) const {
   // Two encoded byte per sample per channel.
diff --git a/webrtc/modules/audio_coding/codecs/pcm16b/audio_decoder_pcm16b.h b/webrtc/modules/audio_coding/codecs/pcm16b/audio_decoder_pcm16b.h
index df94a6a..1d2da4a 100644
--- a/webrtc/modules/audio_coding/codecs/pcm16b/audio_decoder_pcm16b.h
+++ b/webrtc/modules/audio_coding/codecs/pcm16b/audio_decoder_pcm16b.h
@@ -20,6 +20,9 @@
  public:
   AudioDecoderPcm16B(int sample_rate_hz, size_t num_channels);
   void Reset() override;
+  std::vector<ParseResult> ParsePayload(rtc::Buffer&& payload,
+                                        uint32_t timestamp,
+                                        bool is_primary) override;
   int PacketDuration(const uint8_t* encoded, size_t encoded_len) const override;
   int SampleRateHz() const override;
   size_t Channels() const override;
diff --git a/webrtc/modules/audio_coding/codecs/pcm16b/pcm16b.gypi b/webrtc/modules/audio_coding/codecs/pcm16b/pcm16b.gypi
index d0dd21b..ae40793 100644
--- a/webrtc/modules/audio_coding/codecs/pcm16b/pcm16b.gypi
+++ b/webrtc/modules/audio_coding/codecs/pcm16b/pcm16b.gypi
@@ -13,6 +13,8 @@
       'type': 'static_library',
       'dependencies': [
         'audio_encoder_interface',
+        'audio_decoder_interface',
+        'legacy_encoded_audio_frame',
         'g711',
       ],
       'sources': [