avformat/dashdec: Avoid multiple HTTP requests for initialization segment that is common among all representations

Reviewed-by: Steven Liu <lq@chinaffmpeg.org>
Signed-off-by: sanilraut <raut.sanil@gmail.com>

libavformat/dashdec.c

@@ -149,6 +149,11 @@ typedef struct DASHContext {
     char *allowed_extensions;
     AVDictionary *avio_opts;
     int max_url_size;
+
+    /* Flags for init section*/
+    int is_init_section_common_video;
+    int is_init_section_common_audio;
+
 } DASHContext;
 
 static int ishttp(char *url)
@@ -1862,6 +1867,45 @@ fail:
     return ret;
 }
 
+static int init_section_compare_video(DASHContext *c)
+{
+    int i = 0;
+    char *url = c->videos[0]->init_section->url;
+    int64_t url_offset = c->videos[0]->init_section->url_offset;
+    int64_t size = c->videos[0]->init_section->size;
+    for (i=0;i<c->n_videos;i++) {
+        if (av_strcasecmp(c->videos[i]->init_section->url,url) || c->videos[i]->init_section->url_offset != url_offset || c->videos[i]->init_section->size != size) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
+static int init_section_compare_audio(DASHContext *c)
+{
+    int i = 0;
+    char *url = c->audios[0]->init_section->url;
+    int64_t url_offset = c->audios[0]->init_section->url_offset;
+    int64_t size = c->audios[0]->init_section->size;
+    for (i=0;i<c->n_audios;i++) {
+        if (av_strcasecmp(c->audios[i]->init_section->url,url) || c->audios[i]->init_section->url_offset != url_offset || c->audios[i]->init_section->size != size) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
+static void copy_init_section(struct representation *rep_dest, struct representation *rep_src)
+{
+    memcpy(rep_dest->init_section, rep_src->init_section, sizeof(rep_src->init_section));
+    rep_dest->init_sec_buf = av_mallocz(rep_src->init_sec_buf_size);
+    memcpy(rep_dest->init_sec_buf, rep_src->init_sec_buf, rep_src->init_sec_data_len);
+    rep_dest->init_sec_buf_size = rep_src->init_sec_buf_size;
+    rep_dest->init_sec_data_len = rep_src->init_sec_data_len;
+    rep_dest->cur_timestamp = rep_src->cur_timestamp;
+}
+
+
 static int dash_read_header(AVFormatContext *s)
 {
     void *u = (s->flags & AVFMT_FLAG_CUSTOM_IO) ? NULL : s->pb;
@@ -1890,19 +1934,35 @@ static int dash_read_header(AVFormatContext *s)
         s->duration = (int64_t) c->media_presentation_duration * AV_TIME_BASE;
     }
 
+    if (c->n_videos) {
+        c->is_init_section_common_video = init_section_compare_video(c);
+    }
+
     /* Open the demuxer for video and audio components if available */
     for (i = 0; i < c->n_videos; i++) {
         struct representation *cur_video = c->videos[i];
+        if (i > 0 && c->is_init_section_common_video) {
+            copy_init_section(cur_video,c->videos[0]);
+        }
         ret = open_demux_for_component(s, cur_video);
+
         if (ret)
             goto fail;
         cur_video->stream_index = stream_index;
         ++stream_index;
     }
 
+    if (c->n_audios) {
+        c->is_init_section_common_audio = init_section_compare_audio(c);
+    }
+
     for (i = 0; i < c->n_audios; i++) {
         struct representation *cur_audio = c->audios[i];
+        if (i > 0 && c->is_init_section_common_audio) {
+            copy_init_section(cur_audio,c->audios[0]);
+        }
         ret = open_demux_for_component(s, cur_audio);
+
         if (ret)
             goto fail;
         cur_audio->stream_index = stream_index;