Re: I/O Error in mmapping ES 1969

[Paul Davis <paul@linuxaudiosystems.com>]

>I mentioned my ham radio realtime program with mmap
>in a posting on 3. Oct and before.
>It works now with ALSA 0.9.7 with AC97 and maybe some other cards, thanks!!!
>With ESS ES1969 mmap(ibuf, isize, PROT_READ, MAP_FILE | MAP_SHARED | 
>MAP_FIXED, fd_audio, 0)
>(and I tried also all other MAP_ options) it breaks with I / O error.
>Do You know some help about mmap besides man,

IIRC, mmap with OSS doesn't work unless you use the LD_PRELOAD
hack. this loads a library that intercepts all standard system calls
and routes them through alsa-lib. your app will not run without
this. why? mmap provides direct access to the DMA buffer of the
hardware, and thus bypasses most of what alsa-lib does. ALSA does
support such direct access, but not in the simplistic way that OSS
provides.

or can I do something with "Scatter Gather" in ALSA API,
>or does it help if i work myself into JACK for this problem?
>hints welcome, tnx!!!

either use ALSA natively, or use JACK, or use the LD_PRELOAD hack.


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