Subject: Re: [linux-audio-user] SAOL/MP4 question
From: Brian Redfern (bredfern_AT_calarts.edu)
Date: Thu Jul 04 2002 - 02:44:16 EEST
Yikes, sfront can do waaay more than I thought, I have to take advantage
of my long weekend and read through the sfront manual. I've messed with
Csound, but found its tough to compile on linux (when I switched from
windows 2 years ago), and thought that sfront was just trying to replicate
some of csound's functionality, but I'm really wrong, I didn' understand
that mp4 isn't compressed audio, somehow I was under the wrong impression
that you just output a compressed audio. I didn't realize that its similar
to the old mod file format, but several steps beyond that as well. Very
cool.
On Wed, 3 Jul 2002, John Lazzaro wrote:
> > Brian Redfern writes:
> >
> > As far as I know, those files are used by sfront to create a c program
> > that then generates an mp4, but those files themselves are part of sfront,
> > not mp4 itself.
>
> Just to clarify here ...
>
> The "mp4" files really do act as containers for these different files.
> And so, you can place file types into, and also extract them out. An
> example:
>
> Let's look at the "sfront/examples/src1" example that ships with sfront.
>
> % pwd
> /home/cs/lazzaro/s81/examples/scr1
> % ls
> Makefile core/ samp_1.aif scr1.mid scr1.saol scr1.sasl
>
> Let's make a (pseudo, since saolc and sfront pre-date true MPEG mp4 files)
> mp4 file using sfront:
>
> sfront -orc scr1.saol -sco scr1.sasl -midi scr1.mid -bitout scr1.mp4
>
> % ls
> Makefile core/ sa.c samp_1.aif scr1.mid scr1.mp4 scr1.saol scr1.sasl
>
> This scr1.mp4 file is basically a binary encapsulation of the three
> constituent files. The SAOL and SASL files are token-encoded, and
> so the size goes down a bit, but the MIDI and AIF file are encoded
> directly. We can see this by looking at all of the file sizes:
>
> -rw-rw-r-- 1 lazzaro brass 14 May 24 17:52 scr1.sasl
> -rw-rw-r-- 1 lazzaro brass 3752 May 24 17:52 scr1.saol
> -rw-rw-r-- 1 lazzaro brass 11704 May 24 17:52 scr1.mid
> -rw-rw-r-- 1 lazzaro brass 303754 May 24 17:52 samp_1.aif
> -rw-rw-r-- 1 lazzaro brass 316847 Jul 3 15:21 scr1.mp4
>
> We can extract these constituent files out by using this command:
>
> sfront -bit scr1.mp4 -orcout tmp.saol -scoout tmp.sasl -midout tmp.mid
>
> -rw-rw-r-- 1 lazzaro brass 303744 Jul 3 15:25 a41.wav
> -rw-rw-r-- 1 lazzaro brass 17 Jul 3 15:25 tmp.sasl
> -rw-rw-r-- 1 lazzaro brass 2694 Jul 3 15:25 tmp.saol
> -rw-rw-r-- 1 lazzaro brass 11704 Jul 3 15:25 tmp.mid
>
>
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