+/**
+ * Maximum size in bytes of extradata.
+ * This value was chosen such that every bit of the buffer is
+ * addressable by a 32-bit signed integer as used by get_bits.
+ */
+#define FF_MAX_EXTRADATA_SIZE ((1 << 28) - FF_INPUT_BUFFER_PADDING_SIZE)
+
+/**
+ * Check AVPacket size and/or allocate data.
+ *
+ * Encoders supporting AVCodec.encode2() can use this as a convenience to
+ * ensure the output packet data is large enough, whether provided by the user
+ * or allocated in this function.
+ *
+ * @param avpkt the AVPacket
+ * If avpkt->data is already set, avpkt->size is checked
+ * to ensure it is large enough.
+ * If avpkt->data is NULL, a new buffer is allocated.
+ * avpkt->size is set to the specified size.
+ * All other AVPacket fields will be reset with av_init_packet().
+ * @param size the minimum required packet size
+ * @return 0 on success, negative error code on failure
+ */
+int ff_alloc_packet(AVPacket *avpkt, int size);
+