[linux-dvb] Re: demux.h version trouble

[Ralph Metzler <rjkm@convergence.de>]

Felix Domke writes:
 > some hardware (i'm thinking of the Avia-GTX/DMX for which i currently (try
 > to :) implement the nokia-api) does not allow to specify which queue (=feed)
 > it uses to get the data from that is sent to the decoder.
 > 
 > for example, on the Avia-GTX/DMX the first queue is always the video-queue,
 > the second one the one for audio and the third the one for teletext-data.
 > 
 > At the moment i have a 1:1-mapping for the feed <-> queue. And here lies the
 > problem: at the moment where dmx->allocate_ts_feed is called, i search for a
 > free queue for the new feed. Later on "set_type" is called - but at that
 > time, i would have to re-allocate the queue, since i did not know at the
 > allocate-time that it has to be a "special" (audio/video/teletext)-queue.
 > 
 > So i had to change the feed, but that's not possible. maybe - but that's
 > only a quick hack - it's possible to change
 > int (*set_type) (struct dmx_ts_feed_s* feed, int type, dmx_ts_pes_t
 > pes_type);
 > to
 > int (*set_type) (struct dmx_ts_feed_s** feed, int type, dmx_ts_pes_t
 > pes_type);
 > which would allow set_type to change the feed. another way - which wouldn't
 > break the current api - would be to implement another layer for the
 > feed->queue-mapping. if this problem is special to the avia-chipset, i would
 > implement it that way, but it would be nice if the allocate_ts_feed-call
 > include flags with the wanted "features" for that new feed.
 > 
 > if i read it right, it would just be a small change in dmxdev.c.

The AV7110 does not have the special PID restriction but the firmwares
filtering code already reserves PIDs for audio and video. So, I just used
the layer already provided by the firmware as the second layer you describe
above. A direct implementation of the API on the AV7110 chip would
not need this but I also did not want to change the allocation
function because it would break source compatibility.

Another alternative would of course be to provide a new
allocation call which provides the old and the set_type-features and also
to keep the old allocation call around for compatibility.

 > another question:
 > 
 > you use a DMX_TS_PES_PCR. Normally the video-stream carries the PCR-Data, so
 > wouldn't it be better to include a flag like "use this feed for PCR"? or did
 > i miss something?

Hmmm, good question. I'll have to ask the people at Nokia who thought
this part up.
It would make more sense if a PCR flag would be or-able to the other settings.

Ralph 


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