diff --git a/libavcodec/common.h b/libavcodec/common.h
index 169e15e124..ef66954002 100644
--- a/libavcodec/common.h
+++ b/libavcodec/common.h
@@ -281,6 +281,7 @@ struct PutBitContext;
 
 typedef void (*WriteDataFunc)(void *, uint8_t *, int);
 
+/* buf and buf_end must be present and used by every alternative writer. */
 typedef struct PutBitContext {
 #ifdef ALT_BITSTREAM_WRITER
     uint8_t *buf, *buf_end;
@@ -317,11 +318,6 @@ static inline int put_bits_count(PutBitContext *s)
 #endif
 }
 
-static inline int put_bits_left(PutBitContext* s)
-{
-    return (s->buf_end - s->buf) * 8 - put_bits_count(s);
-}
-
 /* pad the end of the output stream with zeros */
 static inline void flush_put_bits(PutBitContext *s)
 {
@@ -344,7 +340,7 @@ void align_put_bits(PutBitContext *s);
 void put_string(PutBitContext * pbc, char *s, int put_zero);
 
 /* bit input */
-
+/* buffer, buffer_end and size_in_bits must be present and used by every reader */
 typedef struct GetBitContext {
     const uint8_t *buffer, *buffer_end;
 #ifdef ALT_BITSTREAM_READER
@@ -914,16 +910,6 @@ static inline void init_get_bits(GetBitContext *s,
 #endif
 }
 
-static inline int get_bits_left(GetBitContext *s)
-{
-    return s->size_in_bits - get_bits_count(s);
-}
-
-static inline int get_bits_size(GetBitContext *s)
-{
-    return s->size_in_bits;
-}
-
 int check_marker(GetBitContext *s, const char *msg);
 void align_get_bits(GetBitContext *s);
 int init_vlc(VLC *vlc, int nb_bits, int nb_codes,
diff --git a/libavcodec/dv.c b/libavcodec/dv.c
index 45f68e2a69..6b7ca1d8d2 100644
--- a/libavcodec/dv.c
+++ b/libavcodec/dv.c
@@ -240,6 +240,21 @@ static const int mb_area_start[5] = { 1, 6, 21, 43, 64 };
 #warning only works with ALT_BITSTREAM_READER
 #endif
 
+static inline int get_bits_left(GetBitContext *s)
+{
+    return s->size_in_bits - get_bits_count(s);
+}
+
+static inline int get_bits_size(GetBitContext *s)
+{
+    return s->size_in_bits;
+}
+
+static inline int put_bits_left(PutBitContext* s)
+{
+    return (s->buf_end - s->buf) * 8 - put_bits_count(s);
+}
+
 /* decode ac coefs */
 static void dv_decode_ac(GetBitContext *gb, BlockInfo *mb, DCTELEM *block)
 {