sub: add SDH subtitle filter

Add subtitle filter to remove additions for deaf or hard-of-hearing
(SDH). This is for English, but may in part work for others too.
This is an ASS filter and the intention is that it can always be
enabled as it by default do not remove parts that may be normal text.
Harder filtering can be enabled with an additional option.

Signed-off-by: wm4 <wm4@nowhere>

1 files changed, 21 insertions, 5 deletions

diff --git a/sub/sd_ass.c b/sub/sd_ass.c
index 2d16afd821..afe8fa6dd9 100644
--- a/sub/sd_ass.c
+++ b/sub/sd_ass.c
@@ -259,8 +259,15 @@ static void decode(struct sd *sd, struct demux_packet *packet)
             packet->duration = UNKNOWN_DURATION;
         }
         char **r = lavc_conv_decode(ctx->converter, packet);
-        for (int n = 0; r && r[n]; n++)
-            ass_process_data(track, r[n], strlen(r[n]));
+        for (int n = 0; r && r[n]; n++) {
+            char *ass_line = r[n];
+            if (sd->opts->sub_filter_SDH)
+                ass_line = filter_SDH(sd, track->event_format, 0, ass_line, 0);
+            if (ass_line)
+                ass_process_data(track, ass_line, strlen(ass_line));
+            if (sd->opts->sub_filter_SDH)
+                talloc_free(ass_line);
+        }
         if (ctx->duration_unknown) {
             for (int n = 0; n < track->n_events - 1; n++) {
                 if (track->events[n].Duration == UNKNOWN_DURATION * 1000) {
@@ -272,9 +279,18 @@ static void decode(struct sd *sd, struct demux_packet *packet)
     } else {
         // Note that for this packet format, libass has an internal mechanism
         // for discarding duplicate (already seen) packets.
-        ass_process_chunk(track, packet->buffer, packet->len,
-                          llrint(packet->pts * 1000),
-                          llrint(packet->duration * 1000));
+        char *ass_line = packet->buffer;
+        int ass_len = packet->len;
+        if (sd->opts->sub_filter_SDH) {
+            ass_line = filter_SDH(sd, track->event_format, 1, ass_line, ass_len);
+            ass_len = strlen(ass_line);
+        }
+        if (ass_line)
+            ass_process_chunk(track, ass_line, ass_len,
+                              llrint(packet->pts * 1000),
+                              llrint(packet->duration * 1000));
+        if (sd->opts->sub_filter_SDH)
+            talloc_free(ass_line);
     }
 }