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<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'>I’d say this
is out of scope for this mailing list. Any how, you can’t just shift a
signed number by 8 (multiplying with 256) without handling the <span
class=SpellE>signedness</span>-bit.<o:p></o:p></span></font></p>
<p class=MsoNormal><span class=SpellE><font size=2 color=navy face=Arial><span
lang=EN-GB style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'>PCM</span></font></span><font
color=navy><span lang=EN-GB style='color:navy;mso-ansi-language:EN-GB'> 16-bit
samples are stored as signed values.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'>Try something
simpler which works first and then optimize your code afterwards.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'><o:p> </o:p></span></font></p>
<p class=MsoNormal><span class=GramE><font size=2 color=navy face=Arial><span
lang=EN-GB style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'>unsigned</span></font></span><font
color=navy><span lang=EN-GB style='color:navy;mso-ansi-language:EN-GB'> char <span
class=SpellE>inSamp</span>;<o:p></o:p></span></font></p>
<p class=MsoNormal><span class=GramE><font size=2 color=navy face=Arial><span
lang=EN-GB style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'>short</span></font></span><font
color=navy><span lang=EN-GB style='color:navy;mso-ansi-language:EN-GB'> s1, <span
class=SpellE>outSamp</span>;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'>s1 = (short) <span
class=SpellE>inSamp</span>;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'>s1 -= 128;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'>s1 *= 256;<o:p></o:p></span></font></p>
<p class=MsoNormal><span class=SpellE><span class=GramE><font size=2
color=navy face=Arial><span lang=EN-GB style='font-size:10.0pt;color:navy;
mso-ansi-language:EN-GB'>outSamp</span></font></span></span><font color=navy><span
lang=EN-GB style='color:navy;mso-ansi-language:EN-GB'> = s1;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'>It’s probably
possible to reduce the complexity of this using <span class=SpellE>bitshifts</span>,
unless you know what you are doing and are in a lot of need for speed I don’t
see the reason.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'>//JT<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'>//JT<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;color:navy;mso-ansi-language:EN-GB'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><span class=GramE><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>----<span
class=SpellE>-Ursprungligt</span> meddelande-----<br>
<b><span style='font-weight:bold'>Från:</span></b> speex-dev-bounces@xiph.org</span></font></span><font
face=Tahoma><span style='font-family:Tahoma'> [mailto:speex-dev-bounces@xiph.<span
class=GramE>org]</span> <b><span style='font-weight:bold'>För </span></b>yaseminyilmaz<br>
<b><span style='font-weight:bold'>Skickat:</span></b> den 15 december 2006
17:46<br>
<b><span style='font-weight:bold'>Till:</span></b> speex-dev@xiph.org<br>
<b><span style='font-weight:bold'>Ämne:</span></b> [Speex-dev] About
"Convert 8->16 bits"</span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
style='font-size:10.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=TR style='font-size:10.0pt;mso-ansi-language:TR'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=TR style='font-size:10.0pt;mso-ansi-language:TR'>Hi everybody,<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=TR style='font-size:10.0pt;mso-ansi-language:TR'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=TR style='font-size:10.0pt;mso-ansi-language:TR'>I have been using
speex-1.2beta1 and my input data is 8-bit unsigned so I know that I should
convert from 8 to 16 bits. I’ve done the convertion as following.<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=TR style='font-size:10.0pt;mso-ansi-language:TR'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt;text-indent:35.4pt;text-autospace:
none'><font size=2 face="Courier New"><span lang=TR style='font-size:10.0pt;
font-family:"Courier New";mso-ansi-language:TR'>for(int i=0; i<160; ++i)<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt;text-indent:35.4pt;text-autospace:
none'><font size=2 face="Courier New"><span lang=TR style='font-size:10.0pt;
font-family:"Courier New";mso-ansi-language:TR'>{<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt;text-autospace:none'><font size=2
face="Courier New"><span lang=TR style='font-size:10.0pt;font-family:"Courier New";
mso-ansi-language:TR'>
input_frame[i] = (short)( (data[2*i] << 8) | data[2*i+1]);<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face="Courier New"><span
lang=TR style='font-size:10.0pt;font-family:"Courier New";mso-ansi-language:
TR'> }<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=TR style='font-size:10.0pt;mso-ansi-language:TR'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=TR style='font-size:10.0pt;mso-ansi-language:TR'>When my codec application
didn’t work right, I think that the reason is an error at this
convertion. For this aim, I looked at read_samples function in speexenc project
and I can’t understand why the convertion is done in this way:<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=TR style='font-size:10.0pt;mso-ansi-language:TR'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face="Courier New"><span
lang=TR style='font-size:10.0pt;font-family:"Courier New";mso-ansi-language:
TR'> for(i=frame_size*channels-1;i>=0;i--)<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face="Courier New"><span
lang=TR style='font-size:10.0pt;font-family:"Courier New";mso-ansi-language:
TR'> {<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face="Courier New"><span
lang=TR style='font-size:10.0pt;font-family:"Courier New";mso-ansi-language:
TR'>
s[i]=(in[i]<<8)^0x8000;<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face="Courier New"><span
lang=TR style='font-size:10.0pt;font-family:"Courier New";mso-ansi-language:
TR'> }<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face="Courier New"><span
lang=TR style='font-size:10.0pt;font-family:"Courier New";mso-ansi-language:
TR'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=TR style='font-size:10.0pt;mso-ansi-language:TR'>(in my application,
channels is 1 and frame_size=160)<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=TR style='font-size:10.0pt;mso-ansi-language:TR'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=TR style='font-size:10.0pt;mso-ansi-language:TR'>I can understand why
shift left 8, but can’t why we should do XOR operation with 1000 0000
0000 0000. Should I do the convertion operation so and why? Please can you </span></font><span
lang=EN-US style='mso-ansi-language:EN-US'>clarify? Thanks a lot for your
helps.<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=EN-US style='font-size:10.0pt;mso-ansi-language:EN-US'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=EN-US style='font-size:10.0pt;mso-ansi-language:EN-US'>Sincerely<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:65.2pt'><font size=2 face=Arial><span
lang=EN-US style='font-size:10.0pt;mso-ansi-language:EN-US'>Yasemin</span></font><span
lang=TR style='mso-ansi-language:TR'><o:p></o:p></span></p>
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