On Sat, 10 Apr 2021, zheng qian wrote:
Changes since v1:
If desc_len < 3, break the switch statement instead of return
AVERROR_INVALIDDATA
to make it more robust.
For arib_caption, data_component_descriptor should contains at least 3 bytes:
data_component_id: uint16, additional_arib_caption_info: uint8.
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 whenever copying arib_caption into mpegts output, arib_caption inside the
outputted stream cannot be recgonized as a arib_caption subtitle track once
again,
which is caused by the missing of descriptors in the PMT table.
These patches are intended to fix broken stream copying of arib_caption
subtitle.
This patch extracts necessary fields into codecpar->extradata for future
remuxing,
which describe the stream_identifier, the profile and other additional
information.
Signed-off-by: zheng qian <x...@xqq.im>
---
libavformat/mpegts.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index 6e0d9d7496..fd7ea1f504 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -2107,6 +2107,9 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc,
AVStream *st, int stream_type
// STD-B24, fascicle 3, chapter 4 defines private_stream_1
// for captions
if (stream_type == STREAM_TYPE_PRIVATE_DATA) {
+ if (desc_len < 3)
+ break;
+
// This structure is defined in STD-B10, part 1, listing 5.4 and
// part 2, 6.2.20).
// Listing of data_component_ids is in STD-B10, part 2, Annex J.
@@ -2145,6 +2148,28 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc,
AVStream *st, int stream_type
st->codecpar->codec_id = AV_CODEC_ID_ARIB_CAPTION;
st->codecpar->profile = picked_profile;
st->internal->request_probe = 0;
+
+ // Store stream_identifier and payload of data_component_descriptor
+ // (data_component_id & additional_arib_caption_info) as extradata.
+ // data_component_descriptor is defined in ARIB STD-B10, part 2,
6.2.20
+ // These will be useful for remuxing arib_caption into mpegts
output.
+ if (!st->codecpar->extradata) {
+ st->codecpar->extradata = av_mallocz(4 +
AV_INPUT_BUFFER_PADDING_SIZE);
+ if (!st->codecpar->extradata)
+ return AVERROR(ENOMEM);
+
+ st->codecpar->extradata_size = 4;
+
+ // stream_identifier (component_tag of
stream_identifier_descriptor)
+ st->codecpar->extradata[0] = (uint8_t)(st->stream_identifier -
1);
Storing this in extradata seems redundant. AVStream->stream_identifier
already exists, and you should be able to use that for muxing as well.
Regards,
Marton
+
+ // payload of data_component_descriptor structure
+ // data_component_id
+ st->codecpar->extradata[1] = (uint8_t)((data_component_id & 0xF0)
>> 8);
+ st->codecpar->extradata[2] = (uint8_t)(data_component_id &
0x0F);
+ // additional_arib_caption_info, defined in ARIB STD-B24,
fascicle 1, Part 3, 9.6.1
+ st->codecpar->extradata[3] = get8(pp, desc_end);
+ }
}
break;
case 0xb0: /* DOVI video stream descriptor */
--
2.29.2
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