CODEWITHSUNDEEP
node.jsffmpeg
keenan
keenan

Reputation: 13

How to capture a log message coming out of node JS spawn ffmpeg command

I am trying to find the silent parts of an audio recording. This command does exactly what I want on my local machine.

ffmpeg -i http://twf-audio.s3.amazonaws.com/uploads/DBC50460-9A5C-4174-9885-07337A582D58_1377839443598_tell.m4a -af silencedetect=n=-40dB:d=0.2 -f null -

It sends a bunch of messages to the command line including these last three which are the lines of data that I need. (for reference: ffmpeg silencedetect docs)

[silencedetect @ 0x7feea040cf20] silence_start: 0.0321995

[silencedetect @ 0x7feea040cf20] silence_end: 0.975238 | silence_duration: 0.943039

[silencedetect @ 0x7feea040cf20] silence_start: 1.47184

I cannot figure out how to get that message out. Here is the nodejs code that is running. The only event that is triggered is the 'exit'. I thought that "pipe:1" sends output to stdout but that does not do anything.

var ffmpeg = spawn('ffmpeg', ['-i',filename,'-af','silencedetect=n=-40dB:d=0.2', '-f', 'null','-y', 'pipe:1' ]);

ffmpeg.on('message', function(data) {
    console.log('ffmpeg2 PARENT got message:', JSON.stringify(data));
});

ffmpeg.stdout.on('data', function(data) {
    console.log('ffmpeg stdout data = '+JSON.stringify(data) );
});

ffmpeg.on('exit', function (code, signal) {
  console.log('child process exited with code:' + code + ' signal:' + signal);
});

Upvotes: 1

Views: 2621

Answers (1)

hvrauhal
hvrauhal

Reputation: 432

The pipe:1 argument to ffmpeg sends the transcoded data stdout.

The output that's shown when you run the command outside of node is sent to stderr by default, and you can handle it in your program with:

ffmpeg.stderr.on('data', function(data) {
  console.log('ffmpeg stderr data = '+data );
});

Upvotes: 2

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