Conversational Speech generator tool

webrtc/modules/audio_processing/test/py_conversational_speech/README.md

Index: webrtc/modules/audio_processing/test/py_conversational_speech/README.md
diff --git a/webrtc/modules/audio_processing/test/py_conversational_speech/README.md b/webrtc/modules/audio_processing/test/py_conversational_speech/README.md
new file mode 100644
index 0000000000000000000000000000000000000000..9abd275250acac7cb725938af0375696975c8004
--- /dev/null
+++ b/webrtc/modules/audio_processing/test/py_conversational_speech/README.md
@@ -0,0 +1,60 @@
+#Conversational Speech generator tool
+
+Python tool to generate two-ends audio track pairs to simulate conversational
+speech.
+
+The input to the tool is a directory containing a number of audio tracks and
+a text file indicating how to time the sequence of speech turns (see the Example
+section).
+
+Since the timing of the speaking turns is specified by the user, the generated
+tracks may not be suitable for testing scenarios in which there is unpredictable
+network delay (e.g., end-to-end RTC assessment).
+Instead, the generated pairs can be used when the delay is constant (obviously
+including the case in which there is no delay).
+For instance, echo cancellation in the APM module can be evaluated using the
+generated tracks as input and reverse input.
+
+By indicating negative and positive time offsets, one can reproduce cross-talk
+and silence in the conversation.
+
+IMPORTANT: **the whole code has not been landed yet.**
+
+###Example
+
+For each end, there is a set of audio tracks, e.g., a1, a2 and a3 (speaker A)
+and b1, b2 (speaker B).
+The text file with the timing information may look like this:
+```  a1 0

[hlundin-webrtc, 2017/03/03 14:01:10]

Is this implicit assumption that the speakers switch after each file? That is,
it is not possible to pass two files in a row to A, and then one file to B,
right?

If so, please, document this.

[AleBzk, 2017/03/03 15:27:08]

Good point. I think it's easier to allow freedom here (also in terms of coding).
This requires to add a third column to the text file to indicate which end is
active. This is also good to make an arbitrary number of ends (not just two).

+  b1 0
+  a2 100
+  b2 -200
+  a3 0```
+The first column contains the audio track file names, the second the offsets (in
+milliseconds) used to concatenate the chunks.
+
+Assume that all the audio tracks in the example above are 1000 ms long.
+The tool will then generate two tracks that look like this:
+
+```Track A:
+  a1 (1000 ms)
+  silence (1100 ms)
+  a2 (1000 ms)
+  silence (800 ms)
+  a3 (1000 ms)```
+
+```Track B:
+  silence (1000 ms)
+  b1 (1000 ms)
+  silence (900 ms)
+  b2 (1000 ms)
+  silence (1000 ms)```
+
+The two tracks can be also visualized as follows (one characheter represents
+100 ms, "." is silence and "*" is speech).
+
+```t: 0         1        2        3        4        5 (s)
+A: **********...........**********........**********
+B: ..........**********.........**********..........```
+                                ^ 200 ms cross-talk
+        100 ms silence ^