Fix start_display_time/end_display_time to be relative to packet pts in xsub decoder.

Makes no difference for the sample AVI files since they all have no packet pts values.

Originally committed as revision 19646 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/xsubdec.c

@@ -30,7 +30,7 @@ static av_cold int decode_init(AVCodecContext *avctx) {
 static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
 static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
 
-static uint64_t parse_timecode(const uint8_t *buf) {
+static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
     int i;
     int64_t ms = 0;
     if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
@@ -40,7 +40,7 @@ static uint64_t parse_timecode(const uint8_t *buf) {
         if (c > 9) return AV_NOPTS_VALUE;
         ms = (ms + c) * tc_muls[i];
     }
-    return ms;
+    return ms - packet_time;
 }
 
 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
@@ -51,6 +51,7 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
     const uint8_t *buf_end = buf + buf_size;
     uint8_t *bitmap;
     int w, h, x, y, rlelen, i;
+    int64_t packet_time = 0;
     GetBitContext gb;
 
     memset(sub, 0, sizeof(*sub));
@@ -66,8 +67,10 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
         av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
         return -1;
     }
-    sub->start_display_time = parse_timecode(buf +  1);
-    sub->end_display_time   = parse_timecode(buf + 14);
+    if (avpkt->pts != AV_NOPTS_VALUE)
+        packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
+    sub->start_display_time = parse_timecode(buf +  1, packet_time);
+    sub->end_display_time   = parse_timecode(buf + 14, packet_time);
     buf += 27;
 
     // read header