Mark M. Hoffman on 26 Feb 2009 10:23:33 -0800

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Re: [PLUG] mini-HOWTO: mp3fs

Hi Walt, Gabe:

> On Thu, Feb 26, 2009 at 12:08:14PM -0500, gabriel rosenkoetter wrote:
> > I actually question the sanity of doing the flac->mp3 processing on
> > the fly all the time, which entails a non-trivial memory and CPU hit.

My home file server is not CPU bound.  I guess this is not uncommon.  Also, at
128 kb/s encoding, 8 minutes of mp3 is less than 8MB of memory.  No big deal.

> > It may work okay if there's only one or two readers, but it can't
> > scale without some fairly clever pre-fetch and (fast) disk caching.
> > That said, it's perfect for what it's intended to do (but don't
> > imagine that you could use this to drive, for example, 25 listening
> > stations in a record store without throwing some beefy hardware at
> > it).

25 streams of FLAC without mp3fs would be equally hard on the disk, no?

* Walt Mankowski <> [2009-02-26 12:14:42 -0500]:
> You're also going to take a big hit the first time you try to sync it
> with a new device, but you'd take that anyway.  I'm a little curious
> how you avoid taking that hit every time you sync -- if it just uses

Where "it" is the consumer device, yes?

> timestamps, that's fine.  But if it uses something like an md5
> checksum, it's not going to work all that well.

Depends on the read/write speed of the device, too.  They're not usually all
that fast.  I ran the following on a few different mp3fs files:

	$ time dd if=blah.mp3 of=/dev/null

I get about 340 kB/s throughput with an Intel Core2 6600.  I'll have to compare
that against the speed of my wife's ipod later.

One downside of this filesystem involves the id3 tags... a lot of software will
just open every file in a directory and read just enough to process all of the
tags at once.  It looks like older versions of mp3fs didn't handle this well,
but the current version does much better.

Also: if you immediately skip to the middle of a song you're going to wait for
a second or five while the encoder catches up.  It's the nature of the beast I
guess.  More CPU will make this problem go away also.

So yeah, it's not perfect... but I find it to be a reasonable tradeoff.  A big
factor for me is that I get so much stuff in FLAC format to begin with.  E.g.


Mark M. Hoffman

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