Do not forward the audio codec config buffer as an encoded frame

encoder/src/main/java/com/pedro/encoder/audio/AudioEncoder.java

@@ -167,6 +167,11 @@ protected long calculatePts(Frame frame, long presentTimeUs) {
   @Override
   protected boolean checkBuffer(@NonNull ByteBuffer byteBuffer,
       @NonNull MediaCodec.BufferInfo bufferInfo) {
+    // Codec config (e.g. AAC AudioSpecificConfig) is signalled per protocol and via
+    // MediaFormat csd-0 for the muxer; do not forward it as an encoded audio frame.
+    if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
+      return false;
+    }
     return checkValidTimeStamp(bufferInfo);
   }
 

encoder/src/test/java/com/pedro/encoder/AudioEncoderCheckBufferTest.kt

@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2024 pedroSG94.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.pedro.encoder
+
+import android.media.MediaCodec
+import android.media.MediaFormat
+import com.pedro.encoder.audio.AudioEncoder
+import com.pedro.encoder.audio.GetAudioData
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import java.nio.ByteBuffer
+
+class AudioEncoderCheckBufferTest {
+
+  private val encoder = object : AudioEncoder(NO_OP_AUDIO_DATA) {
+    fun acceptsBuffer(bufferInfo: MediaCodec.BufferInfo): Boolean {
+      return checkBuffer(ByteBuffer.allocate(bufferInfo.size), bufferInfo)
+    }
+  }
+
+  @Test
+  fun `WHEN buffer has codec config flag THEN checkBuffer rejects it`() {
+    val bufferInfo = MediaCodec.BufferInfo().apply {
+      offset = 0
+      size = 2
+      presentationTimeUs = 0
+      flags = MediaCodec.BUFFER_FLAG_CODEC_CONFIG
+    }
+    assertFalse(encoder.acceptsBuffer(bufferInfo))
+  }
+
+  @Test
+  fun `WHEN buffer is a normal encoded frame THEN checkBuffer accepts valid timestamp`() {
+    val bufferInfo = MediaCodec.BufferInfo().apply {
+      offset = 0
+      size = 256
+      presentationTimeUs = 1_000
+      flags = 0
+    }
+    assertTrue(encoder.acceptsBuffer(bufferInfo))
+  }
+
+  private companion object {
+    private val NO_OP_AUDIO_DATA = object : GetAudioData {
+      override fun getAudioData(byteBuffer: ByteBuffer, bufferInfo: MediaCodec.BufferInfo) {}
+      override fun onAudioFormat(mediaFormat: MediaFormat) {}
+    }
+  }
+}