From cf90d2624d114cdd3cbc8516565409dd8bd48cb7 Mon Sep 17 00:00:00 2001
From: Googler <noreply@google.com>
Date: Wed, 10 Jul 2024 05:13:18 -0700
Subject: [PATCH] Support for Large CodecSpecificData in ESDS box

Some external media files have CodecSpecificData greater than 128 bytes. Currently, that size
isn't fitting in one byte. Hence, added support to store large CodecSpecificDataSize, as per
ISO standard, by extending to more than one byte as required.

PiperOrigin-RevId: 650972472
---
 .../java/androidx/media3/muxer/Boxes.java     | 52 +++++++++++++------
 1 file changed, 35 insertions(+), 17 deletions(-)

diff --git a/libraries/muxer/src/main/java/androidx/media3/muxer/Boxes.java b/libraries/muxer/src/main/java/androidx/media3/muxer/Boxes.java
index ca4f1087d4..9bc10cb89c 100644
--- a/libraries/muxer/src/main/java/androidx/media3/muxer/Boxes.java
+++ b/libraries/muxer/src/main/java/androidx/media3/muxer/Boxes.java
@@ -39,6 +39,7 @@ import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 import com.google.common.primitives.Bytes;
 import java.nio.ByteBuffer;
+import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -1343,37 +1344,37 @@ import java.util.List;
     ByteBuffer csd0ByteBuffer = ByteBuffer.wrap(csd0);
     int peakBitrate = format.peakBitrate;
     int averageBitrate = format.averageBitrate;
+
     int csd0Size = csd0ByteBuffer.limit();
+    ByteBuffer dsiSizeBuffer = getSizeBuffer(csd0Size);
+    ByteBuffer dcdSizeBuffer = getSizeBuffer(csd0Size + dsiSizeBuffer.remaining() + 14);
+    ByteBuffer esdSizeBuffer =
+        getSizeBuffer(csd0Size + dsiSizeBuffer.remaining() + dcdSizeBuffer.remaining() + 21);
 
     ByteBuffer contents = ByteBuffer.allocate(csd0Size + MAX_FIXED_LEAF_BOX_SIZE);
-    contents.putInt(0x0); // version and flags.
+    contents.putInt(0x00); // Version and flags.
     contents.put((byte) 0x03); // ES_DescrTag
 
-    // We're normally using a variable-length encoding for the length of various sub-packages (esds
-    // etc.), in a nested way, so outer lengths need to account for variable-length inner lengths
-    // too (to save ~10 bytes per video file). Meanwhile, AAC codec-specific
-    // data is typically just 2 bytes, so every length actually fits into a byte. Here, we're just
-    // skipping the entire complex story by asserting that we won't ever need variable-length sizes.
-    checkArgument(csd0Size + 21 < 127, "CSD too long; we might need variable-length encoding?");
+    contents.put(esdSizeBuffer);
 
-    contents.put((byte) (23 + csd0Size));
-
-    contents.putShort((short) 0x0000); // ES_ID
-    contents.put((byte) 0x00);
+    contents.putShort((short) 0x0000); // First 16 bits of ES_ID.
+    contents.put((byte) 0x00); // Last 8 bits of ES_ID.
 
     contents.put((byte) 0x04); // DecoderConfigDescrTag
-    contents.put((byte) (15 + csd0Size));
-    contents.put((byte) 0x40); // objectTypeIndication
-    contents.put((byte) 0x15); // streamType AudioStream
+    contents.put(dcdSizeBuffer);
 
-    contents.putShort((short) 0x03);
-    contents.put((byte) 0x00); // 24-bit buffer size (0x300)
+    contents.put((byte) 0x40); // objectTypeIndication
+    // streamType (6 bits) | upStream (1 bit) | reserved = 1 (1 bit)
+    contents.put((byte) ((0x05 << 2) | 0x01)); // streamType AudioStream
+
+    contents.putShort((short) 0x03); // First 16 bits of buffer size (0x300).
+    contents.put((byte) 0x00); // Last 8 bits of buffer size (0x300).
 
     contents.putInt(peakBitrate != Format.NO_VALUE ? peakBitrate : 0);
     contents.putInt(averageBitrate != Format.NO_VALUE ? averageBitrate : 0);
 
     contents.put((byte) 0x05); // DecoderSpecificInfoTag
-    contents.put((byte) csd0Size);
+    contents.put(dsiSizeBuffer);
     contents.put(csd0ByteBuffer);
     csd0ByteBuffer.rewind();
 
@@ -1385,6 +1386,23 @@ import java.util.List;
     return BoxUtils.wrapIntoBox("esds", contents);
   }
 
+  private static ByteBuffer getSizeBuffer(int length) {
+    int prefix = 0;
+    ArrayDeque<Byte> esdsSizeBytes = new ArrayDeque<>();
+    do {
+      esdsSizeBytes.push((byte) (prefix | (length & 0x7F)));
+      length >>= 7;
+      prefix = 0x80;
+    } while (length > 0);
+
+    ByteBuffer sizeBuffer = ByteBuffer.allocate(esdsSizeBytes.size());
+    while (!esdsSizeBytes.isEmpty()) {
+      sizeBuffer.put(esdsSizeBytes.removeFirst());
+    }
+    sizeBuffer.flip();
+    return sizeBuffer;
+  }
+
   /** Returns the audio damr box. */
   private static ByteBuffer damrBox(short mode) {