From fiji at ayup.limey.net  Mon Sep 15 05:46:13 2008
From: fiji at ayup.limey.net (Ben Bennett)
Date: Mon, 15 Sep 2008 08:46:13 -0400
Subject: [ID3 Dev] synchsafe integers
In-Reply-To: <9f47d5f70809150105r48314c74q45d62f861f9d1189@mail.gmail.com>
References: <48CB762A.8070202@gmx.de> <9f47d5f70809150105r48314c74q45d62f861f9d1189@mail.gmail.com>
Message-ID: <20080915124613.GA14923@ayup.limey.net>

On Mon, Sep 15, 2008 at 01:35:01PM +0530, Dhanraj Birader wrote:
>  If bit 7 is zero then keep it as it is.

No!  Otherwise you can not correctly convert back since multiple
synchsafe ints would map to the same number.


> On Sat, Sep 13, 2008 at 1:43 PM, Daniel Wechsler <daaaaaaniel at gmx.de> wrote:
> > Bit 7 must always be 0, so 1111 1111 becomes 0000 0001  0111 1111.
> >
> > But what is if bit 7 is already 0? Do I have to add a 0, too? [0000 0001
> >  0111 1111 -> 0000 0010  0111 1111]

Yes.  That is correct.

Before Conversion      After Conversion
--------------------   --------------------
0000 0000  1111 1111   0000 0001  0111 1111
0000 0001  0111 1111   0000 0010  0111 1111   

If you did not convert the second one, then you would be unable to
tell what '0000 0001  0111 1111' mapped to.

     	  Hope that helps.

     	  	      -ben

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From daaaaaaniel at gmx.de  Sat Sep 13 01:13:30 2008
From: daaaaaaniel at gmx.de (Daniel Wechsler)
Date: Sat, 13 Sep 2008 10:13:30 +0200
Subject: [ID3 Dev] synchsafe integers
Message-ID: <48CB762A.8070202@gmx.de>

Hello out there, I'm new here!

My question concerns the synchsafe integers, which were used for saving 
the tag- and framesize.
Bit 7 must always be 0, so 1111 1111 becomes 0000 0001  0111 1111.

But what is if bit 7 is already 0? Do I have to add a 0, too? [0000 
0001  0111 1111 -> 0000 0010  0111 1111]
Or stays it like it is?

(I'm sorry for my bad english, I'm from Germany^^)
Thank you, Daniel

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From jmartin_92 at verizon.net  Sat Sep 13 01:24:38 2008
From: jmartin_92 at verizon.net (Jim)
Date: Sat, 13 Sep 2008 04:24:38 -0400
Subject: [ID3 Dev] synchsafe integers
In-Reply-To: <48CB762A.8070202@gmx.de>
References: <48CB762A.8070202@gmx.de>
Message-ID: <48CB78C6.5010303@verizon.net>

Daniel Wechsler wrote:
> Hello out there, I'm new here!
> 
> My question concerns the synchsafe integers, which were used for saving 
> the tag- and framesize.
> Bit 7 must always be 0, so 1111 1111 becomes 0000 0001  0111 1111.
> 
> But what is if bit 7 is already 0? Do I have to add a 0, too? [0000 
> 0001  0111 1111 -> 0000 0010  0111 1111]
> Or stays it like it is?
> 
> (I'm sorry for my bad english, I'm from Germany^^)
> Thank you, Daniel


Yes, you have it right.  In a synchsafe integer, only bits 0 thru 6 are used. 
You do need to shift that zero from bit 7 to bit 0 of the next byte.  Otherwise 
the synchsafe integer will not be properly decoded.



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From mark at maseurope.net  Mon Sep 15 07:26:20 2008
From: mark at maseurope.net (Mark Smith)
Date: Mon, 15 Sep 2008 15:26:20 +0100
Subject: [ID3 Dev] synchsafe integers
In-Reply-To: <20080915124613.GA14923@ayup.limey.net>
References: <48CB762A.8070202@gmx.de> <9f47d5f70809150105r48314c74q45d62f861f9d1189@mail.gmail.com> <20080915124613.GA14923@ayup.limey.net>
Message-ID: <026BDD0C-E9F9-40DC-912B-1F86EE1FD220@maseurope.net>

It helped me to consider that a sync-safe integer is a 28 bit int,  
that is stored in a 32 bit container, such that bits 7, 15, 23 and 31  
are always cleared, and not used in the representation of the number.

Best,

Mark
On 15 Sep 2008, at 13:46, Ben Bennett wrote:

> On Mon, Sep 15, 2008 at 01:35:01PM +0530, Dhanraj Birader wrote:
>>  If bit 7 is zero then keep it as it is.
>
> No!  Otherwise you can not correctly convert back since multiple
> synchsafe ints would map to the same number.
>
>
>> On Sat, Sep 13, 2008 at 1:43 PM, Daniel Wechsler  
>> <daaaaaaniel at gmx.de> wrote:
>>> Bit 7 must always be 0, so 1111 1111 becomes 0000 0001  0111 1111.
>>>
>>> But what is if bit 7 is already 0? Do I have to add a 0, too?  
>>> [0000 0001
>>>  0111 1111 -> 0000 0010  0111 1111]
>
> Yes.  That is correct.
>
> Before Conversion      After Conversion
> --------------------   --------------------
> 0000 0000  1111 1111   0000 0001  0111 1111
> 0000 0001  0111 1111   0000 0010  0111 1111
>
> If you did not convert the second one, then you would be unable to
> tell what '0000 0001  0111 1111' mapped to.
>
>      	  Hope that helps.
>
>      	  	      -ben
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: id3v2-unsubscribe at id3.org
> For additional commands, e-mail: id3v2-help at id3.org
>


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From dhanraj at nextbitcpu.com  Mon Sep 15 01:05:01 2008
From: dhanraj at nextbitcpu.com (Dhanraj Birader)
Date: Mon, 15 Sep 2008 13:35:01 +0530
Subject: [ID3 Dev] synchsafe integers
In-Reply-To: <48CB762A.8070202@gmx.de>
References: <48CB762A.8070202@gmx.de>
Message-ID: <9f47d5f70809150105r48314c74q45d62f861f9d1189@mail.gmail.com>

Hi,

 If bit 7 is zero then keep it as it is.

regards
Dhanraj.

On Sat, Sep 13, 2008 at 1:43 PM, Daniel Wechsler <daaaaaaniel at gmx.de> wrote:

> Hello out there, I'm new here!
>
> My question concerns the synchsafe integers, which were used for saving the
> tag- and framesize.
> Bit 7 must always be 0, so 1111 1111 becomes 0000 0001  0111 1111.
>
> But what is if bit 7 is already 0? Do I have to add a 0, too? [0000 0001
>  0111 1111 -> 0000 0010  0111 1111]
> Or stays it like it is?
>
> (I'm sorry for my bad english, I'm from Germany^^)
> Thank you, Daniel
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: id3v2-unsubscribe at id3.org
> For additional commands, e-mail: id3v2-help at id3.org
>
>
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From dhanraj at nextbitcpu.com  Tue Sep 16 01:41:25 2008
From: dhanraj at nextbitcpu.com (Dhanraj Birader)
Date: Tue, 16 Sep 2008 14:11:25 +0530
Subject: [ID3 Dev] synchsafe integers
In-Reply-To: <20080915124613.GA14923@ayup.limey.net>
References: <48CB762A.8070202@gmx.de>
	 <9f47d5f70809150105r48314c74q45d62f861f9d1189@mail.gmail.com>
	 <20080915124613.GA14923@ayup.limey.net>
Message-ID: <9f47d5f70809160141n4b9963acmae40ea12d61bf548@mail.gmail.com>

Ya u r right because while extracting we need to extract only 28bits.

Thank u........
regards
Dhanraj biradar

On Mon, Sep 15, 2008 at 6:16 PM, Ben Bennett <fiji at ayup.limey.net> wrote:

> On Mon, Sep 15, 2008 at 01:35:01PM +0530, Dhanraj Birader wrote:
> >  If bit 7 is zero then keep it as it is.
>
> No!  Otherwise you can not correctly convert back since multiple
> synchsafe ints would map to the same number.
>
>
> > On Sat, Sep 13, 2008 at 1:43 PM, Daniel Wechsler <daaaaaaniel at gmx.de>
> wrote:
> > > Bit 7 must always be 0, so 1111 1111 becomes 0000 0001  0111 1111.
> > >
> > > But what is if bit 7 is already 0? Do I have to add a 0, too? [0000
> 0001
> > >  0111 1111 -> 0000 0010  0111 1111]
>
> Yes.  That is correct.
>
> Before Conversion      After Conversion
> --------------------   --------------------
> 0000 0000  1111 1111   0000 0001  0111 1111
> 0000 0001  0111 1111   0000 0010  0111 1111
>
> If you did not convert the second one, then you would be unable to
> tell what '0000 0001  0111 1111' mapped to.
>
>          Hope that helps.
>
>                      -ben
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: id3v2-unsubscribe at id3.org
> For additional commands, e-mail: id3v2-help at id3.org
>
>
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From daaaaaaniel at gmx.de  Sat Sep 13 01:25:27 2008
From: daaaaaaniel at gmx.de (Daniel Wechsler)
Date: Sat, 13 Sep 2008 10:25:27 +0200
Subject: [ID3 Dev] synchsafe integers
In-Reply-To: <48CB78C6.5010303@verizon.net>
References: <48CB762A.8070202@gmx.de> <48CB78C6.5010303@verizon.net>
Message-ID: <48CB78F7.1060209@gmx.de>

Wow! That's a fast answer! Thank you

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