[mythtv] [PATCH] Big DVB Patch V3.5 - MPEG TS

Tim Davies tim at opensystems.net.au
Tue Jan 11 18:12:20 EST 2005

Right, timezones suck!  Sleeping while everyone else is awake is a pain in
the butt...

Chopping up about 5 emails here:

> Are you using SPDIF passthrough? If you are not, i.e using software AC3,
> then
> the audio rates and channels will be differenent between stations which
> will
> be enough for check audio params function to pick up the changed audio
> type
> and re-initialise. When using SPDIF passthrough the audio is set to 2
> channel
> 48000, which also happens to be what we get from the mpeg audio, and so a
> test on rate and channel is not enough to detect the changed audio type.
> This
> mught explain why I need the incCurrentAdio stream change and you do not.
> I'll have a look to see if there is a smater way to do this that will work
> with both.

Yes, I'm using software AC3.  I've been holding off buying a receiver until
this code works (strangely enough).  It's interesting that incrementing the
current audio stream causes mine to freak out.

> Yeah, the current descriptor handling is kinda quick and dirty. I
> haven't analyzed the patch that deeply, but I don't think it is safe. I
> tried using dynamically allocated memory at first too, but since we are
> storing it inside a QT object which gets passed around and copied and
> what not, we end up with several copies of the object which all point to
> the same memory. When the destructors are called, the first one will
> destroy the data and the other objects are left with undefined data at
> best and probably a segfault.
> I think we should create a new "Descriptor" object which can be stored
> in a QValueList DescriptorList or something. That object then needs to
> ensure that if the object is cloned, the data is cloned as well. Opinions?

Yep, agree on that one.  I was getting hairs on the back of my neck standing
on end as I wrote the reallocs...

> You can look at the CreatePMT() in dvbrecorder.cpp code and its possible
> changing the one line where (*es).Orig_Type is written to the PMT to
> something
> like this.
> if ((*es).Type == ES_TYPE_AUDIO_AC3)
>     pmt[p++] = 0x81;
> else
>     pmt[p++] = (*es).Orig_Type;
> Give this a shot and let me know if this solves your issues..

I'll take any advice on this one.  I just worked back from mpegts.c and
found that not all descriptors where making it through.  I'm happy to do the
"hack" in dvbrecorder.cpp.

> Yeah, but anyway, that is another issue and not really related to Tim's
> AC3 patch. The PMT stream type fix should be perfectly safe but I'm not
> sure if that's enough for AC3 to work or if the other parts of the patch
> (descriptors, avformatdecoder and mpeg hack) are needed as well...?


- Reading all the descriptors was needed to identify that the private stream
was actually AC3.
- The audio track changing code in Mark's patch is used, but the
mpeg.c/transform.c hacks are not.

So where are we on this?  Sorry, I still haven't woken up yet...brain not


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