Pitahaya
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Live streaming audio
You can use Pitahaya to stream high quality audio in real time over a video channel. The video will appear silent to anyone not decoding the stream.
Encoding
Requires: ffmpeg and node.js.
If running windows, install cygwin to run the commands on this page.
The following command will take the file audio.flac and live stream it to YouTube as a 128 kbps MP3 over the video channel. Be sure to replace the string abcd-efgh-ijkl-mnop-qrst with your youtube live streaming key found on your live dashboard page.   
ffmpeg -nostats -loglevel 0 \
-re -i audio.flac \
-f s16le -acodec pcm_s16le -ar 44100 -ac 2 - \
| ffmpeg -nostats -loglevel 0 \
-f s16le -ar 44100 -ac 2 -i - \
-acodec libmp3lame -b:a 128k -f mp3 - \
| pitahaya --tx mp3 \
| ffmpeg -f lavfi \
-i anullsrc=channel_layout=stereo:sample_rate=11025 \
-framerate 8 -f rawvideo \
-pixel_format rgba -video_size 640x360 \
-i - -shortest -c:v libx264 \
-crf 32 -pix_fmt yuv420p -preset slow \
-r 8 -g 16 -f flv \
"rtmp://a.rtmp.youtube.com/live2/abcd-efgh-ijkl-mnop-qrst"
After running the command, wait a moment and you will see the stream start to be received on the live dashboard page. It might give you a warning that the stream quality has an 'unsupported resolution' but you can ignore this warning.  It is probably best to set the stream latency to 'normal latency' on the live dashboard page to ensure the highest possible quality stream.

Alternatively, if you want to live stream audio from audio playing on your desktop computer, rather than from a file, you can find the command to do that here.

Note that you can stream to different servers, e.g. Twitch, by replacing the rtmp url on the last line, e.g. "rtmp://hou.contribute.live-video.net/app/TWITCHSTREAMKEY"

Decoding in the browser Pitahaya encoded audio can be decoded and played back in the browser using the bookmarklet.
Decoding via command line
Requires: ffmpeg, node.js, and streamlink.
Decode audio with the following command: (replace abcdefghijk with a valid youtube url path) 
streamlink --quiet \
https://youtu.be/abcdefghijk 360p -o - \
| ffmpeg -nostats -loglevel 0 \
-i - -vcodec rawvideo \
-pix_fmt rgba \
-r 16 -f rawvideo - \
| pitahaya --rx 360p \
| ffplay -nostats -loglevel 0 -
Encryption If you want to password protect the audio transmission, add a passphrase via pitahaya --tx mp3 somepassphrase when encoding or pitahaya --rx 360p somepassphrase when decoding. You can also type the passphrase in the bookmarklet's input field if you want to decrypt the audio in the browser.