diff --git a/libav/asf.c b/libav/asf.c
index 4f82e65fa1..892d863c6f 100644
--- a/libav/asf.c
+++ b/libav/asf.c
@@ -874,7 +874,7 @@ static int asf_read_header(AVFormatContext *s, AVFormatParameters *ap)
 		    st->codec.extradata = av_mallocz(st->codec.extradata_size);
 		    get_buffer(pb, st->codec.extradata, st->codec.extradata_size);
 		}
-                st->codec.codec_tag = tag1;
+                st->codec.codec_tag = st->codec.fourcc = tag1;
 		st->codec.codec_id = codec_get_id(codec_bmp_tags, tag1);
             }
             pos2 = url_ftell(pb);
@@ -1202,7 +1202,7 @@ static int asf_read_seek(AVFormatContext *s, int64_t pts)
     return -1;
 }
 
-AVInputFormat asf_iformat = {
+static AVInputFormat asf_iformat = {
     "asf",
     "asf format",
     sizeof(ASFContext),
@@ -1213,7 +1213,7 @@ AVInputFormat asf_iformat = {
     asf_read_seek,
 };
 
-AVOutputFormat asf_oformat = {
+static AVOutputFormat asf_oformat = {
     "asf",
     "asf format",
     "application/octet-stream",
@@ -1230,7 +1230,7 @@ AVOutputFormat asf_oformat = {
     asf_write_trailer,
 };
 
-AVOutputFormat asf_stream_oformat = {
+static AVOutputFormat asf_stream_oformat = {
     "asf_stream",
     "asf format",
     "application/octet-stream",
diff --git a/libav/avienc.c b/libav/avienc.c
index 27c8ac753f..2270f8453e 100644
--- a/libav/avienc.c
+++ b/libav/avienc.c
@@ -36,7 +36,7 @@ typedef struct {
     AVIIndex *first, *last;
 } AVIContext;
 
-offset_t start_tag(ByteIOContext *pb, char *tag)
+offset_t start_tag(ByteIOContext *pb, const char *tag)
 {
     put_tag(pb, tag);
     put_le32(pb, 0);
@@ -55,7 +55,7 @@ void end_tag(ByteIOContext *pb, offset_t start)
 
 /* Note: when encoding, the first matching tag is used, so order is
    important if multiple tags possible for a given codec. */
-CodecTag codec_bmp_tags[] = {
+const CodecTag codec_bmp_tags[] = {
     { CODEC_ID_H263, MKTAG('H', '2', '6', '3') },
     { CODEC_ID_H263P, MKTAG('H', '2', '6', '3') },
     { CODEC_ID_H263I, MKTAG('I', '2', '6', '3') }, /* intel h263 */
@@ -122,7 +122,7 @@ unsigned int codec_get_bmp_tag(int id)
 }
 
 /* BITMAPINFOHEADER header */
-void put_bmp_header(ByteIOContext *pb, AVCodecContext *enc, CodecTag *tags, int for_asf)
+void put_bmp_header(ByteIOContext *pb, AVCodecContext *enc, const CodecTag *tags, int for_asf)
 {
     put_le32(pb, 40); /* size */
     put_le32(pb, enc->width);
@@ -138,7 +138,7 @@ void put_bmp_header(ByteIOContext *pb, AVCodecContext *enc, CodecTag *tags, int
     put_le32(pb, 0);
 }
 
-void parse_specific_params(AVCodecContext *stream, int *au_byterate, int *au_ssize, int *au_scale)
+static void parse_specific_params(AVCodecContext *stream, int *au_byterate, int *au_ssize, int *au_scale)
 {
     switch(stream->codec_id) {
     case CODEC_ID_PCM_S16LE:
diff --git a/libav/avio.h b/libav/avio.h
index bf00f2edd1..541eff5ae0 100644
--- a/libav/avio.h
+++ b/libav/avio.h
@@ -85,7 +85,7 @@ void put_le32(ByteIOContext *s, unsigned int val);
 void put_be32(ByteIOContext *s, unsigned int val);
 void put_le16(ByteIOContext *s, unsigned int val);
 void put_be16(ByteIOContext *s, unsigned int val);
-void put_tag(ByteIOContext *s, char *tag);
+void put_tag(ByteIOContext *s, const char *tag);
 
 void put_be64_double(ByteIOContext *s, double val);
 void put_strz(ByteIOContext *s, const char *buf);
diff --git a/libav/aviobuf.c b/libav/aviobuf.c
index 27f6b5d38a..2e931bd849 100644
--- a/libav/aviobuf.c
+++ b/libav/aviobuf.c
@@ -219,7 +219,7 @@ void put_be16(ByteIOContext *s, unsigned int val)
     put_byte(s, val);
 }
 
-void put_tag(ByteIOContext *s, char *tag)
+void put_tag(ByteIOContext *s, const char *tag)
 {
     while (*tag) {
         put_byte(s, *tag++);