1 files changed, 69 insertions, 0 deletions
diff --git a/libs/android-transcoder/src/main/java/net/ypresto/androidtranscoder/utils/AvcCsdUtils.java b/libs/android-transcoder/src/main/java/net/ypresto/androidtranscoder/utils/AvcCsdUtils.java
new file mode 100644
index 000000000..049296b9b
--- /dev/null
+++ b/libs/android-transcoder/src/main/java/net/ypresto/androidtranscoder/utils/AvcCsdUtils.java
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2015 Yuya Tanaka
+ *
+ * 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 net.ypresto.androidtranscoder.utils;
+
+import android.media.MediaFormat;
+
+import net.ypresto.androidtranscoder.format.MediaFormatExtraConstants;
+
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+
+public class AvcCsdUtils {
+    // Refer: https://android.googlesource.com/platform/frameworks/av/+/lollipop-release/media/libstagefright/MediaCodec.cpp#2198
+    // Refer: http://stackoverflow.com/a/2861340
+    private static final byte[] AVC_START_CODE_3 = {0x00, 0x00, 0x01};
+    private static final byte[] AVC_START_CODE_4 = {0x00, 0x00, 0x00, 0x01};
+    // Refer: http://www.cardinalpeak.com/blog/the-h-264-sequence-parameter-set/
+    private static final byte AVC_SPS_NAL = 103; // 0<<7 + 3<<5 + 7<<0
+    // https://tools.ietf.org/html/rfc6184
+    private static final byte AVC_SPS_NAL_2 = 39; // 0<<7 + 1<<5 + 7<<0
+    private static final byte AVC_SPS_NAL_3 = 71; // 0<<7 + 2<<5 + 7<<0
+
+    /**
+     * @return ByteBuffer contains SPS without NAL header.
+     */
+    public static ByteBuffer getSpsBuffer(MediaFormat format) {
+        ByteBuffer sourceBuffer = format.getByteBuffer(MediaFormatExtraConstants.KEY_AVC_SPS).asReadOnlyBuffer(); // might be direct buffer
+        ByteBuffer prefixedSpsBuffer = ByteBuffer.allocate(sourceBuffer.limit()).order(sourceBuffer.order());
+        prefixedSpsBuffer.put(sourceBuffer);
+        prefixedSpsBuffer.flip();
+
+        skipStartCode(prefixedSpsBuffer);
+
+        byte spsNalData = prefixedSpsBuffer.get();
+        if (spsNalData != AVC_SPS_NAL && spsNalData != AVC_SPS_NAL_2 && spsNalData != AVC_SPS_NAL_3) {
+            throw new IllegalStateException("Got non SPS NAL data.");
+        }
+
+        return prefixedSpsBuffer.slice();
+    }
+
+    private static void skipStartCode(ByteBuffer prefixedSpsBuffer) {
+        byte[] prefix3 = new byte[3];
+        prefixedSpsBuffer.get(prefix3);
+        if (Arrays.equals(prefix3, AVC_START_CODE_3)) return;
+
+        byte[] prefix4 = Arrays.copyOf(prefix3, 4);
+        prefix4[3] = prefixedSpsBuffer.get();
+        if (Arrays.equals(prefix4, AVC_START_CODE_4)) return;
+        throw new IllegalStateException("AVC NAL start code does not found in csd.");
+    }
+
+    private AvcCsdUtils() {
+        throw new RuntimeException();
+    }
+}