avformat/dashenc: add descriptor which is useful to the scheme defined by...

avformat/dashenc: add descriptor which is useful to the scheme defined by ISO/IEC 23009-1:2014/Amd.2:2015.
Signed-off-by: leozhang <leozhang@qiyi.com>

doc/muxers.texi

@@ -275,6 +275,10 @@ of the adaptation sets and a,b,c,d and e are the indices of the mapped streams.
 To map all video (or audio) streams to an AdaptationSet, "v" (or "a") can be used as stream identifier instead of IDs.
 
 When no assignment is defined, this defaults to an AdaptationSet for each stream.
+
+Optional syntax is "id=x,descriptor=descriptor_string,streams=a,b,c id=y,streams=d,e" and so on, descriptor is useful to the scheme defined by ISO/IEC 23009-1:2014/Amd.2:2015.
+For example, -adaptation_sets "id=0,descriptor=<SupplementalProperty schemeIdUri=\"urn:mpeg:dash:srd:2014\" value=\"0,0,0,1,1,2,2\"/>,streams=v".
+Please note that descriptor string should be a self-closing xml tag.
 @item timeout @var{timeout}
 Set timeout for socket I/O operations. Applicable only for HTTP output.
 @item index_correction @var{index_correction}

libavformat/dashenc.c

@@ -68,6 +68,7 @@ typedef struct Segment {
 
 typedef struct AdaptationSet {
     char id[10];
+    char *descriptor;
     enum AVMediaType media_type;
     AVDictionary *metadata;
     AVRational min_frame_rate, max_frame_rate;
@@ -552,8 +553,10 @@ static void dash_free(AVFormatContext *s)
     int i, j;
 
     if (c->as) {
-        for (i = 0; i < c->nb_as; i++)
+        for (i = 0; i < c->nb_as; i++) {
             av_dict_free(&c->as[i].metadata);
+            av_freep(&c->as[i].descriptor);
+        }
         av_freep(&c->as);
         c->nb_as = 0;
     }
@@ -748,7 +751,8 @@ static int write_adaptation_set(AVFormatContext *s, AVIOContext *out, int as_ind
     role = av_dict_get(as->metadata, "role", NULL, 0);
     if (role)
         avio_printf(out, "\t\t\t<Role schemeIdUri=\"urn:mpeg:dash:role:2011\" value=\"%s\"/>\n", role->value);
-
+    if (as->descriptor)
+        avio_printf(out, "\t\t\t%s\n", as->descriptor);
     for (i = 0; i < s->nb_streams; i++) {
         OutputStream *os = &c->streams[i];
         char bandwidth_str[64] = {'\0'};
@@ -820,7 +824,7 @@ static int parse_adaptation_sets(AVFormatContext *s)
 {
     DASHContext *c = s->priv_data;
     const char *p = c->adaptation_sets;
-    enum { new_set, parse_id, parsing_streams } state;
+    enum { new_set, parse_id, parsing_streams, parse_descriptor } state;
     AdaptationSet *as;
     int i, n, ret;
 
@@ -837,6 +841,9 @@ static int parse_adaptation_sets(AVFormatContext *s)
     }
 
     // syntax id=0,streams=0,1,2 id=1,streams=3,4 and so on
+    // option id=0,descriptor=descriptor_str,streams=0,1,2 and so on
+    // descriptor is useful to the scheme defined by ISO/IEC 23009-1:2014/Amd.2:2015
+    // descriptor_str should be a self-closing xml tag.
     state = new_set;
     while (*p) {
         if (*p == ' ') {
@@ -854,7 +861,19 @@ static int parse_adaptation_sets(AVFormatContext *s)
             if (*p)
                 p++;
             state = parse_id;
-        } else if (state == parse_id && av_strstart(p, "streams=", &p)) {
+        } else if (state == parse_id && av_strstart(p, "descriptor=", &p)) {
+            n = strcspn(p, ">") + 1; //followed by one comma, so plus 1
+            if (n < strlen(p)) {
+                as->descriptor = av_strndup(p, n);
+            } else {
+                av_log(s, AV_LOG_ERROR, "Parse error, descriptor string should be a self-closing xml tag\n");
+                return AVERROR(EINVAL);
+            }
+            p += n;
+            if (*p)
+                p++;
+            state = parse_descriptor;
+        } else if ((state == parse_id || state == parse_descriptor) && av_strstart(p, "streams=", &p)) { //descriptor is optional
             state = parsing_streams;
         } else if (state == parsing_streams) {
             AdaptationSet *as = &c->as[c->nb_as - 1];