avformat/assdec: output ASS packets

After this the order from the original file is stored through readorder
when doing ffmpeg -i input.ass -c copy output.mkv.

And now that the ASS muxer honors the ReadOrder, extracting the ass back
(without transcoding) restores the original order.

1 files changed, 28 insertions, 7 deletions

diff --git a/libavformat/assdec.c b/libavformat/assdec.c
index a5f792aee4..a434a4c65e 100644
--- a/libavformat/assdec.c
+++ b/libavformat/assdec.c
@@ -29,6 +29,7 @@
 
 typedef struct ASSContext {
     FFDemuxSubtitlesQueue q;
+    unsigned readorder;
 } ASSContext;
 
 static int ass_probe(AVProbeData *p)
@@ -52,18 +53,36 @@ static int ass_read_close(AVFormatContext *s)
     return 0;
 }
 
-static int read_ts(const uint8_t *p, int64_t *start, int *duration)
+static int read_dialogue(ASSContext *ass, AVBPrint *dst, const uint8_t *p,
+                         int64_t *start, int *duration)
 {
+    int pos;
     int64_t end;
     int hh1, mm1, ss1, ms1;
     int hh2, mm2, ss2, ms2;
 
-    if (sscanf(p, "%*[^,],%d:%d:%d%*c%d,%d:%d:%d%*c%d",
+    if (sscanf(p, "Dialogue: %*[^,],%d:%d:%d%*c%d,%d:%d:%d%*c%d,%n",
                &hh1, &mm1, &ss1, &ms1,
-               &hh2, &mm2, &ss2, &ms2) == 8) {
+               &hh2, &mm2, &ss2, &ms2, &pos) >= 8) {
+
+        /* This is not part of the sscanf itself in order to handle an actual
+         * number (which would be the Layer) or the form "Marked=N" (which is
+         * the old SSA field, now replaced by Layer, and will be lead to Layer
+         * being 0 here). */
+        const int layer = atoi(p + 10);
+
         end    = (hh2*3600LL + mm2*60LL + ss2) * 100LL + ms2;
         *start = (hh1*3600LL + mm1*60LL + ss1) * 100LL + ms1;
         *duration = end - *start;
+
+        av_bprint_clear(dst);
+        av_bprintf(dst, "%u,%d,%s", ass->readorder++, layer, p + pos);
+
+        /* right strip the buffer */
+        while (dst->len > 0 &&
+               dst->str[dst->len - 1] == '\r' ||
+               dst->str[dst->len - 1] == '\n')
+            dst->str[--dst->len] = 0;
         return 0;
     }
     return -1;
@@ -88,7 +107,7 @@ static int64_t get_line(AVBPrint *buf, FFTextReader *tr)
 static int ass_read_header(AVFormatContext *s)
 {
     ASSContext *ass = s->priv_data;
-    AVBPrint header, line;
+    AVBPrint header, line, rline;
     int header_remaining, res = 0;
     AVStream *st;
     FFTextReader tr;
@@ -99,12 +118,13 @@ static int ass_read_header(AVFormatContext *s)
         return AVERROR(ENOMEM);
     avpriv_set_pts_info(st, 64, 1, 100);
     st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
-    st->codec->codec_id   = AV_CODEC_ID_SSA;
+    st->codec->codec_id   = AV_CODEC_ID_ASS;
 
     header_remaining = INT_MAX;
 
     av_bprint_init(&header, 0, AV_BPRINT_SIZE_UNLIMITED);
     av_bprint_init(&line,   0, AV_BPRINT_SIZE_UNLIMITED);
+    av_bprint_init(&rline,  0, AV_BPRINT_SIZE_UNLIMITED);
 
     for (;;) {
         int64_t pos = get_line(&line, &tr);
@@ -125,9 +145,9 @@ static int ass_read_header(AVFormatContext *s)
             int duration = -1;
             AVPacket *sub;
 
-            if (read_ts(line.str, &ts_start, &duration) < 0)
+            if (read_dialogue(ass, &rline, line.str, &ts_start, &duration) < 0)
                 continue;
-            sub = ff_subtitles_queue_insert(&ass->q, line.str, line.len, 0);
+            sub = ff_subtitles_queue_insert(&ass->q, rline.str, rline.len, 0);
             if (!sub) {
                 res = AVERROR(ENOMEM);
                 goto end;
@@ -139,6 +159,7 @@ static int ass_read_header(AVFormatContext *s)
     }
 
     av_bprint_finalize(&line, NULL);
+    av_bprint_finalize(&rline, NULL);
 
     res = avpriv_bprint_to_extradata(st->codec, &header);
     if (res < 0)