CODEWITHSUNDEEP
pythongoffmpegrtsp
J_yang
J_yang

Reputation: 2812

Is there a way to stream RTSP audio stream only to stdout with ffmpeg

I have a webcam that stream the video/audio via rtsp. I wish to make a small program that only detect the audio stream and make a room loudness detection.

My plan is to use ffmpeg to get the audio stream only as a stream of integer/float to stdout. So that I can read the stream in Python or Go as callback and analyse and decibles.

I found an example:

ffmpeg -i rtsp://some_url -c:a aac -c:v copy -hls_list_size 65535 -hls_time 2 "./live.m3u8"

But this write the whole video to files. Any suggestion how to change that?

I am also open to any other solution/packages in other languages that I can do something like

connection = RTSP('rtsp://url')
signal_array = connection.read_audio_frame()

Please advice

Upvotes: 1

Views: 2514

Answers (1)

2e0byo
2e0byo

Reputation: 5954

ffmpeg can be made to output to stdout by adding pipe:. Per the docs:

The accepted syntax is:

pipe:[number]

number is the number corresponding to the file descriptor of the pipe (e.g. 0 for stdin, 1 for stdout, 2 for stderr). If number is not specified, by default the stdout file descriptor will be used for writing, stdin for reading.

http://ffmpeg.org/ffmpeg-all.html#pipe

Personally I would use this in conjunction with a named pipe (FIFO):

mkfifo /tmp/videofifo
ffmpeg -i myfile.mp4 -f avi pipe: > /tmp/videofifo

with open("/tmp/videofifo", "rb") as f:
    ...

Of course, for your use case, you use your ffmpeg command, and you open the fifo in "r" not "rb" mode.

The advantage of using a fifo over just capturing stdout (with subprocess.PIPE directly is probably minimal in your case (ascii data linewise) but seems cleaner in the case of binary data. In any case I prefer to keep the data separate from how I got it. If you do just want to handle stdout directly, use p = subprocess.Popen(cmd, stdout=subprocess.PIPE) and then work on p.stdout, which is a file-like object.

Doubtless there are equivalent ways to launch subprocesses in Go, but to my shame I don't actually know Go at all at the moment.

Upvotes: 2

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