[vlc-devel] [PATCH] HttpLive stream_filter: alternative version of ChooseSegment function

[Łukasz Korbel]

You are completely right. Here is version with existing start-time:


>From 75f06911df5735716c547c186267b0791069176c Mon Sep 17 00:00:00 2001
From: Lukasz Korbel <korbel85 at gmail.com>
Date: Mon, 12 Mar 2012 17:17:53 +0100
Subject: [PATCH] HLS: implementation of start-time option

User can specify how long, after playlist beginning, to start playback.
Accuracy depends on segments length.
---
 modules/stream_filter/httplive.c |   56 +++++++++++++++++--------------------
 1 files changed, 26 insertions(+), 30 deletions(-)

diff --git a/modules/stream_filter/httplive.c b/modules/stream_filter/httplive.c
index b4ed58d..666eef3 100644
--- a/modules/stream_filter/httplive.c
+++ b/modules/stream_filter/httplive.c
@@ -125,6 +125,8 @@ struct stream_sys_t
         int         stream;     /* current hls_stream  */
         int         segment;    /* current segment for playback */
     } playback;
+    /* Settings for playback */
+    int    i_start_time; /* seconds after playlist first segment*/

     /* Playlist */
     struct hls_playlist_s
@@ -430,43 +432,34 @@ static int ChooseSegment(stream_t *s, const int current)
     hls_stream_t *hls = hls_Get(p_sys->hls_stream, current);
     if (hls == NULL) return 0;

-    /* Choose a segment to start which is no closer than
-     * 3 times the target duration from the end of the playlist.
-     */
-    int wanted = 0;
-    int duration = 0;
-    int sequence = 0;
+    int index = 0;
     int count = vlc_array_count(hls->segments);
-    int i = p_sys->b_live ? count - 1 : 0;
+    segment_t *segment;

-    while((i >= 0) && (i < count))
+    /* Use start-time value to determine first segment */
+    if (p_sys->i_start_time > 0)
     {
-        segment_t *segment = segment_GetSegment(hls, i);
-        assert(segment);
-
-        if (segment->duration > hls->duration)
+        int duration = 0;
+        /* Must start no later than from last but two segment:
+        http://tools.ietf.org/html/draft-pantos-http-live-streaming-00#section-6.2.2
*/
+        while (index < count - 2)
         {
-            msg_Err(s, "EXTINF:%d duration is larger than
EXT-X-TARGETDURATION:%d",
-                    segment->duration, hls->duration);
-        }
-
-        duration += segment->duration;
-        if (duration >= 3 * hls->duration)
-        {
-            /* Start point found */
-            wanted = p_sys->b_live ? i : 0;
-            sequence = segment->sequence;
-            break;
+            segment = segment_GetSegment(hls, index);
+            duration += segment->duration;
+            if (duration >= p_sys->i_start_time)
+                break; /* segment found */
+            else
+                index++;
         }
-
-        if (p_sys->b_live)
-            i-- ;
-        else
-            i++;
     }
+    else
+        segment = segment_GetSegment(hls, index);
+
+    /* query for starting segment sequence number */
+    int sequence = segment->sequence;

-    msg_Info(s, "Choose segment %d/%d (sequence=%d)", wanted, count, sequence);
-    return wanted;
+    msg_Info(s, "Choose segment %d/%d (sequence=%d)", index+1, count,
sequence);
+    return index;
 }

 /* Parsing */
@@ -1908,6 +1901,9 @@ static int Open(vlc_object_t *p_this)
     qsort( p_sys->hls_stream->pp_elems, p_sys->hls_stream->i_count,
            sizeof( hls_stream_t* ), &hls_CompareStreams );

+    /* Read playlist settings from config, implicit cast to int */
+    p_sys->i_start_time = var_InheritFloat(s, "start-time");
+
     /* Choose first HLS stream to start with */
     int current = p_sys->playback.stream = 0;
     p_sys->playback.segment = p_sys->download.segment =
ChooseSegment(s, current);
-- 
1.7.5.4

Regards,
Łukasz
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