Make FakeDecodeFromFile handle codec-internal CNG

webrtc/modules/audio_coding/neteq/tools/fake_decode_from_file.cc

Index: webrtc/modules/audio_coding/neteq/tools/fake_decode_from_file.cc
diff --git a/webrtc/modules/audio_coding/neteq/tools/fake_decode_from_file.cc b/webrtc/modules/audio_coding/neteq/tools/fake_decode_from_file.cc
index 9ca5fb810bd64f21298680634793cc1b53a55ae5..29beed5644f31402bda6d74d75fde25b676d4ab3 100644
--- a/webrtc/modules/audio_coding/neteq/tools/fake_decode_from_file.cc
+++ b/webrtc/modules/audio_coding/neteq/tools/fake_decode_from_file.cc
@@ -19,14 +19,37 @@ namespace test {
 
 int FakeDecodeFromFile::DecodeInternal(const uint8_t* encoded,
                                        size_t encoded_len,
-                                       int /*sample_rate_hz*/,
+                                       int sample_rate_hz,
                                        int16_t* decoded,
                                        SpeechType* speech_type) {
-  RTC_CHECK_GE(encoded_len, 8u);
+  if (encoded_len == 0) {
+    // Decoder is asked to produce codec-internal comfort noise.
+    RTC_DCHECK(!encoded);  // NetEq always sends nullptr in this case.
+    RTC_DCHECK(cng_mode_);
+    RTC_DCHECK_GT(last_decoded_length_, 0u);
+    std::fill_n(decoded, last_decoded_length_, 0);
+    *speech_type = kComfortNoise;
+    return last_decoded_length_;
+  }
+
+  RTC_CHECK_GE(encoded_len, 12u);
   uint32_t timestamp_to_decode =
       ByteReader<uint32_t>::ReadLittleEndian(encoded);
   uint32_t samples_to_decode =
       ByteReader<uint32_t>::ReadLittleEndian(&encoded[4]);
+  if (samples_to_decode == 0) {
+    // Number of samples in packet is unknown.
+    if (last_decoded_length_ > 0) {
+      // Use length of last decoded packet, but since this is the total for all
+      // channels, we have to divide by 2 in the stereo case.
+      samples_to_decode = rtc::CheckedDivExact(
+          last_decoded_length_, static_cast<size_t>(stereo_ ? 2uL : 1uL));
+    } else {
+      // This is the first packet to decode, and we do not know the length of
+      // it. Set it to 10 ms.
+      samples_to_decode = rtc::CheckedDivExact(sample_rate_hz, 100);
+    }
+  }
 
   if (next_timestamp_from_input_ &&
       timestamp_to_decode != *next_timestamp_from_input_) {
@@ -36,10 +59,23 @@ int FakeDecodeFromFile::DecodeInternal(const uint8_t* encoded,
     RTC_CHECK(input_->Seek(jump));
   }
 
-  RTC_CHECK(input_->Read(static_cast<size_t>(samples_to_decode), decoded));
   next_timestamp_from_input_ =
       rtc::Optional<uint32_t>(timestamp_to_decode + samples_to_decode);
 
+  uint32_t original_payload_size_bytes =
+      ByteReader<uint32_t>::ReadLittleEndian(&encoded[8]);
+  if (original_payload_size_bytes == 1) {
+    // This is a comfort noise payload.
+    RTC_DCHECK_GT(last_decoded_length_, 0u);
+    std::fill_n(decoded, last_decoded_length_, 0);
+    *speech_type = kComfortNoise;
+    cng_mode_ = true;
+    return last_decoded_length_;
+  }
+
+  cng_mode_ = false;
+  RTC_CHECK(input_->Read(static_cast<size_t>(samples_to_decode), decoded));
+
   if (stereo_) {
     InputAudioFile::DuplicateInterleaved(decoded, samples_to_decode, 2,
                                          decoded);
@@ -47,16 +83,19 @@ int FakeDecodeFromFile::DecodeInternal(const uint8_t* encoded,
   }
 
   *speech_type = kSpeech;
-  return samples_to_decode;
+  return last_decoded_length_ = samples_to_decode;
 }
 
 void FakeDecodeFromFile::PrepareEncoded(uint32_t timestamp,
                                         size_t samples,
+                                        size_t original_payload_size_bytes,
                                         rtc::ArrayView<uint8_t> encoded) {
-  RTC_CHECK_GE(encoded.size(), 8u);
+  RTC_CHECK_GE(encoded.size(), 12u);
   ByteWriter<uint32_t>::WriteLittleEndian(&encoded[0], timestamp);
   ByteWriter<uint32_t>::WriteLittleEndian(&encoded[4],
                                           rtc::checked_cast<uint32_t>(samples));
+  ByteWriter<uint32_t>::WriteLittleEndian(
+      &encoded[8], rtc::checked_cast<uint32_t>(original_payload_size_bytes));
 }
 
 }  // namespace test