<div dir="ltr">Seriously cool Lee, I always wondered about this myself :) Thanks for taking the time to post this.</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Jul 23, 2013 at 5:36 PM, Lee Azzarello <span dir="ltr"><<a href="mailto:lee@guardianproject.info" target="_blank">lee@guardianproject.info</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I recorded the sound with a microphone. It was coming out of my<br>
Android device running a debug build of Linphone. I can describe the<br>
process to reproduce it.<br>
<br>
But now...for the TWIST!<br>
<br>
There was no human speech happening when I made this recording. No<br>
vowels, no consonants, no phrases. The only sound in the room was a<br>
fan...producing noise (though from the angle of my desk, unlikely<br>
white noise).<br>
<br>
There's a chance the sound was not what I thought. Perhaps it was a<br>
codec error, though it didn't sound like a looping buffer. I kept it<br>
on for over a minute. Wireshark has a bunch of VoIP protocol<br>
analyzers, including a utility that will try and recover an audio file<br>
from captured RTP packets. That'll be an interesting comparison.<br>
<br>
-lee<br>
<div><div class="h5"><br>
On Tue, Jul 23, 2013 at 5:20 PM, Hans-Christoph Steiner<br>
<<a href="mailto:hans@guardianproject.info">hans@guardianproject.info</a>> wrote:<br>
><br>
> I could also see adaptive audio filters that fill in the vowel sounds based on<br>
> the same kind of algorithm as auto-complete typing. It could use the timing<br>
> and spectrum of the audio events as one source of information for filling in<br>
> the rest. A decent DSP math person spending a few months on that problem<br>
> could make some noticeable improvements. That bar is not very high.<br>
><br>
> Lee, where is that sound file from? Its pretty awesome.<br>
><br>
> .hc<br>
><br>
> On 07/23/2013 04:57 PM, Josh Steiner wrote:<br>
>> Whoa, that is way too recognizably human for comfort. i could totally see<br>
>> with some training being able to understand that.<br>
>><br>
>> -j<br>
>><br>
>><br>
>> On Tue, Jul 23, 2013 at 1:47 PM, Lee Azzarello <<a href="mailto:lee@guardianproject.info">lee@guardianproject.info</a>>wrote:<br>
>><br>
>>> Hello all,<br>
>>><br>
>>> There have been some conversations recently on IRC and on the web<br>
>>> about VBR audio codecs and plaintext recovery.<br>
>>><br>
>>> It's an interesting conversation and one which will change a lot in<br>
>>> our times. While I was testing some video call clients, I saw a bug<br>
>>> between a custom build of Linphone on Android and a nightly of Jitsi<br>
>>> on OS X where Linphone tried to play back the encrypted audio through<br>
>>> the speaker without first decrypting it.<br>
>>><br>
>>> This is what a SRTP audio stream sounds like to a wiretap. The codec<br>
>>> is speex at 16 kHZ, I believe it is VBR but I'm not certain.<br>
>>><br>
>>> <a href="http://ge.tt/9FG7Tem/v/0?c" target="_blank">http://ge.tt/9FG7Tem/v/0?c</a><br>
>>><br>
>>> -lee<br>
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