README.md with deps, build, usage, troubleshooting

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

-**APM Quality Assessment tool**
+# APM Quality Assessment tool
 
-Python wrapper of audioproc_f with which quality assessment can be automatized.
-The tool allows to simulate different noise conditions, input signals, APM
-configurations and it computes different scores.
+Python wrapper of `audioproc_f` with which quality assessment can be
+automatized. The tool allows to simulate different noise conditions, input
+signals, APM configurations and it computes different scores.
 Once the scores are computed, the results can be easily exported to an HTML page
 which allows to listen to the APM input and output signals and also the
 reference one used for evaluation.
 
-IMPORTANT: **the whole code has not been landed yet.**
+## Dependencies
+
+ - OS: Linux
+ - Python 2.7
+ - Python libraries: numpy, scipy, pydub (0.17.0+)
+   - `$ sudo apt install python-numpy python-scipy`
+   - `$ sudo pip install pydub`
+ - PolqaOem64 (see http://www.polqa.info/)
+    - Tested with POLQA Library v1.180 / P863 v2.400
+ - Aachen Impulse Response (AIR) Database
+    - Download https://www2.iks.rwth-aachen.de/air/air_database_release_1_4.zip
+ - Input probing signals and noise tracks (you can make your own dataset - *1)
+
+## Build
+
+ - Compile WebRTC
+ - Go to `out/Default/py_quality_assessment` and check that
+   `apm_quality_assessment.py` exists
+
+## First time setup
+
+ - Deploy PolqaOem64 and set the `POLQA_PATH` environment variable
+   - e.g., `$ export POLQA_PATH=/var/opt/PolqaOem64`
+ - Deploy the AIR Database and set the `AECHEN_IR_DATABASE_PATH` environment
+ variable
+   - e.g., `$ export AECHEN_IR_DATABASE_PATH=/var/opt/AIR_1_4`
+ - Deploy probing signal tracks into
+   - `out/Default/py_quality_assessment/probing_signals` (*1)
+ - Deploy noise tracks into
+   - `out/Default/py_quality_assessment/noise_tracks` (*1, *2)
+
+(*1) You can use custom files as long as they are mono tracks sampled at 48kHz
+     encoded in the 16 bit signed format (it is recommended that the tracks are
+     converted and exported with Audacity).
+
+(*2) Adapt `EnvironmentalNoiseGenerator._NOISE_TRACKS` accordingly in
+     `out/Default/py_quality_assessment/quality_assessment/noise_generation.py`.
+
+## Usage (scores computation)
+
+ - Go to `out/Default/py_quality_assessment`
+ - Check the `apm_quality_assessment.sh` as an example script to parallelize the
+   experiments
+ - Adjust the script according to your preferences (e.g., output path)
+ - Run `apm_quality_assessment.sh`
+ - The script will end by opening the browser and showing ALL the computed
+   scores
+
+## Usage (export reports)
+
+Showing all the results at once can be confusing. You therefore may want to
+export separate reports. In this case, you can use the
+`apm_quality_assessment_export.py` script as follows:
+
+ - Set --output_dir to the same value used in `apm_quality_assessment.sh`
+ - Use regular expressions to select/filter out scores by
+    - APM configurations: `--config_names, -c`
+    - probing signals: `--input_names, -i`
+    - noise generators: `--noise_generators, -n`
+    - scores: `--eval_scores, -e`
+ - Assign a suffix to the report name using `-f <suffix>`
+
+For instance:
+
+```
+$ ./apm_quality_assessment-export.py \
+  -o ~/data/apm_quality_assessment \
+  -e \(polqa\) \
+  -n \(echo\) \
+  -c "(^default$)|(.*AE.*)" \
+  -f echo
+```
+
+## Troubleshooting
+
+The input wav file must be:
+  - sampled at a sample rate that is a multiple of 100 (required by POLQA)
+  - in the 16 bit format (required by `audioproc_f`)
+  -  encoded in the Microsoft WAV signed 16 bit PCM format (Audacity default
+     when exporting)
+
+Depending on the license, the POLQA tool may take “breaks” as a way to limit the
+throughput. When this happens, the APM Quality Assessment tool is slowed down.
+For more details about this limitation, check Section 10.9.1 in the POLQA manual
+v.1.18.
+
+In case of issues with the POLQA score computation, check
+`py_quality_assessment/eval_scores.py` and adapt
+`PolqaScore._parse_output_file()`.
+The code can be also fixed directly into the build directory (namely,
+`out/Default/py_quality_assessment/eval_scores.py`).