[linux-dvb] Re: Reading in 188 byte chunks?

[Josef Wolf <jw@raven.inka.de>]

On Thu, Nov 25, 2004 at 11:09:39PM +0100, Johannes Stezenbach wrote:

Thank you for the clarifications, Johannes.  I start to see some light
at the end of the tunnel, but I am still pretty much confused :)

> 188 byte is the lenght of a TS packet. PES packets have variable
> length, as do sections.

But PES packets (requested with DMX_SET_PES_FILTER) come in 188 byte
packets.  So they are repacked in a TS?

> Section data is normally low-bandwidth, so the API does the right thing
> to simplify section handling.

So "sections" do not contain audio/video data (since a/v is high-bandwidth)?
I am primarily interested in receiving audio/video.  Should I forget about
the "sections"?

> For PES we don't support a packet interface at all, instead
> we output a payload-only byte stream (i.e. TS header and adaptation
> field stripped); applications must search for PES start code
> themselves.

Can you please describe this in more detail?  I definitely get 188 byte
packets with leading 0x47 sync and the PID contained in second+third byte,
so the TS header is _not_ stripped for me?

When requesting multiple channels, how do I know which channel a packet
belongs to when the TS-header is stripped?

BTW: Do I understand correctly that I can not request multiple channels
with DMX_SET_FILTER?  What are the "filter" and "mask" entries in
dmx_filter_t?  I can not find any indication what this is good for...

> http://212.227.36.83/linuxtv/wiki/index.php/MPEG2_Standard

Thanks for the link.  Lots of information there.  But it's pretty hard to
sort it out :)

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-- Josef Wolf -- jw@raven.inka.de --