--- a/dom/media/platforms/wrappers/H264Converter.cpp
+++ b/dom/media/platforms/wrappers/H264Converter.cpp
@@ -160,16 +160,19 @@ H264Converter::CreateDecoderAndInit(Medi
     return NS_ERROR_NOT_INITIALIZED;
   }
   UpdateConfigFromExtraData(extra_data);
 
   nsresult rv = CreateDecoder();
 
   if (NS_SUCCEEDED(rv)) {
     mDecoderInitializing = true;
+    // Queue the incoming sample.
+    mMediaRawSamples.AppendElement(aSample);
+
     nsRefPtr<H264Converter> self = this;
 
     // The mVideoTaskQueue is flushable which can't be used in MediaPromise. So
     // we get the current AbstractThread instead of it. The MOZ_ASSERT above
     // ensures we are running in AbstractThread so we won't get a nullptr.
     mInitPromiseRequest.Begin(mDecoder->Init()
       ->Then(AbstractThread::GetCurrent(), __func__, this,
              &H264Converter::OnDecoderInitDone,