input: add offset during seek by time operation

Add an offset of `priv->i_start` during the seek by time operation to correctly account
for the start time of individual segmented tracks. Modify the initial value passed to
`input_SetTime()` to 0, as the start offset (`priv->i_start`) has already been considered.

These changes ensure accurate timing and seek behavior in media files containing segmented tracks,
such as those defined by CUE files, by aligning the seek position with the actual timing of individual
segments.

src/input/input.c

@@ -556,7 +556,7 @@ static int MainLoopTryRepeat( input_thread_t *p_input )
 
     /* Seek to start position */
     if( priv->i_start > 0 )
-        input_SetTime( p_input, priv->i_start, false );
+        input_SetTime( p_input, 0, false );
     else
         input_SetPosition( p_input, 0.0f, false );
 
@@ -926,7 +926,7 @@ static void SetStopStart( input_thread_t * p_input )
         msg_Dbg( p_input, "starting at time: %"PRId64"s",
                  SEC_FROM_VLC_TICK(priv->i_start) );
 
-        input_SetTime( p_input, priv->i_start, false );
+        input_SetTime( p_input, 0, false );
     }
     if( priv->i_stop > 0 && priv->i_stop <= priv->i_start )
     {
@@ -1985,15 +1985,15 @@ static bool Control( input_thread_t *p_input,
             /* Reset the decoders states and clock sync (before calling the demuxer */
             es_out_Control(&priv->p_es_out->out, ES_OUT_RESET_PCR);
 
-            i_ret = demux_SetTime( priv->master->p_demux, param.time.i_val,
+            i_ret = demux_SetTime( priv->master->p_demux, priv->i_start + param.time.i_val,
                                    !param.time.b_fast_seek );
             if( i_ret )
             {
                 vlc_tick_t i_length = InputSourceGetLength( priv->master, priv->p_item );
                 /* Emulate it with a SET_POS */
                 if( i_length > 0 )
                 {
-                    double f_pos = (double)param.time.i_val / (double)i_length;
+                    double f_pos = (double)(priv->i_start + param.time.i_val) / (double)i_length;
                     i_ret = demux_SetPosition( priv->master->p_demux, f_pos,
                                                !param.time.b_fast_seek );
                 }