[CELT-dev] adding celt support to netjack some questions.

torbenh at gmx.de torbenh at gmx.de
Tue Nov 25 01:42:04 PST 2008

On Tue, Nov 25, 2008 at 08:36:39AM +0100, "Alexander Car?t" wrote:
> Hi all,
> > ok... i guess i will implement this later.
> > is support for more then 512 sample blocks planned ?
> > i am putting one jack period of data into one packet.
> > so currently it only works with a period of <=512.
> > i could split that myself. but i dont see why the API should not handle
> > bigger blocks. and just hide the splitting to smaller blocks.
> +1 ---  I do something similar to netjack (currently called "Soundjack") in order to play live music on a network ( https://www.itm.uni-luebeck.de/users/carot/TMT08.pdf ).
> My settings vary from 1024 down to 128 sample-blocks (depending on the current network situation). CELT works excellent in that context but it would be nice to have 1024 samples supported as well.
> > i need to fix alsa_in and alsa_out now, because they dont handle the big
> > timing jitter of an internet connection gracefully.
> I`d be curious to know what you are approaching to change in that context. What amount of packets do you normally buffer on the network input in order to cope with the jitter ?

i mainly only fixed the segfaults which occured in alsa_in and alsa_out.
and made them RT-safe finally.

the netjack approach is somewhat different. it operates synchronised to
only one soundcard. the slave machine has to use alsa_in and alsa_out to
connect to the soundcard.

these tools use the soundcard dma buffer as "jitter buffer"
they work very well under low jitter conditions, as seen, when using
netjack with ethernet. i normally use 1024 samples as buffer.

the internet is a new use case. i discovered celt yesterday.
and just started testing with internet.
alsa_out was already quite robust on a berlin <-> new york connection.
of course its hitting buffer boundaries sometimes.
but the other end is not seeing these problems. because of the
synchronous operation.

paul davis told me about your software. you demoed it on Tonmeister
Tagung, right ?

torben Hohn

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