[FFmpeg-devel] [PATCH] matroska read_seek: make max diff for last known subtitle configurable

[Rainer Hochecker]

From: Rainer Hochecker <fernetmenta at online.de>

Allow players to reduce the time read_seek sets the file pos before desired position.
Hard coded 30 seconds is a lot and takes several seconds when the source is on
a network share.


Signed-off-by: Rainer Hochecker <fernetmenta at online.de>
---
 libavformat/matroskadec.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index f79511e..eb2bc31 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -353,6 +353,9 @@ typedef struct MatroskaDemuxContext {
 
     /* WebM DASH Manifest live flag/ */
     int is_live;
+
+    /* set file pos up to 30 seconds before desired timestamp on seek */
+    int subtitle_seek_diff;
 } MatroskaDemuxContext;
 
 typedef struct MatroskaBlock {
@@ -3407,7 +3410,7 @@ static int matroska_read_seek(AVFormatContext *s, int stream_index,
             while (index_sub >= 0 &&
                   index_min > 0 &&
                   tracks[i].stream->index_entries[index_sub].pos < st->index_entries[index_min].pos &&
-                  st->index_entries[index].timestamp - tracks[i].stream->index_entries[index_sub].timestamp < 30000000000 / matroska->time_scale)
+                  st->index_entries[index].timestamp - tracks[i].stream->index_entries[index_sub].timestamp < matroska->subtitle_seek_diff * 1E9 / matroska->time_scale)
                 index_min--;
         }
     }
@@ -3813,9 +3816,17 @@ static int webm_dash_manifest_read_packet(AVFormatContext *s, AVPacket *pkt)
 #define OFFSET(x) offsetof(MatroskaDemuxContext, x)
 static const AVOption options[] = {
     { "live", "flag indicating that the input is a live file that only has the headers.", OFFSET(is_live), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, AV_OPT_FLAG_DECODING_PARAM },
+    { "subtitle_seek_diff", "max difference in seconds between desired seek pos and last known subtitle pos.", OFFSET(subtitle_seek_diff), AV_OPT_TYPE_INT, {.i64 = 30}, 0, 30, AV_OPT_FLAG_DECODING_PARAM },
     { NULL },
 };
 
+static const AVClass matroska_class = {
+    .class_name = "matroska,webm demuxer",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
 static const AVClass webm_dash_class = {
     .class_name = "WebM DASH Manifest demuxer",
     .item_name  = av_default_item_name,
@@ -3828,6 +3839,7 @@ AVInputFormat ff_matroska_demuxer = {
     .long_name      = NULL_IF_CONFIG_SMALL("Matroska / WebM"),
     .extensions     = "mkv,mk3d,mka,mks",
     .priv_data_size = sizeof(MatroskaDemuxContext),
+    .priv_class     = &matroska_class,
     .read_probe     = matroska_probe,
     .read_header    = matroska_read_header,
     .read_packet    = matroska_read_packet,
-- 
2.9.3