Ethereal-dev: RE: [Ethereal-dev] Saving RTP payload!

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From: Miha Jemec <m.jemec@xxxxxxxxxxx>
Date: Tue, 24 May 2005 13:03:16 +0200
When I wrote this part of the code the timing was working. Since then a
lot of code was changed (by others) and I never checked it again. But
the part which does copy this voice into a file is more or less the
same. So I still think that it should work at least if the captured
packets have the correct timing values and that the market bit
information (the bit which indicates the silence surpression phase) is
set correctly.

But of course, also the r_write_silence value can be wrong. I can take a
look if you send me the file, but won't be able to decode it before the
end of the week.

Miha


On Tue, 2005-05-24 at 12:21, Ramamohan Yeggoni wrote:
> Hi Miha,
> 
> Thank you for your response.
> But the problem is that the resulting .au file has the conversation which
> does not start the reverse voice sample in correct timing. It has played
> back as if both parties are keep on talking without listening to each other.
> But there is a
> Clear time difference between forward and reverse voice.
> 
> In static gboolean copy_file(gchar *dest, ...) the following is used to
> write the silence information to one channel.
> 
> 
> 			if (user_data->forward.statinfo.start_time >
> user_data->reversed.statinfo.start_time) {
> 				f_write_silence = (guint32)
> 	
> ((user_data->forward.statinfo.start_time-user_data->reversed.statinfo.start_
> time)*8000);
> 			}
> 			else if (user_data->forward.statinfo.start_time <
> user_data->reversed.statinfo.start_time) {
> 				r_write_silence = (guint32)
> 	
> ((user_data->reversed.statinfo.start_time-user_data->forward.statinfo.start_
> time)*8000);
> 			}
> 
> It seems the r_write_silence value is less than the required. Any thoughts??
> 
> 
> Thanks in advance,
> 
> Regards,
> Ram
> 
> 
> 
> 
> 
> 
> -----Original Message-----
> From: ethereal-dev-bounces@xxxxxxxxxxxx
> [mailto:ethereal-dev-bounces@xxxxxxxxxxxx] 
> Sent: 24 May 2005 10:48
> To: Ethereal development
> Subject: Re: [Ethereal-dev] Saving RTP payload!
> 
> 
> Hi,
> 
> this was the initial idea how to save the rtp payload. In case of "both
> direction" the amplitude of forward and reversed voice samples is simply
> added together and divided by 2. Although the setting inside the .au file
> header is to use stereo mode (channels==1) the actual information is not
> saved seperately. Why? I think there was no need for this that time, since
> this is quite seldom used options. But it can be changed. Look inside
> rtp_analysis.c:
> 
> static gboolean copy_file(gchar *dest, ...)
> 	...	
> 	...
> 	/* both directions */
> 	...
> 	*pd = (unsigned char)linear2ulaw( (f_pd + r_pd)/2 );
> 
> 
> Regards, Miha
> 
> 
> 
> On Tue, 2005-05-24 at 10:54, Ramamohan Yeggoni wrote:
> > Hi All,
> > 
> > Using ethereal, I am trying to save the conversation into single .au 
> > file. We are using g711 a law (8KHz) codec and captured packets using
> > ethereal Version 0.10.10.
> > Saving the rtp payload in forward/reverse directions separately to .au
> > files is fine.
> > When I opt for both directions, the conversation on both channels got
> > overlapped. 
> > While playing back I can hear both channels simultaneously. 
> > Could you please let me know the reason for the same and how to
> > correct this issue.
> > 
> > Any help in this regard is highly appreciated.
> > 
> > Thanks and Regards,
> > Ram
> > 
> > 
> > 
> > 
> > 
> > 
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-- 
Miha Jemec <m.jemec@xxxxxxxxxxx>