Re: [linux-audio-dev] Re: Multimedia compression

Re: [linux-audio-dev] Re: Multimedia compression

[John Lazzaro]

> OTOH, one way to achieve great compression with little distorsion would be 
> decomposing the audio stream in it's elementary "instruments", like
> drumset , guitars ,violines , bass etc, and then code a sort of MIDI-like file
> (very short) with the "samples" stored in the stream only once.
>
> I think MP4-SAOL is a step in that direction.

Basically, there's two interrelated research agendas, both of which need
to make it out of the lab for this sort of compression to make it to the
real world: 

[1] Doing the decomposition. The three major ways people are thinking about
solving this problem right now are 

  [A] The mathematical approach -- in a nutshell "Let's separate out N 
      signals from one, under the assumption that the best separation
      makes each separated signal carry unique information. The best
      starting point for understanding how these folks think about 
      the problem is:

      http://www.cnl.salk.edu/~tony/ica.html

      While many of these papers think in terms of "N microphones to 
      listen to a performance of N instrumentalists" as the starting
      signal, this is just to make the math easier -- in practice the
      ideas can be extended to the more general case.

  [B] Auditory scene analysis -- in short, take the analogy from computer
      vision, where raw camera (or retina) output gets broken up into 
      different "maps" coding motion, color, shape, ect, and apply it 
      to audition. These maps should (in theory) make the process of 
      doing separation a lot easier. The good initial resource for
      this approach is:

      http://sound.media.mit.edu/~dpwe/AUDITORY/

  [C] Get access to the 24-track master tapes (uh, I think I just dated
      myself :-), and avoid the whole decomposition problem. Technically
      easy, of course, but might not be practical.

[2] Once you've done the decomposition, create encoders specialized for
specific types of sounds. For certain types of specialized sounds, this
field is very mature (i.e. spoken speech). For other types of sounds,
though, you're basically going to have to

   [1] Look at the best music synthesis algorithms for the sound type,
       and see how easily the algorithm can be "inverted".

   [2] Hope a speech codec works well on the sound (there are a few 
       codecs specialized for singing voice that take this approach ...).

   [3] Do original research on the problem.


One big problem with a field like this is that its hard to get people
motivated to work on the "little problems" described above, if its 
unclear how success on the little problem is going to solve any big 
problem. The hope with Structured Audio is to solve this "meta-problem" --
by having a fielded platform out there, ready to support new approaches
to sound encoding in pilot applications, SA will help motivate research
in the whole area.

In particular, the politics of MPEG is very different than the politics
of IETF -- "joining the process" of creating a new coding standard is
a deep committement of time and resources and money in MPEG-land (note
that I'm not an MPEG member, so I'm outside the process, largely because
of the committment it takes to meaningly participate). But implementing a
new codec _in_ Structured Audio is a whole different ballgame -- you could
get a team together under the rubric of the IETF, or you could just take
the traditional Free Software approach and start a grass roots effort like
LAD. You don't need anyone's permission to write a SAOL program ...

									--jl

-------------------------------------------------------------------------
John Lazzaro -- Research Specialist -- CS Division -- EECS -- UC Berkeley
lazzaro [at] cs [dot] berkeley [dot] edu     www.cs.berkeley.edu/~lazzaro
-------------------------------------------------------------------------

Re: [linux-audio-dev] Re: Multimedia compression

[Juhana Sadeharju]

>From:	Benno Senoner <sbenno@gardena.net>
>
>I prefer to use MPEG Layer 2 ( MP2) at 384kbit (lossy) which outperforms all
>MP3 based codecs even 320kbit. 

How do you know it? Where I could read tests about it?
I have used layer 3 with 320 kbps for compressing radio and cassette
recordings (both music and sound samples snipped from them), so, most
probably I have used the right compressor. But is layer 3 with 320 kbps
somehow not enough for studio mikes (voice, guitar, etc.) or for digital
synth tracks?

Of course, for compressing the final mix (20-bit or greater) of studio work,
the 16-bit MP3 is not enough. But 16-bit could be enough for individual
sounds, vocals, etc. However, I would not use any MP3 compression for even
those because I would record only with 20-bit A/Ds in studio. I have used
MP3 only because I have nothing better than 16-bit A/Ds. So, what compressor
I could use for 20- or 24-bit material? Should we look at ourself for
20- or 24-bit compressor or can MP3 or AAC handle them (similarly than JPEG
can handle 16-bit/channel images)?

Note that 16-bit is most probably enough for mic recordings, but the
extra bits are needed for having extra room. I would not want to dither
20-bit recording down to 16-bit even it would fit very well.

Juhana

Re: [linux-audio-dev] Re: Multimedia compression

[Benno Senoner]

On Mon, 19 Jun 2000, Juhana Sadeharju wrote:
> >From:	Benno Senoner <sbenno@gardena.net>
> >
> >I prefer to use MPEG Layer 2 ( MP2) at 384kbit (lossy) which outperforms all
> >MP3 based codecs even 320kbit. 
> 
> How do you know it? Where I could read tests about it?
> I have used layer 3 with 320 kbps for compressing radio and cassette
> recordings (both music and sound samples snipped from them), so, most
> probably I have used the right compressor. But is layer 3 with 320 kbps
> somehow not enough for studio mikes (voice, guitar, etc.) or for digital
> synth tracks?
> 
> Of course, for compressing the final mix (20-bit or greater) of studio work,
> the 16-bit MP3 is not enough. But 16-bit could be enough for individual
> sounds, vocals, etc. However, I would not use any MP3 compression for even
> those because I would record only with 20-bit A/Ds in studio. I have used
> MP3 only because I have nothing better than 16-bit A/Ds. So, what compressor
> I could use for 20- or 24-bit material? Should we look at ourself for
> 20- or 24-bit compressor or can MP3 or AAC handle them (similarly than JPEG
> can handle 16-bit/channel images)?

I think Philips MPEGLIB  can encode 24bit files, their MP2 software encoder is
the same used in DMX SAT radio encoders , and other DSP platform.

I say I would prefer MP2 over MP3, because MP3 *WAS DESIGNED* for lower
bitrates. ( 128-192kbit).

Plus consider the fact that MP2 has better random-seek properties
(no long frame dependencies), not to mention higher speed when encoding/decoding
material.

If you ask me, if I were designing a system with the best possible audio
quality  while achieving 1:4 compression I would chose MP2 or alternatively
APT-X  ( http://www.aptx.com/ ) 
Unfortunately APT-X is not available as a software-only CODEC,
it is used in some cinema audio systems (DTS) , and doesn't use perceptual
coding, and has an amazing 2.9ms codec delay at 44.1kHz.
The granularity of editable regions is 80usecs = 2 samples, that means
you can edit an APT-X file with almost the same precision as a PCM file.
ATPX is some kind of ADPCM but which encodes subbands with different
precision to reflect the frequency resolution of the ear.

> Note that 16-bit is most probably enough for mic recordings, but the
> extra bits are needed for having extra room. I would not want to dither
> 20-bit recording down to 16-bit even it would fit very well.
> 
> Juhana

But I guess you are looking at a totally free codec  :-)
therefore there is only MP3 , ISO MP2 encoder and perhaps a good 
VORBIS (the patent-free audio codec which matches MP3 quality)


Benno.

Re: [linux-audio-dev] Re: Multimedia compression

[Dustin Barlow]

I will second Paco's synopsis of Shorten.

I have close to 100 concerts that were compressed using the lossless setting
in Shorten, and they are *exact* copies of the original when decompressed.
You can do an md5sum of the wav file prior to compressing it and it will
match after it is uncompressed later on.

I can typically cut a wave file size in half and it is lossless...I don't
think you
can ask for more then that...at least not yet anyway.  I have not tried to
do lossy compression with Shorten so I cannot comment on it's performance
in the lossy realm...

Another thing is that WinShorten *will* stream shorten files so that you do
not have to convert them to wav to listen to them.  I setup a machine to
do that very thing so that I didn't have to burn my extensive SHN library
to audio CDR or wav file prior to listening.  I haven't found a streaming
version of Shorten for linux, so I grabbed the source code the other day
and am looking into what it would take to do it...shouldn't be to difficult.

~Db

----- Original Message -----
From: <paco@hydrofunk.org>
To: Benno Senoner <sbenno@gardena.net>
Cc: Sergey <harlot@mail.ru>; <linux-sound@vger.rutgers.edu>;
<linux-audio-dev@ginette.musique.umontreal.ca>; John Lazzaro
<lazzaro@CS.Berkeley.EDU>
Sent: Tuesday, June 20, 2000 12:08 PM
Subject: [linux-audio-dev] Re: Multimedia compression


> On Sat, 17 Jun 2000, Benno Senoner wrote:
>
> > I tried shorten some time ago:
> >
> > OTOH, when using lossless compression the gain is sometime minimal,
> > only 20% if you are unlucky.
> > Not much for my taste.
>
> I find this very hard to believe.  Speaking from my own experience, I've
> had nothing but outstanding results with SHORTEN.
>
> I collect live concert bootlegs; recorded on DAT, dumped down onto the
> HDD as WAVs, compressed to SHNs, and burned onto CDs that I listen to.
> I've got nearly 100 such CDs sitting here at my side, and here's the
> stats based on those live concert CDs.
>
> My average song compression 52% savings
> My worst single-song comression 35% savings
> My best single-song compression 60% savings
>
> The main thing I wanted to point out is that I've never had a something
> compress less than 35%.
>
> peace,
> -Paco

Re: [linux-audio-dev] Re: Multimedia compression

[paco]

On Tue, 20 Jun 2000, Dustin Barlow wrote:

> to audio CDR or wav file prior to listening.  I haven't found a streaming
> version of Shorten for linux, so I grabbed the source code the other day
> and am looking into what it would take to do it...shouldn't be to difficult.




Hey... this is fairly new.  Somebody hacked XMMS so that it plays SHN
files directly.  The relevant info is in the text below.

Note that you can also do this:

     paco@hydrofunk.org%> shorten -x <file>.shn - | play -t wav -

from the command line to play a SHN without making the intermediate .WAV
file.  It works fine, but you don't get a nice GUI or the ability to
pause, ffwd, or rewind the audio.

I ahven't checked out the hacked XMMS yet, but it's the talk of the town
on www.etree.org.  


>i386 RPMs and their SRPM are available at:
>
>http://phishphry.hagopian.net/
>
>If anyone wants to build it from the SRPM for other architectures but
>doesn't have a spot to host it I can swing that - contact me off the
list.
>                                                               -Rob
>
>On Mon, 19 Jun 2000, jason wrote:
>
> >
> > [I've been waiting to release this for nearly a week, due to outgoing 
>mail
> > being disabled here.  Which was probably good, since I ran into a
minor
> > problem with the initial release that was easily corrected.  I also 
>wanted
> > to wait until XMMS 1.2.1 was released (which it was just a few moments
> > ago), to ensure compatibility and avoid any possible confusion.]
> >
> > 
>-------------------------------------------------------------------------
> >
> >
> > Hey *nix folks,
> >
> >   I've hacked XMMS to support the playback of .shn files directly from 
>the
> > hard drive, perfect for those with little disk space or patience.  :-)
> > All the info you need is here:
> >
> >   http://sdf.lonestar.org/~jason/xmms-shn/
> >
> > Feedback is welcome.  Enjoy!
> >
> > -jason
> >
> > --------------------------- [ etree@etree.org ] 

Re: [linux-audio-dev] Re: Multimedia compression

[paco]

On Tue, 20 Jun 2000 paco@OhKeePa.Net wrote:
> 
> Hey... this is fairly new.  Somebody hacked XMMS so that it plays SHN
> files directly.  The relevant info is in the text below.
> 
> Note that you can also do this:
> 
>      paco@hydrofunk.org%> shorten -x <file>.shn - | play -t wav -
> 
> from the command line to play a SHN without making the intermediate .WAV
> file.  It works fine, but you don't get a nice GUI or the ability to
> pause, ffwd, or rewind the audio.


Just in case anybody out there isn't familiar with perl, I though I'd send
this email out to help them.  Attached is my script for playing SHNs  out
of directories or off of a CD.

To use it, put it in your path somewhere (make sure it's executable!), and
type:

        shnplay /my/shn/file/directory/or/CDROM/path

That's is.  It will play each file with a ".shn" extention in that
directory without making big WAV files as an intermediate step.

SInce the shorten algorithm is so fast, playing SHN files like this only
uses up about 10% of my CPU. (550MHz Athlon.)

BTW:  it's nice to have a topic on this mailing list aside from "how do I
get this card working" or "is there planned support for this card" and the
like.  Those are all good posts to this list, but we never really have too
many actual discussions about stuff.  We just help each other make the
boxes make noise.

Re: [linux-audio-dev] Re: Multimedia compression

[paco]

Whoops... forgot the attachment....

sorry,
--Paco


On Tue, 20 Jun 2000 paco@rift.hydrofunk.org wrote:

> On Tue, 20 Jun 2000 paco@OhKeePa.Net wrote:
> > 
> > Hey... this is fairly new.  Somebody hacked XMMS so that it plays SHN
> > files directly.  The relevant info is in the text below.
> > 
> > Note that you can also do this:
> > 
> >      paco@hydrofunk.org%> shorten -x <file>.shn - | play -t wav -
> > 
> > from the command line to play a SHN without making the intermediate .WAV
> > file.  It works fine, but you don't get a nice GUI or the ability to
> > pause, ffwd, or rewind the audio.
> 
> 
> Just in case anybody out there isn't familiar with perl, I though I'd send
> this email out to help them.  Attached is my script for playing SHNs  out
> of directories or off of a CD.
> 
> To use it, put it in your path somewhere (make sure it's executable!), and
> type:
> 
> 	shnplay /my/shn/file/directory/or/CDROM/path
> 
> That's is.  It will play each file with a ".shn" extention in that
> directory without making big WAV files as an intermediate step.
> 
> SInce the shorten algorithm is so fast, playing SHN files like this only
> uses up about 10% of my CPU. (550MHz Athlon.)
> 
> BTW:  it's nice to have a topic on this mailing list aside from "how do I
> get this card working" or "is there planned support for this card" and the
> like.  Those are all good posts to this list, but we never really have too
> many actual discussions about stuff.  We just help each other make the
> boxes make noise.
> 
> 





TEXT/PLAIN attachment: perl script for playing SHN files