Subject: Re: [linux-audio-dev] multi-track audio files - what format ?
From: Paul Barton-Davis (pbd_AT_Op.Net)
Date: to loka 07 1999 - 19:40:10 EDT
>> OK, so to my disappointment, Michael Pruett's libaudiofile, just like
>> its SGI counterpart, doesn't support multi-track files. Does anyone
>> have any advice on file formats that support non-interleaved,
>> multi-track sound ?
>
>Non-interleaved? Why not just use multiple conventional files (mono or
>stereo) which get read or written in parallel?
Looks like this will have to be the way for now. But this sucks from
the application/user point of view. I want my recording session
bundled up in a single file, not 2 or 3 or 17 files.
>But why wouldn non-interleaved be better performance? Wouldn't you have
>to bounce around the disk more?
well, now that i think about it, what with fs prefetching and all,
yes, you might be right for the read case. but for writing, it means
all kinds of lseek() calls if we just want to overwrite a single track
so that we can write single samples.
however, because the mixer doesn't do this (rewrite a single track),
its cheap enough for now. to be honest even if it did, it would be
reading the file in as a series of chunks, then do pointer skips
rather than lseeks() to reset the data for a given track, and then a
final write(2) of a chunk. its only in the case of wanting to
overwrite a track without reading the file first that the interleaving
will cost, right ?
[ ... unanswerable philosophy elided ... ]
--p
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