[FFmpeg-devel] [PATCH] DVB EPG decoder

[Aman Gupta]

On Sat, Sep 7, 2019 at 11:39 AM Marton Balint <cus at passwd.hu> wrote:

>
>
> On Wed, 4 Sep 2019, Anthony Delannoy wrote:
>
> > Hi
> >
> > I'm still interested to have those three commits merged (update in
> attachments).
>
> Ok, below are some more comments.
>
> >
> > But I'd like to see data decoder in the future to use more easily
> > EPG/NIT/BAT etc tables.
> > Will it be possible? With modifications if it needs to be?
>
> I don't see how, as it does not fit into the concept of the libav*
> libraries. I feel this belongs to a separate library.
>
> > From 335b0bf377c1e5cfc5207561adc9621b113759b0 Mon Sep 17 00:00:00 2001
> > From: Anthony Delannoy <anthony.2lannoy at gmail.com>
> > Date: Wed, 21 Aug 2019 11:46:56 +0200
> > Subject: [PATCH 3/3] lavf/mpegts: EPG extraction from mpegts
> >
> > ---
> >  libavformat/mpegts.c | 71 ++++++++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 69 insertions(+), 2 deletions(-)
> >
> > diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
> > index 0415ceea02..9bb6b6add8 100644
> > --- a/libavformat/mpegts.c
> > +++ b/libavformat/mpegts.c
> > @@ -168,6 +168,8 @@ struct MpegTSContext {
> >      /** filters for various streams specified by PMT + for the PAT and
> PMT */
> >      MpegTSFilter *pids[NB_PID_MAX];
> >      int current_pid;
> > +
> > +    AVStream *epg_stream;
> >  };
> >
> >  #define MPEGTS_OPTIONS \
> > @@ -2498,13 +2500,68 @@ static void pat_cb(MpegTSFilter *filter, const
> uint8_t *section, int section_len
> >      }
> >  }
> >
> > +static void eit_cb(MpegTSFilter *filter, const uint8_t *section, int
> section_len)
> > +{
> > +    MpegTSContext *ts = filter->u.section_filter.opaque;
> > +    const uint8_t *p, *p_end;
> > +    SectionHeader h1, *h = &h1;
> > +
> > +    /*
> > +     * Sometimes we receive EPG packets but SDT table do not have
> > +     * eit_pres_following or eit_sched turned on, so we open EPG
> > +     * stream directly here.
> > +     */
> > +    if (!ts->epg_stream) {
> > +        ts->epg_stream = avformat_new_stream(ts->stream, NULL);
> > +        if (!ts->epg_stream)
> > +            return;
> > +        ts->epg_stream->id = EIT_PID;
> > +        ts->epg_stream->codecpar->codec_type = AVMEDIA_TYPE_DATA;
> > +        ts->epg_stream->codecpar->codec_id = AV_CODEC_ID_EPG;
> > +    }
> > +
> > +    if (ts->epg_stream->discard == AVDISCARD_ALL)
> > +        return;
> > +
> > +    p_end = section + section_len - 4;
> > +    p     = section;
> > +
> > +    if (parse_section_header(h, &p, p_end) < 0)
> > +        return;
> > +    if (h->tid < EIT_TID || h->tid > OEITS_END_TID)
> > +        return;
> > +
> > +    av_log(ts->stream, AV_LOG_TRACE, "EIT: tid received = %.02x\n",
> h->tid);
> > +
> > +    /**
> > +     * Service_id 0xFFFF is reserved, it indicates that the current EIT
> table
> > +     * is scrambled.
> > +     */
> > +    if (h->id == 0xFFFF) {
> > +        av_log(ts->stream, AV_LOG_WARNING, "Scrambled EIT table
> received.\n");
> > +        return;
> > +    }
>
> In case of a scrambled EIT (which I have never seen myself in the wild)
> you'd
> print this at every packet. You should either remove the warning, or check
> if
> this is the first time (e.g. by checking if the EPG stream was just
> created).
>

I have a sample if anyone is interested. AFAIK it is only used by HD BBC
broadcasts in the UK.

https://tmm1.s3.amazonaws.com/dvb-eit/uk-eit-hd.ts

https://stackoverflow.com/questions/37765956/linux-dvb-v5-library-example-code-for-eit-grabbing#comment66609009_37765956


>
> > +
> > +    /**
> > +     * In case we receive an EPG packet before mpegts context is fully
> > +     * initialized.
> > +     */
> > +    if (!ts->pkt)
> > +        return;
> > +
> > +    new_data_packet(section, section_len, ts->pkt);
> > +    ts->pkt->stream_index = ts->epg_stream->index;
> > +    ts->stop_parse = 1;
> > +}
> > +
> >  static void sdt_cb(MpegTSFilter *filter, const uint8_t *section, int
> section_len)
> >  {
> >      MpegTSContext *ts = filter->u.section_filter.opaque;
> >      MpegTSSectionFilter *tssf = &filter->u.section_filter;
> >      SectionHeader h1, *h = &h1;
> >      const uint8_t *p, *p_end, *desc_list_end, *desc_end;
> > -    int onid, val, sid, desc_list_len, desc_tag, desc_len, service_type;
> > +    int onid, val, sid, desc_list_len, desc_tag, desc_len, service_type,
> > +        eit_sched, eit_pres_following;
> >      char *name, *provider_name;
> >
> >      av_log(ts->stream, AV_LOG_TRACE, "SDT:\n");
> > @@ -2534,6 +2591,13 @@ static void sdt_cb(MpegTSFilter *filter, const
> uint8_t *section, int section_len
> >          val = get8(&p, p_end);
> >          if (val < 0)
> >              break;
> > +        eit_sched = (val >> 1) & 0x1;
> > +        eit_pres_following = val & 0x1;
> > +
> > +        if ((eit_sched | eit_pres_following) && !ts->epg_stream)
> > +            av_log(ts->stream, AV_LOG_WARNING, "SDT table advertise EIT
> but no"
> > +                   " packets were received yet.\n");
> > +
>
> You should remove this, there are tons of captures where EIT PID is
> intentionally filtered, we should not spam the user.
>
> >          desc_list_len = get16(&p, p_end);
> >          if (desc_list_len < 0)
> >              break;
> > @@ -2984,8 +3048,8 @@ static int mpegts_read_header(AVFormatContext *s)
> >          seek_back(s, pb, pos);
> >
> >          mpegts_open_section_filter(ts, SDT_PID, sdt_cb, ts, 1);
> > -
> >          mpegts_open_section_filter(ts, PAT_PID, pat_cb, ts, 1);
> > +        mpegts_open_section_filter(ts, EIT_PID, eit_cb, ts, 1);
> >
> >          handle_packets(ts, probesize / ts->raw_packet_size);
> >          /* if could not find service, enable auto_guess */
> > @@ -3240,8 +3304,11 @@ MpegTSContext
> *avpriv_mpegts_parse_open(AVFormatContext *s)
> >      ts->raw_packet_size = TS_PACKET_SIZE;
> >      ts->stream = s;
> >      ts->auto_guess = 1;
> > +    ts->epg_stream = NULL;
>
> Not needed, as context is zero initialized.
>
> > +
> >      mpegts_open_section_filter(ts, SDT_PID, sdt_cb, ts, 1);
> >      mpegts_open_section_filter(ts, PAT_PID, pat_cb, ts, 1);
> > +    mpegts_open_section_filter(ts, EIT_PID, eit_cb, ts, 1);
> >
> >      return ts;
> >  }
> > --
> > 2.23.0
>
> Regards,
> Marton
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