[FFmpeg-devel] [PATCH] avcodec: add HDMV Text Subtitle decoder
Petri Hintukainen
phintuka at gmail.com
Wed Feb 1 11:05:48 EET 2017
ti, 2017-01-31 kello 16:42 +0100, wm4 kirjoitti:
> On Tue, 31 Jan 2017 15:22:17 +0100
> Paul B Mahol <onemda at gmail.com> wrote:
>
> > Signed-off-by: Paul B Mahol <onemda at gmail.com>
> > ---
> > libavcodec/Makefile | 2 +
> > libavcodec/allcodecs.c | 2 +
> > libavcodec/textst_parser.c | 49 ++++++++++++++++++++
> > libavcodec/textstdec.c | 108
> > +++++++++++++++++++++++++++++++++++++++++++++
> > libavformat/utils.c | 1 +
> > 5 files changed, 162 insertions(+)
> > create mode 100644 libavcodec/textst_parser.c
> > create mode 100644 libavcodec/textstdec.c
> >
> > diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> > index 43a6add..edadb0f 100644
> > --- a/libavcodec/Makefile
> > +++ b/libavcodec/Makefile
> > @@ -539,6 +539,7 @@ OBJS-$(CONFIG_SVQ1_ENCODER) +=
> > svq1enc.o svq1.o h263data.o \
> > OBJS-$(CONFIG_SVQ3_DECODER) += svq3.o svq13.o
> > mpegutils.o h264data.o
> > OBJS-$(CONFIG_TEXT_DECODER) += textdec.o ass.o
> > OBJS-$(CONFIG_TEXT_ENCODER) += srtenc.o ass_split.o
> > +OBJS-$(CONFIG_TEXTST_DECODER) += textstdec.o ass.o
> > OBJS-$(CONFIG_TAK_DECODER) += takdec.o tak.o takdsp.o
> > OBJS-$(CONFIG_TARGA_DECODER) += targa.o
> > OBJS-$(CONFIG_TARGA_ENCODER) += targaenc.o rle.o
> > @@ -945,6 +946,7 @@ OBJS-$(CONFIG_RV30_PARSER) +=
> > rv34_parser.o
> > OBJS-$(CONFIG_RV40_PARSER) += rv34_parser.o
> > OBJS-$(CONFIG_SIPR_PARSER) += sipr_parser.o
> > OBJS-$(CONFIG_TAK_PARSER) += tak_parser.o tak.o
> > +OBJS-$(CONFIG_TEXTST_PARSER) += textst_parser.o
> > OBJS-$(CONFIG_VC1_PARSER) += vc1_parser.o vc1.o
> > vc1data.o \
> > simple_idct.o wmv2data.o
> > OBJS-$(CONFIG_VP3_PARSER) += vp3_parser.o
> > diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
> > index f92b2b7..9a90533 100644
> > --- a/libavcodec/allcodecs.c
> > +++ b/libavcodec/allcodecs.c
> > @@ -581,6 +581,7 @@ void avcodec_register_all(void)
> > REGISTER_DECODER(SUBVIEWER, subviewer);
> > REGISTER_DECODER(SUBVIEWER1, subviewer1);
> > REGISTER_ENCDEC (TEXT, text);
> > + REGISTER_DECODER(TEXTST, textst);
> > REGISTER_DECODER(VPLAYER, vplayer);
> > REGISTER_ENCDEC (WEBVTT, webvtt);
> > REGISTER_ENCDEC (XSUB, xsub);
> > @@ -704,6 +705,7 @@ void avcodec_register_all(void)
> > REGISTER_PARSER(RV40, rv40);
> > REGISTER_PARSER(SIPR, sipr);
> > REGISTER_PARSER(TAK, tak);
> > + REGISTER_PARSER(TEXTST, textst);
> > REGISTER_PARSER(VC1, vc1);
> > REGISTER_PARSER(VORBIS, vorbis);
> > REGISTER_PARSER(VP3, vp3);
> > diff --git a/libavcodec/textst_parser.c
> > b/libavcodec/textst_parser.c
> > new file mode 100644
> > index 0000000..5079a96
> > --- /dev/null
> > +++ b/libavcodec/textst_parser.c
> > @@ -0,0 +1,49 @@
> > +/*
> > + * This file is part of FFmpeg.
> > + *
> > + * FFmpeg is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU Lesser General Public
> > + * License as published by the Free Software Foundation; either
> > + * version 2.1 of the License, or (at your option) any later
> > version.
> > + *
> > + * FFmpeg is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > GNU
> > + * Lesser General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU Lesser General
> > Public
> > + * License along with FFmpeg; if not, write to the Free Software
> > + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> > 02110-1301 USA
> > + */
> > +
> > +/**
> > + * @file
> > + * HDMV TextST subtitle parser
> > + */
> > +
> > +#include "libavutil/intreadwrite.h"
> > +#include "parser.h"
> > +
> > +static int textst_parse(AVCodecParserContext *s1, AVCodecContext
> > *avctx,
> > + const uint8_t **poutbuf, int
> > *poutbuf_size,
> > + const uint8_t *buf, int buf_size)
> > +{
> > + if (buf_size > 13) {
> > + int64_t end;
> > +
> > + s1->pts = ((int64_t)(buf[3] & 1) << 32) |
> > AV_RB32(&buf[4]);
> > + end = ((int64_t)(buf[8] & 1) << 32) | AV_RB32(&buf[9]);
> > + s1->duration = (end - s1->pts);
> > + }
> > +
> > + /* always return the full packet. this parser isn't doing any
> > splitting or
> > + combining, only packet analysis */
> > + *poutbuf = buf;
> > + *poutbuf_size = buf_size;
> > + return buf_size;
> > +}
> > +
> > +AVCodecParser ff_textst_parser = {
> > + .codec_ids = { AV_CODEC_ID_HDMV_TEXT_SUBTITLE },
> > + .parser_parse = textst_parse,
> > +};
>
> Why does it need to be in a parser, instead of the demuxer? It seems
> like this codec exists only in .ts anyway, and the way PTS/duration
> is
> extracted seems very closely tied to the format.
I think a parser could be good idea, it could be useful when remuxing ?
In the original BluRay mpeg-ts files this codec uses PES private stream
2, so there are no timestamps in packets coming from mpeg-ts demuxer.
Parser could also store the first segment (style segment) in extradata.
I think matroska stores style segment in extradata (not 100% sure, I
don't have such files at hand). This kind of makes sense, it allows
starting playback from middle of the mkv file.
Maybe parser should not overwrite the timestamps if those are already
present ? I don't know if timestamps in subtitle segments are modified
when muxing to matroska.
> > diff --git a/libavcodec/textstdec.c b/libavcodec/textstdec.c
> > new file mode 100644
> > index 0000000..a259d2d
> > --- /dev/null
> > +++ b/libavcodec/textstdec.c
> > @@ -0,0 +1,108 @@
> > +/*
> > + * HDMV TextST decoder
> > + * Copyright (c) 2017 Paul B Mahol
> > + *
> > + * This file is part of FFmpeg.
> > + *
> > + * FFmpeg is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU Lesser General Public
> > + * License as published by the Free Software Foundation; either
> > + * version 2.1 of the License, or (at your option) any later
> > version.
> > + *
> > + * FFmpeg is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > GNU
> > + * Lesser General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU Lesser General
> > Public
> > + * License along with FFmpeg; if not, write to the Free Software
> > + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> > 02110-1301 USA
> > + */
> > +
> > +#include <string.h>
> > +
> > +#include "libavutil/bprint.h"
> > +#include "avcodec.h"
> > +#include "ass.h"
> > +#include "bytestream.h"
> > +
> > +static int textst_event_to_ass(AVBPrint *buf, const char *p, int
> > size)
> > +{
> > + GetByteContext gb;
> > + int i, count;
> > +
> > + bytestream2_init(&gb, p, size);
> > + count = bytestream2_get_byte(&gb);
> > +
> > + if (count > 127) {
> > + int size = bytestream2_get_be16(&gb);
> > + bytestream2_skip(&gb, size);
> > + }
> > + if (bytestream2_get_bytes_left(&gb) > 2) {
> > + count = bytestream2_get_byte(&gb);
> > +
> > + for (i = 0; i < count; i++) {
> > + int dlength;
> > +
> > + bytestream2_skip(&gb, 2);
> > + dlength = bytestream2_get_be16(&gb);
> > +
> > + while (dlength > 3) {
> > + int type, length;
> > + int code = bytestream2_get_byte(&gb);
> > +
> > + dlength--;
> > + if (code != 0x1b)
> > + continue;
> > +
> > + type = bytestream2_get_byte(&gb);
> > + length = bytestream2_get_byte(&gb);
> > + dlength -= (2 + length);
> > +
> > + switch (type) {
> > + case 1:
> > + av_bprint_append_data(buf, gb.buffer,
> > FFMIN(length, bytestream2_get_bytes_left(&gb)));
> > + bytestream2_skip(&gb, length);
> > + break;
> > + case 0x0a:
> > + av_bprintf(buf, "\n");
> > + default:
> > + bytestream2_skip(&gb, length);
> > + break;
> > + }
> > + }
> > + }
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int textst_decode_frame(AVCodecContext *avctx,
> > + void *data, int *got_sub_ptr,
> > AVPacket *avpkt)
> > +{
> > + FFASSDecoderContext *s = avctx->priv_data;
> > + const char *ptr = avpkt->data;
> > + AVSubtitle *sub = data;
> > + AVBPrint buf;
> > + int ret = 0;
> > +
> > + av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
> > + if (ptr && avpkt->size > 13 && !textst_event_to_ass(&buf, ptr
> > + 13, avpkt->size - 13))
> > + ret = ff_ass_add_rect(sub, buf.str, s->readorder++, 0,
> > NULL, NULL);
> > + av_bprint_finalize(&buf, NULL);
> > + if (ret < 0)
> > + return ret;
> > + *got_sub_ptr = sub->num_rects > 0;
> > + return avpkt->size;
> > +}
> > +
> > +AVCodec ff_textst_decoder = {
> > + .name = "textst",
> > + .long_name = NULL_IF_CONFIG_SMALL("HDMV TextST
> > subtitle"),
> > + .type = AVMEDIA_TYPE_SUBTITLE,
> > + .id = AV_CODEC_ID_HDMV_TEXT_SUBTITLE,
> > + .decode = textst_decode_frame,
> > + .init = ff_ass_subtitle_header_default,
> > + .flush = ff_ass_decoder_flush,
> > + .priv_data_size = sizeof(FFASSDecoderContext),
> > +};
> > diff --git a/libavformat/utils.c b/libavformat/utils.c
> > index 0711310..74f808f 100644
> > --- a/libavformat/utils.c
> > +++ b/libavformat/utils.c
> > @@ -1445,6 +1445,7 @@ static int parse_packet(AVFormatContext *s,
> > AVPacket *pkt, int stream_index)
> >
> > out_pkt.stream_index = st->index;
> > out_pkt.pts = st->parser->pts;
> > + out_pkt.duration = st->parser->duration;
> > out_pkt.dts = st->parser->dts;
> > out_pkt.pos = st->parser->pos;
> >
>
> This overwrites values written to out_pkt.duration above this code.
> Does it even pass FATE?
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