Fixing NetEqReplacementInput for reordered and missing packets

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

Index: webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.cc
diff --git a/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.cc b/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.cc
index d5bd97d45943dcec00cbcf6476a29f4f6a38aa00..c9163a15d8b993b3ea24562df252fc97c8bd3349 100644
--- a/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.cc
+++ b/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.cc
@@ -85,12 +85,12 @@ void NetEqReplacementInput::ReplacePacket() {
   rtc::Optional<RTPHeader> next_hdr = source_->NextHeader();
   RTC_DCHECK(next_hdr);
   uint8_t payload[12];
-  uint32_t input_frame_size_timestamps =
-      next_hdr->timestamp - packet_->header.header.timestamp;
-  if (next_hdr->sequenceNumber != packet_->header.header.sequenceNumber + 1) {
-    // Gap in packet sequence. Cannot estimate payload length based on timestamp
-    // difference.
-    input_frame_size_timestamps = 0;
+  uint32_t input_frame_size_timestamps = last_frame_size_timestamps_;
+  if (next_hdr->sequenceNumber == packet_->header.header.sequenceNumber + 1) {
+    // Packets are in order.
+    input_frame_size_timestamps =
+        next_hdr->timestamp - packet_->header.header.timestamp;
+    last_frame_size_timestamps_ = input_frame_size_timestamps;
   }
   FakeDecodeFromFile::PrepareEncoded(packet_->header.header.timestamp,
                                      input_frame_size_timestamps,