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<p class=MsoNormal><span lang=EN-US>Hi,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>This question was initially directed to Russell
but since he advised to use –dev list, I’m going to explain things
first to who unaware.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>The _ast_read of channel.c does post-processing
for DTMF frames. What it does basically is:<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l1 level1 lfo1'><![if !supportLists]><span
lang=EN-US><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=EN-US>Ensures there is a proper gap
between digits<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l1 level1 lfo1'><![if !supportLists]><span
lang=EN-US><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=EN-US>Ensures that every digit has at
least minimal duration<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l1 level1 lfo1'><![if !supportLists]><span
lang=EN-US><span style='mso-list:Ignore'>3.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=EN-US>It emulates DTMF_BEGIN frames to
make proper pair when DTMF_END arrives without preceding DTMF_BEGIN<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Everything would be perfect if AST_FLAG_END_DTMF_ONLY
flag did not exist. The flag indicates that “end user” of _ast_read
is not interested in BEGIN frames. It is used in three situations I’m
aware of:<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l2 level1 lfo3'><![if !supportLists]><span
lang=EN-US><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=EN-US>When Asterisk reads digits (ast_waitfordigit_full)<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l2 level1 lfo3'><![if !supportLists]><span
lang=EN-US><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=EN-US>When channel is being
autoserviced (that happens much more frequently than you could anticipate!). <o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l2 level1 lfo3'><![if !supportLists]><span
lang=EN-US><span style='mso-list:Ignore'>3.<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span lang=EN-US>When channel is bridged to a
channel which does not need BEGIN frames – that is SIP channel with dtmfmode=info<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Since flags may be turned on and off quite
frequently (even when in the middle of emulated digit), it affects the process of
emulation. Things made worse because when autoservice ends, END frames read by
autoservice are feed back into channel queue and participate in the “emulation”
process again when next dequeued by the ast_read. As result, the emulation code
is somewhat cumbersome and prone to errors (as you seen in recent bugs like <a
href="http://bugs.digium.com/view.php?id=11740">http://bugs.digium.com/view.php?id=11740</a>
or <a href="http://bugs.digium.com/view.php?id=11911">http://bugs.digium.com/view.php?id=11911</a>)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>So the QUESTION: why doing this kind of
stuff in the ast_read at all? Most internals of the Asterisk AFAIK do not care
about BEGIN frames nor about digits being properly separated in time. Proper BEGIN/END
pairs may be important for channel drivers – so why not doing DTMF normalization
in the ast_write instead? In ast_write you would not have situations where AST_FLAG_END_DTMF_ONLY
flag changes on the fly and I believe things would be MUCH simpler.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Regards,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Dmitry Andrianov<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
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