I have already tried to use st->stream_identifier directly in mpegtsenc.c
while handling arib_caption stream in mpegts_write_pmt() function.
But in mpegtsenc.c, st->stream_identifier always provides
an incorrect value of 0, which should be 0x30 for arib_caption A profile.
st->stream_identifier seems hasn't been copied correctly while remuxing into
another mpegts stream. So I manually copied it.
On Sun, Apr 11, 2021 at 7:41 PM Marton Balint <c...@passwd.hu> wrote:
>
>
>
> 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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