[FFmpeg-devel] [PATCH 12/12] lavf/sccenc: write proper timecode, use proper stream timebase and split lines properly

[Baptiste Coudurier]

---
 libavformat/sccenc.c | 90 ++++++++++++++++++++++++++------------------
 1 file changed, 54 insertions(+), 36 deletions(-)

diff --git a/libavformat/sccenc.c b/libavformat/sccenc.c
index f3cf3d599c..dd6a4b36d8 100644
--- a/libavformat/sccenc.c
+++ b/libavformat/sccenc.c
@@ -23,16 +23,22 @@
 #include "internal.h"
 #include "libavutil/log.h"
 #include "libavutil/intreadwrite.h"
+#include "libavutil/timecode.h"
+#include "libavutil/opt.h"
 
 typedef struct SCCContext {
-    int prev_h, prev_m, prev_s, prev_f;
+    AVClass *av_class;
+    int64_t expected_pts;
     int inside;
     int n;
+    AVTimecode tc;
+    char *timecode_start;
 } SCCContext;
 
 static int scc_write_header(AVFormatContext *avf)
 {
     SCCContext *scc = avf->priv_data;
+    AVStream *st = avf->streams[0];
 
     if (avf->nb_streams != 1 ||
         avf->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE) {
@@ -46,11 +52,19 @@ static int scc_write_header(AVFormatContext *avf)
                avcodec_get_name(avf->streams[0]->codecpar->codec_id));
         return AVERROR(EINVAL);
     }
-    avpriv_set_pts_info(avf->streams[0], 64, 1, 1000);
-    avio_printf(avf->pb, "Scenarist_SCC V1.0\n");
 
-    scc->prev_h = scc->prev_m = scc->prev_s = scc->prev_f = -1;
-    scc->inside = 0;
+    if (!(st->time_base.den == 30000 && st->time_base.num == 1001)) {
+        av_log(avf, AV_LOG_ERROR, "Unsupported frame rate: %d/%d\n",
+               st->time_base.den, st->time_base.num);
+        return AVERROR(EINVAL);
+    }
+
+    if (av_timecode_init_from_string(&scc->tc, (AVRational){30000, 1001}, scc->timecode_start, avf) < 0)
+        return -1;
+
+    avio_printf(avf->pb, "Scenarist_SCC V1.0");
+
+    scc->expected_pts = -2;
 
     return 0;
 }
@@ -59,58 +73,60 @@ static int scc_write_packet(AVFormatContext *avf, AVPacket *pkt)
 {
     SCCContext *scc = avf->priv_data;
     int64_t pts = pkt->pts;
-    int i, h, m, s, f;
+    char tcbuf[AV_TIMECODE_STR_SIZE];
+    int i;
 
     if (pts == AV_NOPTS_VALUE) {
-        av_log(avf, AV_LOG_WARNING,
-               "Insufficient timestamps.\n");
-        return 0;
+        av_log(avf, AV_LOG_WARNING, "Insufficient timestamps\n");
+        return -1;
     }
 
-    h = (int)(pts / (3600000));
-    m = (int)(pts / (60000)) % 60;
-    s = (int)(pts /  1000) % 60;
-    f = (int)(pts %  1000) / 33;
+    if (!av_timecode_make_string(&scc->tc, tcbuf, pts))
+        return -1;
 
-    for (i = 0; i < pkt->size; i+=3) {
-        if (pkt->data[i] == 0xfc && ((pkt->data[i + 1] != 0x80 || pkt->data[i + 2] != 0x80)))
-            break;
-    }
-    if (i >= pkt->size)
-        return 0;
-
-    if (!scc->inside && (scc->prev_h != h || scc->prev_m != m || scc->prev_s != s || scc->prev_f != f)) {
-        avio_printf(avf->pb, "\n%02d:%02d:%02d:%02d\t", h, m, s, f);
-        scc->inside = 1;
-    }
     for (i = 0; i < pkt->size; i+=3) {
         if (i + 3 > pkt->size)
             break;
 
         if (pkt->data[i] != 0xfc || (pkt->data[i + 1] == 0x80 && pkt->data[i + 2] == 0x80))
             continue;
-        if (!scc->inside) {
-            avio_printf(avf->pb, "\n%02d:%02d:%02d:%02d\t", h, m, s, f);
-            scc->inside = 1;
+
+        if (pts > scc->expected_pts+1 || AV_RB16(&pkt->data[i + 1]) == 0x942c) {
+            avio_printf(avf->pb, "\r\n\n%s\t", tcbuf);
+            scc->expected_pts = pts;
+            scc->n = 0;
         }
+
         if (scc->n > 0)
             avio_printf(avf->pb, " ");
+
         avio_printf(avf->pb, "%02x%02x", pkt->data[i + 1], pkt->data[i + 2]);
+        scc->expected_pts += 1;
         scc->n++;
     }
-    if (scc->inside && (scc->prev_h != h || scc->prev_m != m || scc->prev_s != s || scc->prev_f != f)) {
-        avio_printf(avf->pb, "\n");
-        scc->n = 0;
-        scc->inside = 0;
-    }
 
-    scc->prev_h = h;
-    scc->prev_m = m;
-    scc->prev_s = s;
-    scc->prev_f = f;
     return 0;
 }
 
+static int scc_write_trailer(AVFormatContext *avf)
+{
+    avio_printf(avf->pb, "\n\n");
+    return 0;
+}
+
+static const AVOption scc_options[] = {
+    { "timecode_start", "Set the SCC file initial timecode",
+      offsetof(SCCContext, timecode_start), AV_OPT_TYPE_STRING, {.str = "00:00:00;00"}, CHAR_MIN, CHAR_MAX, AV_OPT_FLAG_ENCODING_PARAM},
+    { NULL },
+};
+
+static const AVClass scc_muxer_class = {
+    .class_name     = "scc muxer",
+    .item_name      = av_default_item_name,
+    .option         = scc_options,
+    .version        = LIBAVUTIL_VERSION_INT,
+};
+
 AVOutputFormat ff_scc_muxer = {
     .name           = "scc",
     .long_name      = NULL_IF_CONFIG_SMALL("Scenarist Closed Captions"),
@@ -118,6 +134,8 @@ AVOutputFormat ff_scc_muxer = {
     .priv_data_size = sizeof(SCCContext),
     .write_header   = scc_write_header,
     .write_packet   = scc_write_packet,
+    .write_trailer  = scc_write_trailer,
     .flags          = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS | AVFMT_TS_NONSTRICT,
     .subtitle_codec = AV_CODEC_ID_EIA_608,
+    .priv_class     = &scc_muxer_class,
 };
-- 
2.17.0 (Apple Git-106)