rtp: add module capabilities for RTP payload type parsers

modules/access/rtp/rtp.c

@@ -151,6 +151,40 @@ static const struct vlc_rtp_pt_owner_operations vlc_rtp_pt_owner_ops = {
     vlc_rtp_es_request, vlc_rtp_mux_request,
 };
 
+int vlc_rtp_pt_instantiate(vlc_object_t *obj, struct vlc_rtp_pt *restrict pt,
+                           const struct vlc_sdp_pt *restrict desc)
+{
+    char modname[32];
+    int ret = VLC_ENOTSUP;
+
+    if (strchr(desc->name, ',') != NULL)
+        /* Comma has special meaning in vlc_module_match(), forbid it */
+        return VLC_EINVAL;
+    if ((size_t)snprintf(modname, sizeof (modname), "%s/%s",
+                         desc->media->type, desc->name) >= sizeof (modname))
+        return VLC_ENOTSUP; /* Outlandish media type with long name */
+
+    module_t **mods;
+    ssize_t n = vlc_module_match("rtp parser", modname, true, &mods, NULL);
+
+    for (ssize_t i = 0; i < n; i++) {
+        vlc_rtp_parser_cb cb = vlc_module_map(vlc_object_logger(obj), mods[i]);
+        if (cb == NULL)
+            continue;
+
+        ret = cb(obj, pt, desc);
+        if (ret == VLC_SUCCESS) {
+            msg_Dbg(obj, "- module \"%s\"", module_get_name(mods[i], true));
+            assert(pt->ops != NULL);
+            ret = 0;
+            break;
+        }
+    }
+
+    free(mods);
+    return ret;
+}
+
 /**
  * Extracts port number from "[host]:port" or "host:port" strings,
  * and remove brackets from the host name.

modules/access/rtp/rtp.h

@@ -244,6 +244,30 @@ static inline void vlc_rtp_es_send(struct vlc_rtp_es *es, block_t *block)
  */
 extern struct vlc_rtp_es *const vlc_rtp_es_dummy;
 
+/**
+ * Callback prototype for RTP parser module.
+ *
+ * This is the callback prototype for any RTP payload format parser module.
+ *
+ * \param obj VLC object for logging and configuration
+ * \param pt RTP payload type
+ * \param desc[in] SDP payload format description and type mapping
+ *
+ * \return VLC_SUCCESS on success, an error code on failure.
+ */
+typedef int (*vlc_rtp_parser_cb)(vlc_object_t *obj, struct vlc_rtp_pt *pt,
+                                 const struct vlc_sdp_pt *desc);
+
+#define set_rtp_parser_callback(cb) \
+    { \
+        vlc_rtp_parser_cb cb__ = (cb); (void) cb__; \
+        set_callback(cb); \
+        set_capability("rtp parser", 0); \
+    }
+
+int vlc_rtp_pt_instantiate(vlc_object_t *obj, struct vlc_rtp_pt *restrict pt,
+                           const struct vlc_sdp_pt *restrict desc);
+
 void rtp_autodetect(vlc_object_t *, rtp_session_t *,
                     const struct vlc_rtp_pt_owner *restrict);
 

modules/access/rtp/rtpfmt.c

@@ -258,9 +258,12 @@ static struct vlc_rtp_pt *vlc_rtp_pt_create(vlc_object_t *obj,
     pt->owner = *owner;
     pt->frequency = desc->clock_rate;
     pt->channel_count = desc->channel_count;
+
+    if (vlc_rtp_pt_instantiate(obj, pt, desc) == 0)
+        return pt;
+
     pt->ops = NULL;
 
-    /* TODO: introduce module (capabilities) for payload types */
     if (strcmp(desc->media->type, "audio") == 0) {
         if (strcmp(desc->name, "PCMU") == 0)
             pt->ops = &rtp_audio_pcmu;