From 1aef780b6cd7743df7e21cfb7dc45ad5f99e0825 Mon Sep 17 00:00:00 2001
From: Tsukasa OMOTO <henry0312@gmail.com>
Date: Mon, 30 Jun 2014 02:44:32 +0900
Subject: options: support setting start time relative to start PTS

Signed-off-by: wm4 <wm4@nowhere>
---
 DOCS/man/options.rst |  9 ++++++---
 options/m_option.c   |  7 +++++--
 options/m_option.h   |  2 +-
 player/misc.c        | 11 ++++++++---
 4 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/DOCS/man/options.rst b/DOCS/man/options.rst
index eacb3fbde9..7dfc4bf884 100644
--- a/DOCS/man/options.rst
+++ b/DOCS/man/options.rst
@@ -2133,7 +2133,8 @@ OPTIONS
     Seek to given time position.
 
     The general format for absolute times is ``[[hh:]mm:]ss[.ms]``. If the time
-    is negated with ``-``, the seek is relative from the end of the file.
+    is given with a prefix of ``+`` or ``-``, the seek is relative from the start
+    or end of the file.
 
     ``pp%`` seeks to percent position pp (0-100).
 
@@ -2141,8 +2142,10 @@ OPTIONS
 
     .. admonition:: Examples
 
-        ``--start=56``
-            Seeks to 56 seconds.
+        ``--start=+56``, ``--start=+00:56``
+            Seeks to the start time + 56 seconds.
+        ``--start=-56``, ``--start=-00:56``
+            Seeks to the end time - 56 seconds.
         ``--start=01:10:00``
             Seeks to 1 hour 10 min.
         ``--start=50%``
diff --git a/options/m_option.c b/options/m_option.c
index 04b4783dc1..3baaaa6762 100644
--- a/options/m_option.c
+++ b/options/m_option.c
@@ -2181,10 +2181,13 @@ static int parse_rel_time(struct mp_log *log, const m_option_t *opt,
         }
     }
 
-    bool sign = bstr_eatstart0(&param, "-");
     double time;
     if (parse_timestring(param, &time, 0)) {
-        t.type = sign ? REL_TIME_NEGATIVE : REL_TIME_ABSOLUTE;
+        if (bstr_startswith0(param, "+") || bstr_startswith0(param, "-")) {
+            t.type = REL_TIME_RELATIVE;
+        } else {
+            t.type = REL_TIME_ABSOLUTE;
+        }
         t.pos = time;
         goto out;
     }
diff --git a/options/m_option.h b/options/m_option.h
index 02fcb9bfca..13afea22df 100644
--- a/options/m_option.h
+++ b/options/m_option.h
@@ -70,7 +70,7 @@ typedef void (*m_opt_print_fn)(struct mp_log *log);
 enum m_rel_time_type {
     REL_TIME_NONE,
     REL_TIME_ABSOLUTE,
-    REL_TIME_NEGATIVE,
+    REL_TIME_RELATIVE,
     REL_TIME_PERCENT,
     REL_TIME_CHAPTER,
 };
diff --git a/player/misc.c b/player/misc.c
index 6eae646242..6aa58863e8 100644
--- a/player/misc.c
+++ b/player/misc.c
@@ -53,12 +53,17 @@ double get_relative_time(struct MPContext *mpctx)
 double rel_time_to_abs(struct MPContext *mpctx, struct m_rel_time t)
 {
     double length = get_time_length(mpctx);
+    double start = get_start_time(mpctx);
     switch (t.type) {
     case REL_TIME_ABSOLUTE:
         return t.pos;
-    case REL_TIME_NEGATIVE:
-        if (length != 0)
-            return MPMAX(length - t.pos, 0.0);
+    case REL_TIME_RELATIVE:
+        if (t.pos >= 0) {
+            return start + t.pos;
+        } else {
+            if (length != 0)
+                return MPMAX(start + length + t.pos, 0.0);
+        }
         break;
     case REL_TIME_PERCENT:
         if (length != 0)
-- 
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