[FFmpeg-devel] [PATCH] Add SUP/PGS subtitle demuxer

[Marcus Johnson]

Here's a PGS subtitle sample from Eac3to:
https://dl.dropboxusercontent.com/u/52358991/English.zip


On Sat, Aug 30, 2014 at 9:38 AM, wm4 <nfxjfg at googlemail.com> wrote:

> ---
> Reverse engineered by looking at Petri Hintukainen's muxer patch, and
> also the mkvmerge sources. Tested with files extracted by mkvextract
> only (does someone have better samples?). No idea if a parser would be
> required for correct remuxing, but at least for decoding with lavc it
> probably isn't be needed, going by how pgssubdec.c is structured.
>
> At least files produced by mkvextract have the DTS always set to 0.
> I don't know whether 0 means "invalid value", or whether DTS should
> just always be discarded. (Actually setting the 0 DTS breaks seeking.)
> ---
>  libavformat/Makefile     |  1 +
>  libavformat/allformats.c |  1 +
>  libavformat/supdec.c     | 92
> ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 94 insertions(+)
>  create mode 100644 libavformat/supdec.c
>
> diff --git a/libavformat/Makefile b/libavformat/Makefile
> index 3d124fb..b4965fe 100644
> --- a/libavformat/Makefile
> +++ b/libavformat/Makefile
> @@ -405,6 +405,7 @@ OBJS-$(CONFIG_SRT_MUXER)                 += srtenc.o
>  OBJS-$(CONFIG_STR_DEMUXER)               += psxstr.o
>  OBJS-$(CONFIG_SUBVIEWER1_DEMUXER)        += subviewer1dec.o subtitles.o
>  OBJS-$(CONFIG_SUBVIEWER_DEMUXER)         += subviewerdec.o subtitles.o
> +OBJS-$(CONFIG_SUP_DEMUXER)               += supdec.o
>  OBJS-$(CONFIG_SWF_DEMUXER)               += swfdec.o swf.o
>  OBJS-$(CONFIG_SWF_MUXER)                 += swfenc.o swf.o
>  OBJS-$(CONFIG_TAK_DEMUXER)               += takdec.o apetag.o img2.o
> rawdec.o
> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
> index 8f70c4b..e6c0e5f 100644
> --- a/libavformat/allformats.c
> +++ b/libavformat/allformats.c
> @@ -280,6 +280,7 @@ void av_register_all(void)
>      REGISTER_DEMUXER (STR,              str);
>      REGISTER_DEMUXER (SUBVIEWER1,       subviewer1);
>      REGISTER_DEMUXER (SUBVIEWER,        subviewer);
> +    REGISTER_DEMUXER (SUP,              sup);
>      REGISTER_MUXDEMUX(SWF,              swf);
>      REGISTER_DEMUXER (TAK,              tak);
>      REGISTER_MUXER   (TEE,              tee);
> diff --git a/libavformat/supdec.c b/libavformat/supdec.c
> new file mode 100644
> index 0000000..1938b06
> --- /dev/null
> +++ b/libavformat/supdec.c
> @@ -0,0 +1,92 @@
> +/*
> + * 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 "avformat.h"
> +#include "internal.h"
> +#include "libavutil/intreadwrite.h"
> +
> +#define SUP_PGS_MAGIC 0x5047 /* "PG", big endian */
> +
> +static int sup_read_header(AVFormatContext *s)
> +{
> +    AVStream *st = avformat_new_stream(s, NULL);
> +    if (!st)
> +        return AVERROR(ENOMEM);
> +    st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
> +    st->codec->codec_id = AV_CODEC_ID_HDMV_PGS_SUBTITLE;
> +    avpriv_set_pts_info(st, 32, 1, 90000);
> +
> +    return 0;
> +}
> +
> +static int sup_read_packet(struct AVFormatContext *s, AVPacket *pkt)
> +{
> +    char tmp[3];
> +    size_t len;
> +    int64_t pts, pos;
> +    int ret;
> +
> +    pos = avio_tell(s->pb);
> +
> +    if (avio_rb16(s->pb) != SUP_PGS_MAGIC)
> +        return avio_feof(s->pb) ? AVERROR_EOF : AVERROR_INVALIDDATA;
> +
> +    pts = avio_rb32(s->pb);
> +    avio_rb32(s->pb); /* discard DTS (usually 0, and useless) */
> +
> +    // The packet-size is stored as part of the packet.
> +    if ((ret = avio_read(s->pb, tmp, 3)) < 0)
> +        return ret;
> +
> +    len = AV_RB16(tmp + 1);
> +
> +    if ((ret = av_new_packet(pkt, len + 3)) < 0)
> +        return ret;
> +
> +    memcpy(pkt->data, tmp, 3);
> +
> +    if ((ret = avio_read(s->pb, pkt->data + 3, len)) < 0) {
> +        av_free_packet(pkt);
> +        return ret;
> +    }
> +
> +    pkt->stream_index = 0;
> +    pkt->flags |= AV_PKT_FLAG_KEY;
> +    pkt->pos = pos;
> +    pkt->pts = pts;
> +
> +    return 0;
> +}
> +
> +static int sup_probe(AVProbeData *p)
> +{
> +    if (p->buf_size < 2 || memcmp(p->buf, "PG", 2))
> +        return 0;
> +    return AVPROBE_SCORE_EXTENSION;
> +}
> +
> +AVInputFormat ff_sup_demuxer = {
> +    .name           = "sup",
> +    .long_name      = NULL_IF_CONFIG_SMALL("raw HDMV Presentation Graphic
> Stream subtitles"),
> +    .extensions     = "sup",
> +    .mime_type      = "application/x-pgs",
> +    .read_probe     = sup_probe,
> +    .read_header    = sup_read_header,
> +    .read_packet    = sup_read_packet,
> +    .flags          = AVFMT_GENERIC_INDEX,
> +};
> --
> 2.1.0.rc1
>
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