avcodec/mpeg12dec: parse A53 caption data embedded in SCTE-20 user data

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/mpeg12dec.c

@@ -2240,6 +2240,45 @@ static int mpeg_decode_a53_cc(AVCodecContext *avctx,
             avctx->properties |= FF_CODEC_PROPERTY_CLOSED_CAPTIONS;
         }
         return 1;
+    } else if (buf_size >= 2 &&
+               p[0] == 0x03 && (p[1]&0x7f) == 0x01) {
+        /* extract SCTE-20 CC data */
+        GetBitContext gb;
+        int cc_count = 0;
+        int i;
+
+        init_get_bits(&gb, p + 2, buf_size - 2);
+        cc_count = get_bits(&gb, 5);
+        if (cc_count > 0) {
+            av_freep(&s1->a53_caption);
+            s1->a53_caption_size = cc_count * 3;
+            s1->a53_caption      = av_mallocz(s1->a53_caption_size);
+            if (s1->a53_caption) {
+                uint8_t field, cc1, cc2;
+                uint8_t *cap = s1->a53_caption;
+                for (i = 0; i < cc_count && get_bits_left(&gb) >= 26; i++) {
+                    skip_bits(&gb, 2); // priority
+                    field = get_bits(&gb, 2);
+                    skip_bits(&gb, 5); // line_offset
+                    cc1 = get_bits(&gb, 8);
+                    cc2 = get_bits(&gb, 8);
+                    skip_bits(&gb, 1); // marker
+
+                    if (!field) { // forbidden
+                        cap[0] = cap[1] = cap[2] = 0x00;
+                    } else {
+                        field = (field == 2 ? 1 : 0);
+                        if (!s1->mpeg_enc_ctx.top_field_first) field = !field;
+                        cap[0] = 0x04 | field;
+                        cap[1] = ff_reverse[cc1];
+                        cap[2] = ff_reverse[cc2];
+                    }
+                    cap += 3;
+                }
+            }
+            avctx->properties |= FF_CODEC_PROPERTY_CLOSED_CAPTIONS;
+        }
+        return 1;
     } else if (buf_size >= 11 &&
                p[0] == 'C' && p[1] == 'C' && p[2] == 0x01 && p[3] == 0xf8) {
         /* extract DVD CC data

tests/fate/subtitles.mak

@@ -7,6 +7,9 @@ fate-sub-cc: CMD = fmtstdout ass -f lavfi -i "movie=$(TARGET_SAMPLES)/sub/Closed
 FATE_SUBTITLES_ASS-$(call ALLYES, AVDEVICE LAVFI_INDEV CCAPTION_DECODER MOVIE_FILTER MPEGTS_DEMUXER) += fate-sub-cc-realtime
 fate-sub-cc-realtime: CMD = fmtstdout ass -real_time 1 -f lavfi -i "movie=$(TARGET_SAMPLES)/sub/Closedcaption_rollup.m2v[out0+subcc]"
 
+FATE_SUBTITLES_ASS-$(call ALLYES, AVDEVICE LAVFI_INDEV CCAPTION_DECODER MOVIE_FILTER MPEGTS_DEMUXER) += fate-sub-cc-scte20
+fate-sub-cc-scte20: CMD = fmtstdout ass -f lavfi -i "movie=$(TARGET_SAMPLES)/sub/scte20.ts[out0+subcc]"
+
 FATE_SUBTITLES_ASS-$(call DEMDEC, ASS, ASS) += fate-sub-ass-to-ass-transcode
 fate-sub-ass-to-ass-transcode: CMD = fmtstdout ass -i $(TARGET_SAMPLES)/sub/1ededcbd7b.ass
 

tests/ref/fate/sub-cc-scte20

@@ -0,0 +1,15 @@
+[Script Info]
+; Script generated by FFmpeg/Lavc
+ScriptType: v4.00+
+PlayResX: 384
+PlayResY: 288
+
+[V4+ Styles]
+Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
+Style: Default,Monospace,16,&Hffffff,&Hffffff,&H0,&H0,0,0,0,0,100,100,0,0,3,1,0,2,10,10,10,0
+
+[Events]
+Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
+Dialogue: 0,0:00:00.00,0:00:01.44,Default,,0,0,0,,{\an7}{\pos(48,182)}BESIDES THE 
+Dialogue: 0,0:00:01.43,0:00:03.93,Default,,0,0,0,,{\an7}{\pos(38,166)}\hBESIDES THE \N{\an7}{\pos(38,197)}SPENDING AND THIS, IS THAT CAR 
+Dialogue: 0,0:00:03.94,0:00:06.31,Default,,0,0,0,,{\an7}{\pos(38,182)}SPENDING AND THIS, IS THAT CAR \N{\an7}{\pos(38,197)}MANUFACTURERS ARE ABOUT AS