m3u8: Parse and use AVERAGE-BANDWIDTH attribute if available

The AVERAGE-BANDWIDTH attribute in the EXT-X-STREAM-INF tag represents
the average segment bit rate of the Variant Stream, while the BANDWIDTH
attribute represents the peak segment bit rate of the Variant Stream.
(https://tools.ietf.org/html/draft-pantos-http-live-streaming-23#section-4.3.4.2)
Using the average bit rate instead of the peak bit rate for variant switching
is more efficient and appropriate. Sometimes due to VBR encoding,
the BANDWIDTH may represent a value way above the average bit rate,
which could result to players not switching to that variant stream
 although network bandwidth is sufficiently available.

https://bugzilla.gnome.org/show_bug.cgi?id=790821

diff --git a/ext/hls/m3u8.c b/ext/hls/m3u8.c
index 1d210c3..594a963 100644 (file)
--- a/ext/hls/m3u8.c
+++ b/ext/hls/m3u8.c
@@ -1529,8 +1529,15 @@ gst_hls_master_playlist_new_from_data (gchar * data, const gchar * base_uri)
       data += stream->iframe ? 26 : 18;
       while (data && parse_attributes (&data, &a, &v)) {
         if (g_str_equal (a, "BANDWIDTH")) {
+          if (!stream->bandwidth) {
+            if (!int_from_string (v, NULL, &stream->bandwidth))
+              GST_WARNING ("Error while reading BANDWIDTH");
+          }
+        } else if (g_str_equal (a, "AVERAGE-BANDWIDTH")) {
+          GST_DEBUG
+              ("AVERAGE-BANDWIDTH attribute available. Using it as stream bandwidth");
           if (!int_from_string (v, NULL, &stream->bandwidth))
-            GST_WARNING ("Error while reading BANDWIDTH");
+            GST_WARNING ("Error while reading AVERAGE-BANDWIDTH");
         } else if (g_str_equal (a, "PROGRAM-ID")) {
           if (!int_from_string (v, NULL, &stream->program_id))
             GST_WARNING ("Error while reading PROGRAM-ID");