Use streaminfo block for FLAC files.

Some files do not have the sample size in each frame headers, in that case, ffmpeg needs the streaminfo data to properly decode them.

Author: Tolriq

libraries/decoder_ffmpeg/src/main/java/androidx/media3/decoder/ffmpeg/FfmpegAudioDecoder.java

@@ -190,12 +190,57 @@ private static byte[] getExtraData(String mimeType, List<byte[]> initializationD
         return getAlacExtraData(initializationData);
       case MimeTypes.AUDIO_VORBIS:
         return getVorbisExtraData(initializationData);
+      case MimeTypes.AUDIO_FLAC:
+        return getFlacExtraData(initializationData);
       default:
         // Other codecs do not require extra data.
         return null;
     }
   }
 
+  @Nullable
+  private static byte[] getFlacExtraData(List<byte[]> initializationData) {
+    for (int i = 0; i < initializationData.size(); i++) {
+      byte[] out = extractFlacStreamInfo(initializationData.get(i));
+      if (out != null) {
+        return out;
+      }
+    }
+    return null;
+  }
+
+  @Nullable
+  private static byte[] extractFlacStreamInfo(byte[] data) {
+    final int STREAMINFO_LEN = 34;
+    int off = 0;
+
+    if (data.length >= 4
+        && data[0] == (byte) 'f'
+        && data[1] == (byte) 'L'
+        && data[2] == (byte) 'a'
+        && data[3] == (byte) 'C') {
+      off = 4;
+    }
+
+    if (data.length - off == STREAMINFO_LEN) {
+      byte[] out = new byte[STREAMINFO_LEN];
+      System.arraycopy(data, off, out, 0, STREAMINFO_LEN);
+      return out;
+    }
+
+    if (data.length >= off + 4) {
+      int type = data[off] & 0x7F;
+      int len = ((data[off + 1] & 0xFF) << 16) | ((data[off + 2] & 0xFF) << 8) | (data[off + 3] & 0xFF);
+      if (type == 0 && len == STREAMINFO_LEN && data.length >= off + 4 + STREAMINFO_LEN) {
+        byte[] out = new byte[STREAMINFO_LEN];
+        System.arraycopy(data, off + 4, out, 0, STREAMINFO_LEN);
+        return out;
+      }
+    }
+
+    return null;
+  }
+
   private static byte[] getAlacExtraData(List<byte[]> initializationData) {
     // FFmpeg's ALAC decoder expects an ALAC atom, which contains the ALAC "magic cookie", as extra
     // data. initializationData[0] contains only the magic cookie, and so we need to package it into