Subject: Re: [linux-audio-dev] Re: streaming from disk to terminatorX added (via mmap)
From: Alexander König (alex_AT_rhlx01.fht-esslingen.de)
Date: ma loka 25 1999 - 22:57:09 EDT
Paul Barton-Davis wrote:
> just FYI: my C++ libsoundfile uses mmap(), but still requires
> applications to "read" the data. it is significantly faster than using
> read(2) internally, however, so there might be an argument for using
> mmap regardless of the endianness, and then using arch-dependent
> macros to fetch the data from the mmapped area. for example, on a
> little endian machine reading from a little endian RIFF/WAV file, the
> macros are essentially no-ops.
No-ops? Do you mean you don't generate ANY code for this? If so: HOW?
<..>
> >- the next release of tX will allow you to load MANY (as many as you
> >want) samples in multiple turntables. If all these are mmap'ed files I
> >guess your disk-head will jump around like mad when playing.
>
> actually, no more than it would if you use a 4K memory buffer :)
??? Yeah sure, using a limited buffer will have the same effect but the
way tX currently does it is like the good ole trackers did it: it loads
the samples COMPLETELY in RAM so there is no disk-activity at all while
playing....
> >- With 6 to 8 tables playing my system is pretty loaded in these cases
> >it might be a performance win to have the samples in the memory
> >already.. (well these are just assumptions - we should get your code
> >applied to the new stuff to see whether it's true...)
>
> benno's code makes sure it *is* in RAM already. just not all of it
> at one time.
Yeah, you are right. I guess what I wanted to say was: If you mmap()
files instead of loading there's a lot of other stuff happening aside
for audio-rendering (you know like mmap()-code, fs-code, ide-code...)
Now if you have a lot of turntables and some effects enabled your CPU
may be pretty busy getting the audio ready for playback and that
additional code may be too much.. well still: it's just an assumption ;)
Bye, Alex
--
_______________________________________________________________________
Alexander König - alex_AT_42.fht-esslingen.de
http://termX.cjb.net
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