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• Spawned ffmpeg process in nodejs Transform stream with flow control doesn't process input stream

  30 septembre 2022, par user1832894

  I have implemented a node.js Transform stream class that spawns ffmpeg and streams out the transformed stream at a controlled realtime rate. Below is my _transform() method.

  


  this.rcvd += chunk.length
console.log('received bytes %d', this.rcvd)
const ready = this.ffmpeg.stdin.write(chunk, encoding, err => err
  ? cb(err)
  : ready
    ? cb
    : this.ffmpeg.stdin.once('drain', cb))


  


  I want to write to ffmpeg's stdin stream till it returns false, at which point I wait for the drain event to write more data.

  


  Concurrently, I have a timer that fires every 40 milliseconds that reads ffmpeg's stdout and pushes it to the Transform stream's output (the readable side). Code not complete, but the folllowing describes it well.

  


  const now = Date.now()
const bytesToTransmit = (now - this.lastTx) * 32

const buf = this.ffmpeg.stdout.read()

if (buf == null) return

if (buf.length <= bytesToTransmit) {
  this.push(buf)
  this.lastTx += buf.length * 32
  return
}

this.push(buf.slice(0, bytesToTransmit))
this.lastTx = now

// todo(handle pending buffer)
this.pending = buf.slice(bytesToTransmit)


  


  The issue I am facing is that the first write (of 65k bytes) returns false, and after that I never receive the drain event. FFMpeg doesn't start processing the data until certain amount of data (256k bytes in my case) has been written, and once I start waiting for the drain event, I never recover control.

  


  I've tried a few ffmpeg options like nobuffer but to no avail. What am I doing wrong ? Any ideas would be super helpful.

  


  Thanks !

  


• Merge pull request #253 from zeroclipboard/origins-array-bug

  17 octobre 2013, par jonrohan

  Merge pull request #253 from zeroclipboard/origins-array-bug
  Array.push returns a number, not an array.
  

• FFmpeg stucks for few seconds on start

  7 février 2018, par tarasmorskyi

  I’m trying to cut and resize video on Android(but it is similar on MacOS) , but when I run the ffmpeg command it returns me

  frame= 0 fps=0.0 q=0.0 size= 0kB time=00:00:00.00 bitrate=N/A speed=

  It repeats for about 20 sec (I have 4K video with 3 sec duration).

  Is there any way to improve process speed ? Here is example of my ffmpeg command

  ffmpeg -y -i input.mp4 -ss 00:01.82 -to 00:02.94 -vf scale=500:1024 -c:v libx264 -c:a aac -b:v 500k -b:a 96k output.mp4