How to write ROS AudioData message into wav file?

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I'm using ReSpeaker Mic Array v2.0 on my robot, I used the following git repo: https://github.com/furushchev/respeaker_ros.git to capture the audio received by the speaker. I subscribed to it's raw audio ros topic /audio which is just byte array data(http://docs.ros.org/noetic/api/audio_common_msgs/html/msg/AudioData.html)

How can I write the AudioData message's uint8[] data into a wav file in C++? I would like to play the wav file by other means afterwards.

I saw that in ros audio_common library example it uses gstreamer to do the writing, but I'm quite confused after reading the code(https://github.com/ros-drivers/audio_common/blob/master/audio_capture/src/audio_capture.cpp)

ros wav gstreamer audio c++
1 Answers

Example that you saw is using Gstremaer's alsasrc to capture audio from mic in this line

_source = gst_element_factory_make("alsasrc", "source");

So Gstreamer's pipeline is internally handling/capturing audio byte array and, in case of input parameters dst_type=="filesink" and format=="wave", encoding it with

_filter = gst_element_factory_make("wavenc", "filter");

and creating .wav file with

_sink = gst_element_factory_make("filesink", "sink");

On the other hand, running that code with input parameters dst_type=="appsink" and format=="wave" actually captures audio bytes again but, instead of writing to file, publishes them on ros topic /audio.

If you cannot (from any reason) use this code with input parameters dst_type=="filesink" and format=="wave", I suppose you will need to use Gstreamer's appsrc element and feed it with bytes from your AudioData message. In that case, the rest of Gstreamer pipeline for encoding and writing to file should remain the same as in the example.

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