lavf/sdp: add const qualifiers where appropriate

Declares that these structs are read-only for this code.

libavformat/internal.h

@@ -557,7 +557,7 @@ uint64_t ff_parse_ntp_time(uint64_t ntp_ts);
  * @param fmt the AVFormatContext, which might contain options modifying
  *            the generated SDP
  */
-void ff_sdp_write_media(char *buff, int size, AVStream *st, int idx,
+void ff_sdp_write_media(char *buff, int size, const AVStream *st, int idx,
                         const char *dest_addr, const char *dest_type,
                         int port, int ttl, AVFormatContext *fmt);
 

libavformat/rtp.c

@@ -87,8 +87,8 @@ int ff_rtp_get_codec_info(AVCodecParameters *par, int payload_type)
     return -1;
 }
 
-int ff_rtp_get_payload_type(AVFormatContext *fmt,
-                            AVCodecParameters *par, int idx)
+int ff_rtp_get_payload_type(const AVFormatContext *fmt,
+                            const AVCodecParameters *par, int idx)
 {
     int i;
     const AVOutputFormat *ofmt = fmt ? fmt->oformat : NULL;

libavformat/rtp.h

@@ -38,8 +38,8 @@
  * @param idx   The stream index
  * @return The payload type (the 'PT' field in the RTP header).
  */
-int ff_rtp_get_payload_type(AVFormatContext *fmt, AVCodecParameters *par,
-                            int idx);
+int ff_rtp_get_payload_type(const AVFormatContext *fmt,
+                            const AVCodecParameters *par, int idx);
 
 /**
  * Initialize a codec context based on the payload type.

libavformat/sdp.c

@@ -151,7 +151,7 @@ static int sdp_get_address(char *dest_addr, int size, int *ttl, const char *url)
 }
 
 #define MAX_PSET_SIZE 1024
-static char *extradata2psets(AVFormatContext *s, AVCodecParameters *par)
+static char *extradata2psets(AVFormatContext *s, const AVCodecParameters *par)
 {
     char *psets, *p;
     const uint8_t *r;
@@ -222,7 +222,7 @@ static char *extradata2psets(AVFormatContext *s, AVCodecParameters *par)
     return psets;
 }
 
-static char *extradata2psets_hevc(AVCodecParameters *par)
+static char *extradata2psets_hevc(const AVCodecParameters *par)
 {
     char *psets;
     uint8_t *extradata = par->extradata;
@@ -323,7 +323,7 @@ err:
     return NULL;
 }
 
-static char *extradata2config(AVFormatContext *s, AVCodecParameters *par)
+static char *extradata2config(AVFormatContext *s, const AVCodecParameters *par)
 {
     char *config;
 
@@ -343,7 +343,7 @@ static char *extradata2config(AVFormatContext *s, AVCodecParameters *par)
     return config;
 }
 
-static char *xiph_extradata2config(AVFormatContext *s, AVCodecParameters *par)
+static char *xiph_extradata2config(AVFormatContext *s, const AVCodecParameters *par)
 {
     uint8_t *config;
     char *encoded_config;
@@ -413,7 +413,7 @@ xiph_fail:
     return NULL;
 }
 
-static int latm_context2profilelevel(AVCodecParameters *par)
+static int latm_context2profilelevel(const AVCodecParameters *par)
 {
     /* MP4A-LATM
      * The RTP payload format specification is described in RFC 3016
@@ -442,7 +442,7 @@ static int latm_context2profilelevel(AVCodecParameters *par)
     return profile_level;
 }
 
-static char *latm_context2config(AVFormatContext *s, AVCodecParameters *par)
+static char *latm_context2config(AVFormatContext *s, const AVCodecParameters *par)
 {
     /* MP4A-LATM
      * The RTP payload format specification is described in RFC 3016
@@ -477,10 +477,11 @@ static char *latm_context2config(AVFormatContext *s, AVCodecParameters *par)
     return config;
 }
 
-static char *sdp_write_media_attributes(char *buff, int size, AVStream *st, int payload_type, AVFormatContext *fmt)
+static char *sdp_write_media_attributes(char *buff, int size, const AVStream *st,
+                                        int payload_type, AVFormatContext *fmt)
 {
     char *config = NULL;
-    AVCodecParameters *p = st->codecpar;
+    const AVCodecParameters *p = st->codecpar;
 
     switch (p->codec_id) {
         case AV_CODEC_ID_DIRAC:
@@ -762,11 +763,11 @@ static char *sdp_write_media_attributes(char *buff, int size, AVStream *st, int
     return buff;
 }
 
-void ff_sdp_write_media(char *buff, int size, AVStream *st, int idx,
+void ff_sdp_write_media(char *buff, int size, const AVStream *st, int idx,
                         const char *dest_addr, const char *dest_type,
                         int port, int ttl, AVFormatContext *fmt)
 {
-    AVCodecParameters *p = st->codecpar;
+    const AVCodecParameters *p = st->codecpar;
     const char *type;
     int payload_type;
 
@@ -863,7 +864,7 @@ int av_sdp_create(AVFormatContext *ac[], int n_files, char *buf, int size)
     return AVERROR(ENOSYS);
 }
 
-void ff_sdp_write_media(char *buff, int size, AVStream *st, int idx,
+void ff_sdp_write_media(char *buff, int size, const AVStream *st, int idx,
                         const char *dest_addr, const char *dest_type,
                         int port, int ttl, AVFormatContext *fmt)
 {