[Ffmpeg-devel] Mpeg2-ts encoder uses fixed PES payload size

[Måns Rullgård]

Michael Niedermayer <michaelni at gmx.at> writes:

> Hi
>
> On Sun, Mar 04, 2007 at 01:33:23PM +0000, M?ns Rullg?rd wrote:
>> Michael Niedermayer <michaelni at gmx.at> writes:
>> 
>> > Hi
>> >
>> > On Sat, Mar 03, 2007 at 07:06:39PM +0100, Luca Abeni wrote:
>> >> Hi all,
>> >> On Sat, 2007-03-03 at 18:56 +0100, Luca Abeni wrote:
>> >> [...]
>> >> > Ok, here is the patch. 
>> >> [...]
>> >> Sorry, I sent a wrong patch. Here is the correct one.
>> >
>> > i would prefer if the sdt placement frequency could be selected by the
>> > user instead of haveing a dummy muxer which doesnt place SDTs
>> > but mans is maintainer not me so its his decission ...
>> >
>> > if the placement becomes user selectable then we also must decide
>> > about  the units of the new parameter (sdt per time vs. sdt per
>> > bits) without looking at the mpeg spec i would guess per time is
>> > more correct
>> 
>> With a quick glance at the DVB specs, all I find about SI repetition
>> rates is a minimum interval of 25ms between repetitions.
>> 
>> BTW, why do we generate SDT at all?  It is a DVB extension, and would
>> only be useful to someone creating a transport stream for broadcast,
>> for which purpose the current lavf ts muxer is useless.  A proper DVB
>> transport stream also needs the other DVB SI tables, which we do not
>> create.
>
> well you are our mpeg (de)muxing expert and maintainer ...
>
> also it seems the SDT stuff has been there since the initial checkin of
> mpegtsenc.c so i fear only fabrice knows why its there ...
>
> ive no objections to simply disabling it if you say its useless ...

The SDT contains the name and some other parameters related to the TV
channel (service), most of which do not make sense in a non-broadcast
context.

Including support for the SI tables in a demuxer makes sense, since
it is useful when processing recorded DVB streams.

The lavf muxer writes an SDT setting the service name to the title
from the format context.  This wrong, that field being supposed to
contain the name of the channel, such as "BBC 1".  The title belongs
in an EIT section.

As I doubt anyone is depending on the SDT we're writing, I'm tempted
to simply remove it entirely.  Should someone like to implement full
DVB SI support, I won't oppose, but I'm not going to do it myself just
now.

-- 
M?ns Rullg?rd
mans at mansr.com