[FFmpeg-devel] [PATCH] avformat/assenc: honor ReadOrder

[Clément Bœsch]

---
 libavformat/assenc.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 85 insertions(+), 4 deletions(-)

diff --git a/libavformat/assenc.c b/libavformat/assenc.c
index 9fb9f23..acc21b9 100644
--- a/libavformat/assenc.c
+++ b/libavformat/assenc.c
@@ -19,12 +19,22 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include "libavutil/avstring.h"
 #include "avformat.h"
 #include "internal.h"
 
+typedef struct DialogueLine {
+    int readorder;
+    char *line;
+    struct DialogueLine *prev, *next;
+} DialogueLine;
+
 typedef struct ASSContext{
     unsigned int extra_index;
     int write_ts; // 0: ssa (timing in payload), 1: ass (matroska like)
+    int expected_readorder;
+    DialogueLine *dialogue_cache;
+    int cache_size;
 }ASSContext;
 
 static int write_header(AVFormatContext *s)
@@ -60,19 +70,82 @@ static int write_header(AVFormatContext *s)
     return 0;
 }
 
+static void purge_dialogues(AVFormatContext *s, int force)
+{
+    int n = 0;
+    ASSContext *ass = s->priv_data;
+    DialogueLine *dialogue = ass->dialogue_cache;
+
+    while (dialogue && (dialogue->readorder == ass->expected_readorder || force)) {
+        DialogueLine *next = dialogue->next;
+        if (dialogue->readorder != ass->expected_readorder) {
+            av_log(s, AV_LOG_WARNING, "ReadOrder gap found between %d and %d\n",
+                   ass->expected_readorder, dialogue->readorder);
+            ass->expected_readorder = dialogue->readorder;
+        }
+        avio_printf(s->pb, "Dialogue: %s\r\n", dialogue->line);
+        av_free(dialogue->line);
+        av_free(dialogue);
+        if (next)
+            next->prev = NULL;
+        dialogue = ass->dialogue_cache = next;
+        ass->expected_readorder++;
+        n++;
+    }
+    ass->cache_size -= n;
+    if (n > 1)
+        av_log(s, AV_LOG_DEBUG, "wrote %d ASS lines, cached dialogues: %d, waiting for event id %d\n",
+               n, ass->cache_size, ass->expected_readorder);
+}
+
+static void insert_dialogue(ASSContext *ass, DialogueLine *dialogue)
+{
+    DialogueLine *cur, *next, *prev = NULL;
+
+    next = ass->dialogue_cache;
+    for (cur = next; cur; cur = cur->next) {
+        if (cur->readorder > dialogue->readorder)
+            break;
+        prev = cur;
+        next = cur->next;
+    }
+    if (prev) {
+        prev->next = dialogue;
+        dialogue->prev = prev;
+    } else {
+        dialogue->prev = ass->dialogue_cache;
+        ass->dialogue_cache = dialogue;
+    }
+    if (next) {
+        next->prev = dialogue;
+        dialogue->next = next;
+    }
+    ass->cache_size++;
+}
+
 static int write_packet(AVFormatContext *s, AVPacket *pkt)
 {
     ASSContext *ass = s->priv_data;
 
     if (ass->write_ts) {
         long int layer;
-        char *p;
+        char *p = pkt->data;
         int64_t start = pkt->pts;
         int64_t end   = start + pkt->duration;
         int hh1, mm1, ss1, ms1;
         int hh2, mm2, ss2, ms2;
+        DialogueLine *dialogue = av_mallocz(sizeof(*dialogue));
+
+        if (!dialogue)
+            return AVERROR(ENOMEM);
+
+        dialogue->readorder = strtol(p, &p, 10);
+        if (dialogue->readorder < ass->expected_readorder)
+            av_log(s, AV_LOG_WARNING, "Unexpected ReadOrder %d\n",
+                   dialogue->readorder);
+        if (*p == ',')
+            p++;
 
-        p = pkt->data + strcspn(pkt->data, ",") + 1; // skip ReadOrder
         layer = strtol(p, &p, 10);
         if (*p == ',')
             p++;
@@ -82,8 +155,15 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
         ss2 = (int)(end   / 100) % 60;  ms2 = (int)(end   % 100);
         if (hh1 > 9) hh1 = 9, mm1 = 59, ss1 = 59, ms1 = 99;
         if (hh2 > 9) hh2 = 9, mm2 = 59, ss2 = 59, ms2 = 99;
-        avio_printf(s->pb, "Dialogue: %ld,%d:%02d:%02d.%02d,%d:%02d:%02d.%02d,%s\r\n",
-                    layer, hh1, mm1, ss1, ms1, hh2, mm2, ss2, ms2, p);
+
+        dialogue->line = av_asprintf("%ld,%d:%02d:%02d.%02d,%d:%02d:%02d.%02d,%s",
+                                     layer, hh1, mm1, ss1, ms1, hh2, mm2, ss2, ms2, p);
+        if (!dialogue->line) {
+            av_free(dialogue);
+            return AVERROR(ENOMEM);
+        }
+        insert_dialogue(ass, dialogue);
+        purge_dialogues(s, 0);
     } else {
         avio_write(s->pb, pkt->data, pkt->size);
     }
@@ -96,6 +176,7 @@ static int write_trailer(AVFormatContext *s)
     ASSContext *ass = s->priv_data;
     AVCodecContext *avctx= s->streams[0]->codec;
 
+    purge_dialogues(s, 1);
     avio_write(s->pb, avctx->extradata      + ass->extra_index,
                       avctx->extradata_size - ass->extra_index);
 
-- 
2.1.0