gstmpegtsdemux: add temporary **HACK** for dvb subs testing so dvbsuboverlay gets...

gstmpegtsdemux: add temporary **HACK** for dvb subs testing so dvbsuboverlay gets whole packets

<tpm> leio, what's the mpegts demux hack about?
<leio> my libdvbsub code can't handle cut packets
<leio> so the hack instructs the demuxer to gather full packets before pushing down, but it applies that to more PES packet types than just dvbsub, but I'm not sure if that's a bad thing
<leio> either way, needs a cleaner solution, either in demuxer, or I need to handle cut packets
<tpm> ok, but really it should be fixed in the overlay, right?
<tpm> or a parser be inserted
<leio> the problem is that I don't know from the first packet beforehand if it is a cut one or no
<leio> not
<leio> err, first buffer
<leio> just when I receive the next one I see if it has a valid timestamp on it or not
<leio> so I can't very well queue it up in the chain either, I might be blocking the very last subtitle for no reason or something
<tpm> but you could just drop/ignore packets until you find one, right?
<leio> find what?
<tpm> a complete packet?
<leio> the problem isn't that they aren't complete
<leio> the problem is that they are cut across multiple GstBuffers by the demuxer without the hack
<tpm> sure, I understand that
<tpm> but you can't easily determine if a GstBuffer contains he start fragment of a packet or not?
<leio> I guess I could parse the packet and see if its length is enough, just like the libdvbsub code eventually does too
<leio> I can, it has a timestamp if it's the first chunk
<leio> I just never know if I need to wait for more, without some parsing
<tpm> ah ok
<leio> while the demuxer could just give me an uncut one in the first place
<leio> like it always does for program streams
<leio> that gather_pes is always set in gstmpegdemux, but not in gstmpegtsdemux