[FFmpeg-devel] [PATCH v3 1/1] avformat/mpegtsenc: Write necessary descriptors into PMT for arib_caption muxing

[zheng qian]

Changes since v2:
  Generate stream_identifier and data_component_id from profile

The recognization of ARIB STD-B24 caption has been introduced
in commit a03885b, which is used as closed caption in
Japanese / Brazilian Digital Television.

But arib_caption stream copy is not working correctly caused by
the missing of descriptors in PMT. ARIB caption data inside
remuxed mpegts stream could not be recognized as an arib_caption
subtitle track once again because of the missing of descriptors.

This patch writes stream_identifier_descriptor and
data_component_descriptor by generating stream_identifier and
data_component_id from ARIB profile.

arib_caption remuxing could be worked correctly through this patch.

Signed-off-by: zheng qian <xqq at xqq.im>
---
 libavformat/mpegtsenc.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c
index a357f3a6aa..f302af84ff 100644
--- a/libavformat/mpegtsenc.c
+++ b/libavformat/mpegtsenc.c
@@ -357,6 +357,7 @@ static int get_dvb_stream_type(AVFormatContext *s, AVStream *st)
         break;
     case AV_CODEC_ID_DVB_SUBTITLE:
     case AV_CODEC_ID_DVB_TELETEXT:
+    case AV_CODEC_ID_ARIB_CAPTION:
         stream_type = STREAM_TYPE_PRIVATE_DATA;
         break;
     case AV_CODEC_ID_SMPTE_KLV:
@@ -714,6 +715,34 @@ static int mpegts_write_pmt(AVFormatContext *s, MpegTSService *service)
                }
 
                *len_ptr = q - len_ptr - 1;
+            } else if (codec_id == AV_CODEC_ID_ARIB_CAPTION) {
+                uint8_t stream_identifier;
+                uint16_t data_component_id;
+
+                if (st->codecpar->profile == FF_PROFILE_ARIB_PROFILE_A) {
+                    // non-mobile captioning service ("profile A")
+                    stream_identifier = 0x30;
+                    data_component_id = 0x0008;
+                } else if (st->codecpar->profile == FF_PROFILE_ARIB_PROFILE_C) {
+                    // (1seg) captioning service ("profile C")
+                    stream_identifier = 0x87;
+                    data_component_id = 0x0012;
+                } else {
+                    break;
+                }
+
+                // stream_identifier_descriptor
+                *q++ = 0x52;  // descriptor_tag
+                *q++ = 1;     // descriptor_length
+                *q++ = stream_identifier;  // component_tag: stream_identifier
+
+                // data_component_descriptor, defined in ARIB STD-B10, part 2, 6.2.20
+                *q++ = 0xFD;  // descriptor_tag: ARIB data coding type descriptor
+                *q++ = 3;     // descriptor_length
+                put16(&q, data_component_id);  // data_component_id
+                // additional_arib_caption_info: defined in ARIB STD-B24, fascicle 1, Part 3, 9.6.1
+                // Use most commonly used value 0x3D: DMF(0x3), Reserved(0x3), Timing(0x1)
+                *q++ = 0x3D;
             }
         break;
         case AVMEDIA_TYPE_VIDEO:
-- 
2.29.2