@@ -620,6 +620,25 @@ Disable subtitle recording.

 Deprecated, see -bsf

 @end table

+@section Advanced Subtitle options:

+

+@table @option

+

+@item -fix_sub_duration

+Fix subtitles durations. For each subtitle, wait for the next packet in the

+same stream and adjust the duration of the first to avoid overlap. This is

+necessary with some subtitles codecs, especially DVB subtitles, because the

+duration in the original packet is only a rough estimate and the end is

+actually marked by an empty subtitle frame. Failing to use this option when

+necessary can result in exaggerated durations or muxing failures due to

+non-monotonic timestamps.

+

+Note that this option will delay the output of all data until the next

+subtitle packet is decoded: it may increase memory consumption and latency a

+lot.

+

+@end table

+

 @section Audio/Video grab options

 @table @option

@@ -1649,6 +1649,7 @@ static int decode_video(InputStream *ist, AVPacket *pkt, int *got_output)

 static int transcode_subtitles(InputStream *ist, AVPacket *pkt, int *got_output)

 {

     AVSubtitle subtitle;

+    int64_t pts = pkt->pts;

     int i, ret = avcodec_decode_subtitle2(ist->st->codec,

                                           &subtitle, got_output, pkt);

     if (ret < 0 || !*got_output) {

@@ -1657,6 +1658,26 @@ static int transcode_subtitles(InputStream *ist, AVPacket *pkt, int *got_output)

         return ret;

     }

+    if (ist->fix_sub_duration) {

+        if (ist->prev_sub.got_output) {

+            int end = av_rescale_q(pts - ist->prev_sub.pts, ist->st->time_base,

+                                   (AVRational){ 1, 1000 });

+            if (end < ist->prev_sub.subtitle.end_display_time) {

+                av_log(ist->st->codec, AV_LOG_DEBUG,

+                       "Subtitle duration reduced from %d to %d\n",

+                       ist->prev_sub.subtitle.end_display_time, end);

+                ist->prev_sub.subtitle.end_display_time = end;

+            }

+        }

+        FFSWAP(int64_t,    pts,         ist->prev_sub.pts);

+        FFSWAP(int,        *got_output, ist->prev_sub.got_output);

+        FFSWAP(int,        ret,         ist->prev_sub.ret);

+        FFSWAP(AVSubtitle, subtitle,    ist->prev_sub.subtitle);

+    }

+

+    if (!*got_output || !subtitle.num_rects)

+        return ret;

+

     rate_emu_sleep(ist);

     sub2video_update(ist, &subtitle, pkt->pts);

@@ -1667,7 +1688,7 @@ static int transcode_subtitles(InputStream *ist, AVPacket *pkt, int *got_output)

         if (!check_output_constraints(ist, ost) || !ost->encoding_needed)

             continue;

-        do_subtitle_out(output_files[ost->file_index]->ctx, ost, ist, &subtitle, pkt->pts);

+        do_subtitle_out(output_files[ost->file_index]->ctx, ost, ist, &subtitle, pts);

     }

     avsubtitle_free(&subtitle);

@@ -158,6 +158,8 @@ typedef struct OptionsContext {

     int        nb_copy_initial_nonkeyframes;

     SpecifierOpt *filters;

     int        nb_filters;

+    SpecifierOpt *fix_sub_duration;

+    int        nb_fix_sub_duration;

 } OptionsContext;

 typedef struct InputFilter {

@@ -223,6 +225,14 @@ typedef struct InputStream {

     int      resample_channels;

     uint64_t resample_channel_layout;

+    int fix_sub_duration;

+    struct { /* previous decoded subtitle and related variables */

+        int64_t pts;

+        int got_output;

+        int ret;

+        AVSubtitle subtitle;

+    } prev_sub;

+

     struct sub2video {

         int64_t last_pts;

         AVFilterBufferRef *ref;

@@ -593,6 +593,7 @@ static void add_input_streams(OptionsContext *o, AVFormatContext *ic)

         case AVMEDIA_TYPE_SUBTITLE:

             if(!ist->dec)

                 ist->dec = avcodec_find_decoder(dec->codec_id);

+            MATCH_PER_STREAM_OPT(fix_sub_duration, i, ist->fix_sub_duration, ic, st);

             break;

         case AVMEDIA_TYPE_ATTACHMENT:

         case AVMEDIA_TYPE_UNKNOWN:

@@ -2276,6 +2277,7 @@ const OptionDef options[] = {

     { "sn", OPT_BOOL | OPT_SUBTITLE | OPT_OFFSET, {.off = OFFSET(subtitle_disable)}, "disable subtitle" },

     { "scodec", HAS_ARG | OPT_SUBTITLE | OPT_FUNC2, {(void*)opt_subtitle_codec}, "force subtitle codec ('copy' to copy stream)", "codec" },

     { "stag", HAS_ARG | OPT_EXPERT | OPT_SUBTITLE | OPT_FUNC2, {(void*)opt_old2new}, "force subtitle tag/fourcc", "fourcc/tag" },

+    { "fix_sub_duration", OPT_BOOL | OPT_EXPERT | OPT_SUBTITLE | OPT_SPEC, {.off = OFFSET(fix_sub_duration)}, "fix subtitles duration" },

     /* grab options */

     { "vc", HAS_ARG | OPT_EXPERT | OPT_VIDEO | OPT_GRAB, {(void*)opt_video_channel}, "deprecated, use -channel", "channel" },