diff --git a/libavcodec/common.c b/libavcodec/common.c
index 22031a2a98..8c50fbc8d6 100644
--- a/libavcodec/common.c
+++ b/libavcodec/common.c
@@ -123,6 +123,12 @@ void put_string(PutBitContext * pbc, char *s)
 
 #endif //CONFIG_ENCODERS
 
+/**
+ * init GetBitContext.
+ * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
+ * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
+ * @param bit_size the size of the buffer in bits
+ */
 void init_get_bits(GetBitContext *s,
                    const uint8_t *buffer, int bit_size)
 {
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index a422cf282d..01d945b997 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -343,9 +343,15 @@ int avcodec_encode_video(AVCodecContext *avctx, uint8_t *buf, int buf_size,
     return ret;
 }
 
-/* decode a frame. return -1 if error, otherwise return the number of
-   bytes used. If no frame could be decompressed, *got_picture_ptr is
-   zero. Otherwise, it is non zero */
+/** 
+ * decode a frame. 
+ * @param buf bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE larger then the actual read bytes
+ * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
+ * @param buf_size the size of the buffer in bytes
+ * @param got_picture_ptr zero if no frame could be decompressed, Otherwise, it is non zero
+ * @return -1 if error, otherwise return the number of
+ * bytes used. 
+ */
 int avcodec_decode_video(AVCodecContext *avctx, AVFrame *picture, 
                          int *got_picture_ptr,
                          uint8_t *buf, int buf_size)