rtpdec: Allow allocating and freeing the private data without explicit functions

This can reduce the amount of boilerplate in simple depacketizers.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/rtpdec.h

@@ -120,6 +120,7 @@ struct RTPDynamicProtocolHandler {
     int static_payload_id; /* 0 means no payload id is set. 0 is a valid
                             * payload ID (PCMU), too, but that format doesn't
                             * require any custom depacketization code. */
+    int priv_data_size;
 
     /** Initialize dynamic protocol handler, called after the full rtpmap line is parsed, may be null */
     int (*init)(AVFormatContext *s, int st_index, PayloadContext *priv_data);

libavformat/rtsp.c

@@ -190,6 +190,10 @@ static void init_rtp_handler(RTPDynamicProtocolHandler *handler,
         rtsp_st->dynamic_protocol_context = handler->alloc();
         if (!rtsp_st->dynamic_protocol_context)
             rtsp_st->dynamic_handler = NULL;
+    } else if (handler->priv_data_size) {
+        rtsp_st->dynamic_protocol_context = av_mallocz(handler->priv_data_size);
+        if (!rtsp_st->dynamic_protocol_context)
+            rtsp_st->dynamic_handler = NULL;
     }
 }
 
@@ -721,9 +725,13 @@ void ff_rtsp_close_streams(AVFormatContext *s)
     for (i = 0; i < rt->nb_rtsp_streams; i++) {
         rtsp_st = rt->rtsp_streams[i];
         if (rtsp_st) {
-            if (rtsp_st->dynamic_handler && rtsp_st->dynamic_protocol_context)
+            if (rtsp_st->dynamic_handler && rtsp_st->dynamic_protocol_context) {
+                if (rtsp_st->dynamic_handler->free)
                     rtsp_st->dynamic_handler->free(
                         rtsp_st->dynamic_protocol_context);
+                else
+                    av_free(rtsp_st->dynamic_protocol_context);
+            }
             for (j = 0; j < rtsp_st->nb_include_source_addrs; j++)
                 av_free(rtsp_st->include_source_addrs[j]);
             av_freep(&rtsp_st->include_source_addrs);