From aadcbe332bf88543a9d065b9251c586a93b893fe Mon Sep 17 00:00:00 2001
From: dancho <dancho@google.com>
Date: Tue, 28 May 2024 03:57:19 -0700
Subject: [PATCH] Ensure single-frame videos are correctly exported

Add a wait in DefaultCodec.signalEndOfInputStream when no
video encoder output has been seen. This avoids a thread synchronization problem
between writing frames to video surface, and signaling end of stream,
which was hit for video input of only one frame on some devices.

PiperOrigin-RevId: 637844690
---
 .../media3/transformer/DefaultCodec.java      | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/DefaultCodec.java b/libraries/transformer/src/main/java/androidx/media3/transformer/DefaultCodec.java
index 57f2e498a2..8275dbebf3 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/DefaultCodec.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/DefaultCodec.java
@@ -52,6 +52,7 @@ import androidx.media3.effect.DebugTraceUtil;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.Objects;
+import java.util.concurrent.atomic.AtomicBoolean;
 import org.checkerframework.checker.initialization.qual.UnknownInitialization;
 import org.checkerframework.checker.nullness.qual.EnsuresNonNullIf;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
@@ -76,6 +77,9 @@ public final class DefaultCodec implements Codec {
   private final int maxPendingFrameCount;
   private final boolean isDecoder;
   private final boolean isVideo;
+  // Accessed concurrently by playback thread when reading output, and video effects thread
+  // when signaling end of stream.
+  private final AtomicBoolean videoOutputStarted;
 
   private @MonotonicNonNull Format outputFormat;
   @Nullable private ByteBuffer outputBuffer;
@@ -112,6 +116,7 @@ public final class DefaultCodec implements Codec {
     outputBufferInfo = new BufferInfo();
     inputBufferIndex = C.INDEX_UNSET;
     outputBufferIndex = C.INDEX_UNSET;
+    videoOutputStarted = new AtomicBoolean();
     DebugTraceUtil.logCodecEvent(
         isDecoder, isVideo, EVENT_INPUT_FORMAT, C.TIME_UNSET, "%s", configurationFormat);
 
@@ -248,6 +253,17 @@ public final class DefaultCodec implements Codec {
 
   @Override
   public void signalEndOfInputStream() throws ExportException {
+    if (!videoOutputStarted.get()) {
+      // When encoding a 1-frame video, there is a synchronization problem between feeding the frame
+      // to the encoder input surface and signaling end of stream. On some devices, sometimes,
+      // the frame gets lost and an empty output is produced. Waiting before signaling end of stream
+      // seems to resolve this issue. See b/301603935.
+      try {
+        Thread.sleep(10);
+      } catch (InterruptedException e) {
+        Thread.currentThread().interrupt();
+      }
+    }
     debugTraceLogEvent(EVENT_INPUT_ENDED, C.TIME_END_OF_SOURCE);
     try {
       mediaCodec.signalEndOfInputStream();
@@ -387,6 +403,9 @@ public final class DefaultCodec implements Codec {
                   .setPcmEncoding(configurationFormat.pcmEncoding)
                   .build();
         }
+        if (!isDecoder && isVideo) {
+          videoOutputStarted.set(true);
+        }
         debugTraceLogEvent(
             EVENT_OUTPUT_FORMAT, outputBufferInfo.presentationTimeUs, "%s", outputFormat);
       }