[linux-dvb] Re: video pts differences on dvb-t in the uk

["Robert Schlabbach" <robert_s@gmx.net>]

From: "Måns Rullgård" <mru@mru.ath.cx>
> "Robert Schlabbach" <robert_s@gmx.net> writes:
> > FWIW, I have been toying with writing a simple TS-to-PS converter
> > which simply outputs a pack_header() each time a PCR is received
> > (with the PCR time stamp as the SCR one) and then simply outputs
> > PES packets whenever one has been completely received.
>
> Remember that TS allows a size of 0 to be specified in the PES header,
> meaning that the PES packet can be arbitrarily large, the end being
> indicated by the start of the next PES packet as marked by the
> unit_start_flag in the TS header.

Maybe I should have mentioned that the files created this way _can_ be
played back! Yes, I'm aware of the PES header length field. It turned out
that the field is correctly filled in for the audio streams (you may have
noticed that there were two audio streams in the sample I've shown, an
MPEG-2 and an AC-3 one), but has 0 in the length field for the video PES
packets. I filled that field in after receiving the packet completely, but
this occasionally didn't work, because the transmitted packets were up to
128KB in size, while the PES length field only allows up to 64KB sizes. So
obviously, you have to remultiplex the streams correctly, best using
DVD-compatible 2KB packet sizes.

But the point here was just that audio packets are indeed commonly
transmitted late (or so it seems). I should also have mentioned that the
sample was taken from the ASTRA satellites at 19.2°E, on the 12.480GHz
transponder, recording PIDs 0xFF (video/PCR), 0x100 (audio MPEG-2) and
0x101 (audio AC-3).

So it is not just DVB-T in some countries, it can also be observed on
DVB-S.

Regards,
--
Robert Schlabbach
e-mail: robert_s@gmx.net
Berlin, Germany