[FFmpeg-devel] [PATCH] libavformat/assenc: Add ignore_gaps option

[Rodger Combs]

This patch lets the user ignore ReadOrder when writing ASS subtitles, which is useful when e.g. streaming output.

From d3d4cb4da2382a1d762fa1e9bfafbaf3d18cf5c5 Mon Sep 17 00:00:00 2001
From: Rodger Combs <rodger.combs at gmail.com>
Date: Thu, 30 Oct 2014 04:33:17 -0500
Subject: [PATCH] libavformat/assenc: Add ignore_gaps option

---
 libavformat/assenc.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/libavformat/assenc.c b/libavformat/assenc.c
index 8225967..c7a1d1e 100644
--- a/libavformat/assenc.c
+++ b/libavformat/assenc.c
@@ -23,6 +23,8 @@
 #include "avformat.h"
 #include "internal.h"
 
+#include "libavutil/opt.h"
+
 typedef struct DialogueLine {
     int readorder;
     char *line;
@@ -30,12 +32,14 @@ typedef struct DialogueLine {
 } DialogueLine;
 
 typedef struct ASSContext{
+    const AVClass *class;
     int write_ts; // 0: ssa (timing in payload), 1: ass (matroska like)
     int expected_readorder;
     DialogueLine *dialogue_cache;
     DialogueLine *last_added_dialogue;
     int cache_size;
     int ssa_mode;
+    int ignore_gaps;
 }ASSContext;
 
 static int write_header(AVFormatContext *s)
@@ -178,7 +182,7 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
             return AVERROR(ENOMEM);
         }
         insert_dialogue(ass, dialogue);
-        purge_dialogues(s, 0);
+        purge_dialogues(s, ass->ignore_gaps);
     } else {
         avio_write(s->pb, pkt->data, pkt->size);
     }
@@ -192,6 +196,20 @@ static int write_trailer(AVFormatContext *s)
     return 0;
 }
 
+#define OFFSET(x) offsetof(ASSContext, x)
+#define E AV_OPT_FLAG_ENCODING_PARAM
+static const AVOption options[] = {
+    { "ignore_gaps", "write events immediately, even if they're out-of-order", OFFSET(ignore_gaps), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 1, E },
+    { NULL },
+};
+
+static const AVClass ass_class = {
+    .class_name = "ass muxer",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
 AVOutputFormat ff_ass_muxer = {
     .name           = "ass",
     .long_name      = NULL_IF_CONFIG_SMALL("SSA (SubStation Alpha) subtitle"),
@@ -203,4 +221,5 @@ AVOutputFormat ff_ass_muxer = {
     .write_packet   = write_packet,
     .write_trailer  = write_trailer,
     .flags          = AVFMT_GLOBALHEADER | AVFMT_NOTIMESTAMPS | AVFMT_TS_NONSTRICT,
+    .priv_class     = &ass_class,
 };
-- 
2.1.0.rc1.4.g764c739