[FFmpeg-devel] [PATCH] lavc: add detection of forced subtitles

[Scott Theisen <scott.the.elm@gmail.com>]

This is from the following MythTV commits:
libavcodec: add support for detecting forced subtitle segments. https://github.com/MythTV/mythtv/commit/5099f1a5777966fba482b623e581c1eef5c8fc09
This adds forced subtitle segment detection to the PGS subtitle decoder and
copies the result to AVSubtitle.

Subtitles: Flag forced DVD subtitles. https://github.com/MythTV/mythtv/commit/78f71eecdbd53ba92af2ad639b32564c01f24563
---
 libavcodec/avcodec.h   | 1 +
 libavcodec/dvdsubdec.c | 4 +++-
 libavcodec/pgssubdec.c | 4 ++++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 7db5d1b1c5..b9aa9efb2f 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -2331,6 +2331,7 @@ typedef struct AVSubtitle {
     unsigned num_rects;
     AVSubtitleRect **rects;
     int64_t pts;    ///< Same as packet pts, in AV_TIME_BASE
+    int forced;
 } AVSubtitle;
 
 /**
diff --git a/libavcodec/dvdsubdec.c b/libavcodec/dvdsubdec.c
index a5da0d7b08..1504706d52 100644
--- a/libavcodec/dvdsubdec.c
+++ b/libavcodec/dvdsubdec.c
@@ -418,8 +418,10 @@ static int decode_dvd_subtitles(DVDSubContext *ctx, AVSubtitle *sub_header,
             break;
         cmd_pos = next_cmd_pos;
     }
-    if (sub_header->num_rects > 0)
+    if (sub_header->num_rects > 0) {
+        sub_header->forced = is_menu;
         return is_menu;
+    }
  fail:
     reset_rects(sub_header);
     return -1;
diff --git a/libavcodec/pgssubdec.c b/libavcodec/pgssubdec.c
index 5f76f12615..7c953263bb 100644
--- a/libavcodec/pgssubdec.c
+++ b/libavcodec/pgssubdec.c
@@ -62,6 +62,7 @@ typedef struct PGSSubPresentation {
     int id_number;
     int palette_id;
     int object_count;
+    int object_forced;
     PGSSubObjectRef objects[MAX_OBJECT_REFS];
     int64_t pts;
 } PGSSubPresentation;
@@ -466,6 +467,8 @@ static int parse_presentation_segment(AVCodecContext *avctx,
             object->crop_h = bytestream_get_be16(&buf);
         }
 
+        ctx->presentation.object_forced = (ctx->presentation.objects[i].composition_flag & 0x40) >> 6;
+
         ff_dlog(avctx, "Subtitle Placement x=%d, y=%d\n",
                 object->x, object->y);
 
@@ -505,6 +508,7 @@ static int display_end_segment(AVCodecContext *avctx, AVSubtitle *sub,
     memset(sub, 0, sizeof(*sub));
     sub->pts = pts;
     ctx->presentation.pts = AV_NOPTS_VALUE;
+    sub->forced = ctx->presentation.object_forced;
     sub->start_display_time = 0;
     // There is no explicit end time for PGS subtitles.  The end time
     // is defined by the start of the next sub which may contain no
-- 
2.34.1

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