From 9ed471651efff7fe7c0b59b45057d95e37fe0689 Mon Sep 17 00:00:00 2001
From: olly <olly@google.com>
Date: Tue, 24 Mar 2020 15:32:52 +0000
Subject: [PATCH] Support 32-bit FP to 16-bit Int audio resampling

This is a no-op for DefaultAudioSink for now, because DefaultAudioSink
currently disables processing anyway if the input uses ENCODING_PCM_FLOAT.

Issue: #7134
PiperOrigin-RevId: 302670534
---
 .../audio/ResamplingAudioProcessor.java       | 28 +++++++++++++++----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/library/core/src/main/java/com/google/android/exoplayer2/audio/ResamplingAudioProcessor.java b/library/core/src/main/java/com/google/android/exoplayer2/audio/ResamplingAudioProcessor.java
index 7175b93614..883f5bcb92 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/audio/ResamplingAudioProcessor.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/audio/ResamplingAudioProcessor.java
@@ -20,8 +20,17 @@ import com.google.android.exoplayer2.Format;
 import java.nio.ByteBuffer;
 
 /**
- * An {@link AudioProcessor} that converts 8-bit, 24-bit and 32-bit integer PCM audio to 16-bit
- * integer PCM audio.
+ * An {@link AudioProcessor} that converts different PCM audio encodings to 16-bit integer PCM. The
+ * following encodings are supported as input:
+ *
+ * <ul>
+ *   <li>{@link C#ENCODING_PCM_8BIT}
+ *   <li>{@link C#ENCODING_PCM_16BIT} ({@link #isActive()} will return {@code false})
+ *   <li>{@link C#ENCODING_PCM_16BIT_BIG_ENDIAN}
+ *   <li>{@link C#ENCODING_PCM_24BIT}
+ *   <li>{@link C#ENCODING_PCM_32BIT}
+ *   <li>{@link C#ENCODING_PCM_FLOAT}
+ * </ul>
  */
 /* package */ final class ResamplingAudioProcessor extends BaseAudioProcessor {
 
@@ -33,7 +42,8 @@ import java.nio.ByteBuffer;
         && encoding != C.ENCODING_PCM_16BIT
         && encoding != C.ENCODING_PCM_16BIT_BIG_ENDIAN
         && encoding != C.ENCODING_PCM_24BIT
-        && encoding != C.ENCODING_PCM_32BIT) {
+        && encoding != C.ENCODING_PCM_32BIT
+        && encoding != C.ENCODING_PCM_FLOAT) {
       throw new UnhandledAudioFormatException(inputAudioFormat);
     }
     return encoding != C.ENCODING_PCM_16BIT
@@ -60,10 +70,10 @@ import java.nio.ByteBuffer;
         resampledSize = (size / 3) * 2;
         break;
       case C.ENCODING_PCM_32BIT:
+      case C.ENCODING_PCM_FLOAT:
         resampledSize = size / 2;
         break;
       case C.ENCODING_PCM_16BIT:
-      case C.ENCODING_PCM_FLOAT:
       case C.ENCODING_INVALID:
       case Format.NO_VALUE:
       default:
@@ -101,8 +111,16 @@ import java.nio.ByteBuffer;
           buffer.put(inputBuffer.get(i + 3));
         }
         break;
-      case C.ENCODING_PCM_16BIT:
       case C.ENCODING_PCM_FLOAT:
+        // 32 bit floating point -> 16 bit resampling. Floating point values are in the range
+        // [-1.0, 1.0], so need to be scaled by Short.MAX_VALUE.
+        for (int i = position; i < limit; i += 4) {
+          short value = (short) (inputBuffer.getFloat(i) * Short.MAX_VALUE);
+          buffer.put((byte) (value & 0xFF));
+          buffer.put((byte) ((value >> 8) & 0xFF));
+        }
+        break;
+      case C.ENCODING_PCM_16BIT:
       case C.ENCODING_INVALID:
       case Format.NO_VALUE:
       default: