[FFmpeg-devel] [PATCH/RFC] subtitles: introduce ASS codec id and use it.

Clément Bœsch ubitux at gmail.com
Tue Apr 9 22:12:32 CEST 2013


Since it seems Google doesn't want to lend me a minion for the subtitles
work this summer, I'll have to take some responsibilities about it... :(

On Fri, Jan 04, 2013 at 11:51:45AM +0100, Nicolas George wrote:
[...]
> >   - lavf/mkv: adding the codec id ASS makes the demuxer output them by
> >     default without any "SSA-lines" reconstruction hack. The muxer is
> 
> Looks dangerous, from a compatibility point of view. What I had in mind was
> this:
> 
> * Print a warning whenever the old codec is used.
> 
> * In the transition period, use AVFormatContext.subtitle_codec_id to tell
>   the demuxer that new ASS is accepted.
> 

This looks like way too much pain to handle correctly: forcing codec id in
our apps in case of MKV can be not trivial to do, and even if we do it, it
seems not enough since the codec forcing seems to only affect the mapped
output streams (in the case of ffmpeg), and thus will warn N-1 times for a
mkv file with N ASS streams for instance.

I think I'll keep the ASS packets by default with MKV: the introduction of
AV_CODEC_ID_ASS will be lavf minor bumped, and making old and new code
compatible with both SSA and ASS should be easy and trivial for an app.

> >     updated to take by default ASS packets (and still supports the old
> >     SSA packets).
> > 
> > [1]: http://www.matroska.org/technical/specs/subtitles/ssa.html
> > ---
> > Patch is still in RFC mode since there are a few FATE failures because of CLRF
> > not present in the ASS header... sometimes. I need to investigate a bit more,
> > and also run a few more tests since some stuff is left untested. But right now,
> > I need some sleep. Comments welcome :)
> 
> Did you try to transcode a file with simultaneous events? My guess is it
> will fail with the infamous non monotonic timestamps error. We need to find
> a way of making the check lax (AVFMT_TS_NONSTRICT) for ASS streams.
> Hopefully without adding "if (codec_id == ASS)" in the middle of lavf's
> framework files.
> 

It seems OK so far, as long as you don't try to force stupid settings
(such as forcing transcoding from ssa to ass codecs).

[...]
> > +#if CONFIG_ASS_DECODER
> > +static int ass_decode_frame(AVCodecContext *avctx, void *data, int *got_sub_ptr,
> > +                            AVPacket *avpkt)
> >  {
> > -    ff_ass_split_free(avctx->priv_data);
> > -    avctx->priv_data = NULL;
> > -    return 0;
> > +    AVSubtitle *sub = data;
> > +    const char *ptr = avpkt->data;
> 
> > +    const int ts_start    = av_rescale_q(avpkt->pts,      avctx->time_base, (AVRational){1,100});
> > +    const int ts_duration = av_rescale_q(avpkt->duration, avctx->time_base, (AVRational){1,100});
> 
> static const AVRational ass_time_base = { 1, 100 };
> and use it everywhere?
> 

Changed.

> Also: check for overflows?
> 

Well… we'll need to fix all the other decoders if so. The patch looks big
enough to me now.

> > +
> > +    if (avpkt->size <= 0)
> > +        return avpkt->size;
> > +
> 
> > +    /* ReadOrder */
> > +    while (*ptr && *ptr != ',')
> > +        ptr++;
> > +    if (*ptr == ',')
> > +        ptr++;
> 
> strchr? And fail if it is not present?
> 
> > +
> > +    /* Layer or Marked */
> > +    //layer = ptr;
> > +    while (*ptr && *ptr != ',')
> > +        ptr++;
> 
> Factor that out?
> 
> > +
> > +    if (*ptr == ',')
> 
> Error report?
> 

I've move and reworked that code to honor these last 3 comments.

[...]
> > +            if (i > 0) {
> > +                av_log(avctx, AV_LOG_WARNING, "ASS encoder supports only one "
> > +                       "ASS rectangle field. The following event will not be "
> > +                       "encoded: \"%s\"\n", ass);
> > +                continue;
> > +            }
> 
> Please fail: discarding users' data in the middle of an encoding with just a
> warning is evil.
> 

OK

> > +
> > +            ass += 10; // skip "Dialogue: "
> > +            /* parse Layer field. If it's a Marked field, the content
> > +             * will be "Marked=N" instead of the layer num, so we will
> > +             * have layer=0, which is fine. */
> > +            layer = strtol(ass, &p, 10);
> > +            if (*p) p += strcspn(p, ",") + 1; // skip layer or marked
> > +            if (*p) p += strcspn(p, ",") + 1; // skip start timestamp
> > +            if (*p) p += strcspn(p, ",") + 1; // skip end timestamp
> 
> > +            snprintf(ass_line, sizeof(ass_line), "%d,%ld,%s", ++s->id, layer, p);
> 
> Missing overflow check.
> 

Erm, is it really important?

[...]
> > diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> > index 30f153c..1276859 100644
> > --- a/libavcodec/avcodec.h
> > +++ b/libavcodec/avcodec.h
> > @@ -470,6 +470,7 @@ enum AVCodecID {
> >      AV_CODEC_ID_MPL2       = MKBETAG('M','P','L','2'),
> >      AV_CODEC_ID_VPLAYER    = MKBETAG('V','P','l','r'),
> >      AV_CODEC_ID_PJS        = MKBETAG('P','h','J','S'),
> > +    AV_CODEC_ID_ASS        = MKBETAG('A','S','S',' '),  ///< ASS such as muxed in Matroska (no timings info for instance)
> 
> "such as" does not sound right here.
> 

Reworded.

-- 
Clément B.
-------------- next part --------------
From 0489657f511565089ca03927ed3196a871327628 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20B=C5=93sch?= <ubitux at gmail.com>
Date: Thu, 3 Jan 2013 03:06:43 +0100
Subject: [PATCH] subtitles: introduce ASS codec id and use it.

Currently, we have a AV_CODEC_ID_SSA, which matches the way the ASS/SSA
markup is muxed in a standalone .ass/.ssa file. This means the AVPacket
data starts with a "Dialogue:" string, followed by a timing information
(start and end of the event as string) and a trailing CRLF after each
line. One packet can contain several lines. We'll refer to this layout
as "SSA" or "SSA lines".

In matroska, this markup is not stored as such: it has no "Dialogue:"
prefix, it contains a ReadOrder field, the timing information is not in
the payload, and it doesn't contain the trailing CRLF. See [1] for more
info. We'll refer to this layout as "ASS".

Since we have only one common codec for both formats, the matroska
demuxer is constructing an AVPacket following the "SSA lines" format.
This causes several problems, so it was decided to change this into
clean ASS packets.

Some insight about what is changed or unchanged in this commit:

  CODECS
  ------

  - the decoding process still writes "SSA lines" markup inside the ass
    fields of the subtitles rectangles (sub->rects[n]->ass), which is
    still the current common way of representing decoded subtitles
    markup. It is meant to change later.

  - new ASS codec id: AV_CODEC_ID_ASS (which is different from the
    legacy AV_CODEC_ID_SSA)

  - lavc/assdec: the "ass" decoder is renamed into "ssa" (instead of
    "ass") for consistency with the codec id and allows to add a real
    ass decoder. This ass decoder receives clean ASS lines (so it starts
    with a ReadOrder, is followed by the Layer, etc). We make sure this
    is decoded properly in a new ass-line rectangle of the decoded
    subtitles (the ssa decoder OTOH is doing a simple straightforward
    copy). Using the packet timing instead of data string makes sure the
    ass-line now contains the appropriate timing.

  - lavc/assenc: just like the ass decoder, the "ssa" encoder is renamed
    into "ssa" (instead of "ass") for consistency with the codec id, and
    allows to add a real "ass" encoder.

    One important thing about this encoder is that it only supports one
    ass rectangle: we could have put several dialogue events in the
    AVPacket (separated by a \0 for instance) but this would have cause
    trouble for the muxer which needs not only the start time, but also
    the duration: typically, you have merged events with the same start
    time (stored in the AVPacket->pts) but a different duration. At the
    moment, only the matroska do the merge with the SSA-line codec.

    We will need to make sure all the decoders in the future can't add
    more than one rectangle (and only one Dialogue line in it
    obviously).

  FORMATS
  -------

  - lavf/assenc: the .ass/.ssa muxer can take both SSA and ASS packets.
    In the case of ASS packets as input, it adds the timing based on the
    AVPacket pts and duration, and mux it with "Dialogue:", trailing
    CRLF, etc.

  - lavf/assdec: unchanged; it currently still only outputs SSA-lines
    packets.

  - lavf/mkv: adding the codec id ASS makes the demuxer outputs them by
    default without any "SSA-lines" reconstruction hack. The muxer is
    updated to take by default ASS packets (and still supports the old
    SSA packets). All the SSA hacks in Matroska code will be dropped at
    next bump.

[1]: http://www.matroska.org/technical/specs/subtitles/ssa.html
---
 libavcodec/Makefile       |  2 ++
 libavcodec/allcodecs.c    |  1 +
 libavcodec/ass.c          | 24 ++++++++++++++++---
 libavcodec/ass.h          |  4 +++-
 libavcodec/assdec.c       | 52 +++++++++++++++++++++++++++++++++++------
 libavcodec/assenc.c       | 59 ++++++++++++++++++++++++++++++++++++++++++++---
 libavcodec/avcodec.h      |  1 +
 libavcodec/codec_desc.c   |  8 ++++++-
 libavformat/assenc.c      | 33 ++++++++++++++++++++++++--
 libavformat/matroska.c    |  6 +++++
 libavformat/matroskadec.c | 14 ++++++++++-
 libavformat/matroskaenc.c |  4 +++-
 libavformat/version.h     |  3 +++
 13 files changed, 192 insertions(+), 19 deletions(-)

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index fcb006a..abe2860 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -111,6 +111,8 @@ OBJS-$(CONFIG_AMV_ENCODER)             += mjpegenc.o mjpeg.o           \
 OBJS-$(CONFIG_ANM_DECODER)             += anm.o
 OBJS-$(CONFIG_ANSI_DECODER)            += ansi.o cga_data.o
 OBJS-$(CONFIG_APE_DECODER)             += apedec.o
+OBJS-$(CONFIG_SSA_DECODER)             += assdec.o ass.o ass_split.o
+OBJS-$(CONFIG_SSA_ENCODER)             += assenc.o ass.o
 OBJS-$(CONFIG_ASS_DECODER)             += assdec.o ass.o ass_split.o
 OBJS-$(CONFIG_ASS_ENCODER)             += assenc.o ass.o
 OBJS-$(CONFIG_ASV1_DECODER)            += asvdec.o asv.o mpeg12data.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index 4ff63ef..c6cb620 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -449,6 +449,7 @@ void avcodec_register_all(void)
     REGISTER_DECODER(VIMA,              vima);
 
     /* subtitles */
+    REGISTER_ENCDEC (SSA,               ssa);
     REGISTER_ENCDEC (ASS,               ass);
     REGISTER_ENCDEC (DVBSUB,            dvbsub);
     REGISTER_ENCDEC (DVDSUB,            dvdsub);
diff --git a/libavcodec/ass.c b/libavcodec/ass.c
index 87c73a5..b263c63 100644
--- a/libavcodec/ass.c
+++ b/libavcodec/ass.c
@@ -85,17 +85,35 @@ int ff_ass_add_rect(AVSubtitle *sub, const char *dialog,
     AVSubtitleRect **rects;
 
     av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
-    if (!raw) {
-        av_bprintf(&buf, "Dialogue: 0,");
+    if (!raw || raw == 2) {
+        long int layer = 0;
+
+        if (raw == 2) {
+            /* skip ReadOrder */
+            dialog = strchr(dialog, ',');
+            if (!dialog)
+                return AVERROR_INVALIDDATA;
+            dialog++;
+
+            /* extract Layer or Marked */
+            layer = strtol(dialog, (char**)&dialog, 10);
+            if (*dialog != ',')
+                return AVERROR_INVALIDDATA;
+            dialog++;
+        }
+        av_bprintf(&buf, "Dialogue: %ld,", layer);
         insert_ts(&buf, ts_start);
         insert_ts(&buf, duration == -1 ? -1 : ts_start + duration);
-        av_bprintf(&buf, "Default,");
+        if (raw != 2)
+            av_bprintf(&buf, "Default,");
     }
 
     dlen = strcspn(dialog, "\n");
     dlen += dialog[dlen] == '\n';
 
     av_bprintf(&buf, "%.*s", dlen, dialog);
+    if (raw == 2)
+        av_bprintf(&buf, "\r\n");
     if (!av_bprint_is_complete(&buf))
         return AVERROR(ENOMEM);
 
diff --git a/libavcodec/ass.h b/libavcodec/ass.h
index e9339e4..ef99b58 100644
--- a/libavcodec/ass.h
+++ b/libavcodec/ass.h
@@ -76,7 +76,9 @@ int ff_ass_subtitle_header_default(AVCodecContext *avctx);
  * @param ts_start start timestamp for this dialog (in 1/100 second unit)
  * @param duration duration for this dialog (in 1/100 second unit), can be -1
  *                 to last until the end of the presentation
- * @param raw when set to 1, it indicates that dialog contains a whole ASS
+ * @param raw when set to 2, it indicates that dialog contains an ASS
+ *                           dialog line as muxed in Matroska
+ *            when set to 1, it indicates that dialog contains a whole SSA
  *                           dialog line which should be copied as is.
  *            when set to 0, it indicates that dialog contains only the Text
  *                           part of the ASS dialog line, the rest of the line
diff --git a/libavcodec/assdec.c b/libavcodec/assdec.c
index d790656..11dbde0 100644
--- a/libavcodec/assdec.c
+++ b/libavcodec/assdec.c
@@ -41,7 +41,15 @@ static av_cold int ass_decode_init(AVCodecContext *avctx)
     return 0;
 }
 
-static int ass_decode_frame(AVCodecContext *avctx, void *data, int *got_sub_ptr,
+static int ass_decode_close(AVCodecContext *avctx)
+{
+    ff_ass_split_free(avctx->priv_data);
+    avctx->priv_data = NULL;
+    return 0;
+}
+
+#if CONFIG_SSA_DECODER
+static int ssa_decode_frame(AVCodecContext *avctx, void *data, int *got_sub_ptr,
                             AVPacket *avpkt)
 {
     const char *ptr = avpkt->data;
@@ -64,19 +72,49 @@ static int ass_decode_frame(AVCodecContext *avctx, void *data, int *got_sub_ptr,
     return avpkt->size;
 }
 
-static int ass_decode_close(AVCodecContext *avctx)
+AVCodec ff_ssa_decoder = {
+    .name         = "ssa",
+    .long_name    = NULL_IF_CONFIG_SMALL("SSA (SubStation Alpha) subtitle"),
+    .type         = AVMEDIA_TYPE_SUBTITLE,
+    .id           = AV_CODEC_ID_SSA,
+    .init         = ass_decode_init,
+    .decode       = ssa_decode_frame,
+    .close        = ass_decode_close,
+};
+#endif
+
+#if CONFIG_ASS_DECODER
+static int ass_decode_frame(AVCodecContext *avctx, void *data, int *got_sub_ptr,
+                            AVPacket *avpkt)
 {
-    ff_ass_split_free(avctx->priv_data);
-    avctx->priv_data = NULL;
-    return 0;
+    int ret;
+    AVSubtitle *sub = data;
+    const char *ptr = avpkt->data;
+    static const AVRational ass_tb = {1, 100};
+    const int ts_start    = av_rescale_q(avpkt->pts,      avctx->time_base, ass_tb);
+    const int ts_duration = av_rescale_q(avpkt->duration, avctx->time_base, ass_tb);
+
+    if (avpkt->size <= 0)
+        return avpkt->size;
+
+    ret = ff_ass_add_rect(sub, ptr, ts_start, ts_duration, 2);
+    if (ret < 0) {
+        if (ret == AVERROR_INVALIDDATA)
+            av_log(avctx, AV_LOG_ERROR, "Invalid ASS packet\n");
+        return ret;
+    }
+
+    *got_sub_ptr = avpkt->size > 0;
+    return avpkt->size;
 }
 
 AVCodec ff_ass_decoder = {
     .name         = "ass",
-    .long_name    = NULL_IF_CONFIG_SMALL("SSA (SubStation Alpha) subtitle"),
+    .long_name    = NULL_IF_CONFIG_SMALL("ASS (Advanced SubStation Alpha) subtitle"),
     .type         = AVMEDIA_TYPE_SUBTITLE,
-    .id           = AV_CODEC_ID_SSA,
+    .id           = AV_CODEC_ID_ASS,
     .init         = ass_decode_init,
     .decode       = ass_decode_frame,
     .close        = ass_decode_close,
 };
+#endif
diff --git a/libavcodec/assenc.c b/libavcodec/assenc.c
index 50b89c0..7b8a540 100644
--- a/libavcodec/assenc.c
+++ b/libavcodec/assenc.c
@@ -22,10 +22,16 @@
 #include <string.h>
 
 #include "avcodec.h"
+#include "ass_split.h"
+#include "ass.h"
 #include "libavutil/avstring.h"
 #include "libavutil/internal.h"
 #include "libavutil/mem.h"
 
+typedef struct {
+    int id; ///< current event id, ReadOrder field
+} ASSEncodeContext;
+
 static av_cold int ass_encode_init(AVCodecContext *avctx)
 {
     avctx->extradata = av_malloc(avctx->subtitle_header_size + 1);
@@ -41,15 +47,47 @@ static int ass_encode_frame(AVCodecContext *avctx,
                             unsigned char *buf, int bufsize,
                             const AVSubtitle *sub)
 {
+    ASSEncodeContext *s = avctx->priv_data;
     int i, len, total_len = 0;
 
     for (i=0; i<sub->num_rects; i++) {
+        char ass_line[2048];
+        const char *ass = sub->rects[i]->ass;
+
         if (sub->rects[i]->type != SUBTITLE_ASS) {
             av_log(avctx, AV_LOG_ERROR, "Only SUBTITLE_ASS type supported.\n");
             return -1;
         }
 
-        len = av_strlcpy(buf+total_len, sub->rects[i]->ass, bufsize-total_len);
+        if (strncmp(ass, "Dialogue: ", 10)) {
+            av_log(avctx, AV_LOG_ERROR, "AVSubtitle rectangle ass \"%s\""
+                   " does not look like a SSA markup\n", ass);
+            return AVERROR_INVALIDDATA;
+        }
+
+        if (avctx->codec->id == AV_CODEC_ID_ASS) {
+            long int layer;
+            char *p;
+
+            if (i > 0) {
+                av_log(avctx, AV_LOG_ERROR, "ASS encoder supports only one "
+                       "ASS rectangle field.\n");
+                return AVERROR_INVALIDDATA;
+            }
+
+            ass += 10; // skip "Dialogue: "
+            /* parse Layer field. If it's a Marked field, the content
+             * will be "Marked=N" instead of the layer num, so we will
+             * have layer=0, which is fine. */
+            layer = strtol(ass, &p, 10);
+            if (*p) p += strcspn(p, ",") + 1; // skip layer or marked
+            if (*p) p += strcspn(p, ",") + 1; // skip start timestamp
+            if (*p) p += strcspn(p, ",") + 1; // skip end timestamp
+            snprintf(ass_line, sizeof(ass_line), "%d,%ld,%s", ++s->id, layer, p);
+            ass_line[strcspn(ass_line, "\r\n")] = 0;
+            ass = ass_line;
+        }
+        len = av_strlcpy(buf+total_len, ass, bufsize-total_len);
 
         if (len > bufsize-total_len-1) {
             av_log(avctx, AV_LOG_ERROR, "Buffer too small for ASS event.\n");
@@ -62,11 +100,26 @@ static int ass_encode_frame(AVCodecContext *avctx,
     return total_len;
 }
 
-AVCodec ff_ass_encoder = {
-    .name         = "ass",
+#if CONFIG_SSA_ENCODER
+AVCodec ff_ssa_encoder = {
+    .name         = "ssa",
     .long_name    = NULL_IF_CONFIG_SMALL("SSA (SubStation Alpha) subtitle"),
     .type         = AVMEDIA_TYPE_SUBTITLE,
     .id           = AV_CODEC_ID_SSA,
     .init         = ass_encode_init,
     .encode_sub   = ass_encode_frame,
+    .priv_data_size = sizeof(ASSEncodeContext),
+};
+#endif
+
+#if CONFIG_ASS_ENCODER
+AVCodec ff_ass_encoder = {
+    .name         = "ass",
+    .long_name    = NULL_IF_CONFIG_SMALL("ASS (Advanced SubStation Alpha) subtitle"),
+    .type         = AVMEDIA_TYPE_SUBTITLE,
+    .id           = AV_CODEC_ID_ASS,
+    .init         = ass_encode_init,
+    .encode_sub   = ass_encode_frame,
+    .priv_data_size = sizeof(ASSEncodeContext),
 };
+#endif
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 4f68fad..8568e9a 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -474,6 +474,7 @@ enum AVCodecID {
     AV_CODEC_ID_MPL2       = MKBETAG('M','P','L','2'),
     AV_CODEC_ID_VPLAYER    = MKBETAG('V','P','l','r'),
     AV_CODEC_ID_PJS        = MKBETAG('P','h','J','S'),
+    AV_CODEC_ID_ASS        = MKBETAG('A','S','S',' '),  ///< ASS as defined in Matroska (no timings info for instance)
 
     /* other specific kind of codecs (generally used for attachments) */
     AV_CODEC_ID_FIRST_UNKNOWN = 0x18000,           ///< A dummy ID pointing at the start of various fake codecs.
diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
index 2b3eed7..c8a5d11 100644
--- a/libavcodec/codec_desc.c
+++ b/libavcodec/codec_desc.c
@@ -2403,10 +2403,16 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .props     = AV_CODEC_PROP_BITMAP_SUB,
     },
     {
+        .id        = AV_CODEC_ID_ASS,
+        .type      = AVMEDIA_TYPE_SUBTITLE,
+        .name      = "ass",
+        .long_name = NULL_IF_CONFIG_SMALL("ASS (Advanced SSA) subtitle"),
+    },
+    {
         .id        = AV_CODEC_ID_SSA,
         .type      = AVMEDIA_TYPE_SUBTITLE,
         .name      = "ssa",
-        .long_name = NULL_IF_CONFIG_SMALL("SSA (SubStation Alpha) / ASS (Advanced SSA) subtitle"),
+        .long_name = NULL_IF_CONFIG_SMALL("SSA (SubStation Alpha) subtitle"),
     },
     {
         .id        = AV_CODEC_ID_MOV_TEXT,
diff --git a/libavformat/assenc.c b/libavformat/assenc.c
index bda507d..1b6e164 100644
--- a/libavformat/assenc.c
+++ b/libavformat/assenc.c
@@ -20,9 +20,11 @@
  */
 
 #include "avformat.h"
+#include "internal.h"
 
 typedef struct ASSContext{
     unsigned int extra_index;
+    int write_ts; // 0: ssa (timing in payload), 1: ass (matroska like)
 }ASSContext;
 
 static int write_header(AVFormatContext *s)
@@ -31,10 +33,13 @@ static int write_header(AVFormatContext *s)
     AVCodecContext *avctx= s->streams[0]->codec;
     uint8_t *last= NULL;
 
-    if(s->nb_streams != 1 || avctx->codec_id != AV_CODEC_ID_SSA){
+    if (s->nb_streams != 1 || (avctx->codec_id != AV_CODEC_ID_SSA &&
+                               avctx->codec_id != AV_CODEC_ID_ASS)) {
         av_log(s, AV_LOG_ERROR, "Exactly one ASS/SSA stream is needed.\n");
         return -1;
     }
+    ass->write_ts = avctx->codec_id == AV_CODEC_ID_ASS;
+    avpriv_set_pts_info(s->streams[0], 64, 1, 100);
 
     while(ass->extra_index < avctx->extradata_size){
         uint8_t *p  = avctx->extradata + ass->extra_index;
@@ -57,7 +62,31 @@ static int write_header(AVFormatContext *s)
 
 static int write_packet(AVFormatContext *s, AVPacket *pkt)
 {
-    avio_write(s->pb, pkt->data, pkt->size);
+    ASSContext *ass = s->priv_data;
+
+    if (ass->write_ts) {
+        long int layer;
+        char *p;
+        int64_t start = pkt->pts;
+        int64_t end   = start + pkt->duration;
+        int hh1, mm1, ss1, ms1;
+        int hh2, mm2, ss2, ms2;
+
+        p = pkt->data + strcspn(pkt->data, ",") + 1; // skip ReadOrder
+        layer = strtol(p, &p, 10);
+        if (*p == ',')
+            p++;
+        hh1 = (int)(start / 360000);    mm1 = (int)(start / 6000) % 60;
+        hh2 = (int)(end   / 360000);    mm2 = (int)(end   / 6000) % 60;
+        ss1 = (int)(start / 100) % 60;  ms1 = (int)(start % 100);
+        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);
+    } else {
+        avio_write(s->pb, pkt->data, pkt->size);
+    }
 
     avio_flush(s->pb);
 
diff --git a/libavformat/matroska.c b/libavformat/matroska.c
index 09eecf2..24b3303 100644
--- a/libavformat/matroska.c
+++ b/libavformat/matroska.c
@@ -61,10 +61,16 @@ const CodecTags ff_mkv_codec_tags[]={
     {"S_TEXT/UTF8"      , AV_CODEC_ID_TEXT},
     {"S_TEXT/UTF8"      , AV_CODEC_ID_SRT},
     {"S_TEXT/ASCII"     , AV_CODEC_ID_TEXT},
+    {"S_TEXT/ASS"       , AV_CODEC_ID_ASS},
+    {"S_TEXT/SSA"       , AV_CODEC_ID_ASS},
+    {"S_ASS"            , AV_CODEC_ID_ASS},
+    {"S_SSA"            , AV_CODEC_ID_ASS},
+#if FF_API_ASS_SSA
     {"S_TEXT/ASS"       , AV_CODEC_ID_SSA},
     {"S_TEXT/SSA"       , AV_CODEC_ID_SSA},
     {"S_ASS"            , AV_CODEC_ID_SSA},
     {"S_SSA"            , AV_CODEC_ID_SSA},
+#endif
     {"S_VOBSUB"         , AV_CODEC_ID_DVD_SUBTITLE},
     {"S_DVBSUB"         , AV_CODEC_ID_DVB_SUBTITLE},
     {"S_HDMV/PGS"       , AV_CODEC_ID_HDMV_PGS_SUBTITLE},
diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index ad0401a..c103dce 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -1213,6 +1213,7 @@ static int matroska_decode_buffer(uint8_t** buf, int* buf_size,
     return result;
 }
 
+#if FF_API_ASS_SSA
 static void matroska_fix_ass_packet(MatroskaDemuxContext *matroska,
                                     AVPacket *pkt, uint64_t display_duration)
 {
@@ -1259,6 +1260,7 @@ static int matroska_merge_packets(AVPacket *out, AVPacket *in)
     av_free(in);
     return 0;
 }
+#endif
 
 static void matroska_convert_tag(AVFormatContext *s, EbmlList *list,
                                  AVDictionary **metadata, char *prefix)
@@ -1859,7 +1861,12 @@ static int matroska_read_header(AVFormatContext *s)
             st->need_parsing = AVSTREAM_PARSE_HEADERS;
         } else if (track->type == MATROSKA_TRACK_TYPE_SUBTITLE) {
             st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
-            if (st->codec->codec_id == AV_CODEC_ID_SSA)
+#if FF_API_ASS_SSA
+            if (st->codec->codec_id == AV_CODEC_ID_SSA ||
+                st->codec->codec_id == AV_CODEC_ID_ASS)
+#else
+            if (st->codec->codec_id == AV_CODEC_ID_ASS)
+#endif
                 matroska->contains_ssa = 1;
         }
     }
@@ -2221,6 +2228,7 @@ static int matroska_parse_frame(MatroskaDemuxContext *matroska,
         pkt->duration = lace_duration;
     }
 
+#if FF_API_ASS_SSA
     if (st->codec->codec_id == AV_CODEC_ID_SSA)
         matroska_fix_ass_packet(matroska, pkt, lace_duration);
 
@@ -2234,6 +2242,10 @@ static int matroska_parse_frame(MatroskaDemuxContext *matroska,
         dynarray_add(&matroska->packets,&matroska->num_packets,pkt);
         matroska->prev_pkt = pkt;
     }
+#else
+    dynarray_add(&matroska->packets, &matroska->num_packets, pkt);
+    matroska->prev_pkt = pkt;
+#endif
 
     return 0;
 }
diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index a151eef..7dd6dd9 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -1236,8 +1236,10 @@ static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
 
     if (codec->codec_type != AVMEDIA_TYPE_SUBTITLE) {
         mkv_write_block(s, pb, MATROSKA_ID_SIMPLEBLOCK, pkt, keyframe << 7);
+#if FF_API_ASS_SSA
     } else if (codec->codec_id == AV_CODEC_ID_SSA) {
         duration = mkv_write_ass_blocks(s, pb, pkt);
+#endif
     } else if (codec->codec_id == AV_CODEC_ID_SRT) {
         duration = mkv_write_srt_blocks(s, pb, pkt);
     } else {
@@ -1418,7 +1420,7 @@ AVOutputFormat ff_matroska_muxer = {
          ff_codec_bmp_tags, ff_codec_wav_tags,
          additional_audio_tags, additional_video_tags, 0
     },
-    .subtitle_codec    = AV_CODEC_ID_SSA,
+    .subtitle_codec    = AV_CODEC_ID_ASS,
     .query_codec       = mkv_query_codec,
 };
 #endif
diff --git a/libavformat/version.h b/libavformat/version.h
index 17447c0..7087eba 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -73,6 +73,9 @@
 #ifndef FF_API_READ_PACKET
 #define FF_API_READ_PACKET             (LIBAVFORMAT_VERSION_MAJOR < 56)
 #endif
+#ifndef FF_API_ASS_SSA
+#define FF_API_ASS_SSA                 (LIBAVFORMAT_VERSION_MAJOR < 56)
+#endif
 #ifndef FF_API_R_FRAME_RATE
 #define FF_API_R_FRAME_RATE            1
 #endif
-- 
1.8.2.1

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