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• Dynamically record parts of a video stream using ffmpeg based on incoming events

  12 septembre 2023, par ganjim

  Say I have a RTSP stream running on some server.

  


  I want to record parts of this video stream based on some events that will come up on my machine.
My goal is to record 10 seconds before up to 10 seconds after the PTS in any received event. Consider that I have a way to synchronize the PTS between the sender and the receiver, but by the time I receive the events, its already streamed and is in the past.
So I either need to have the ffmpeg command running already, or to have buffered streaming video in my memory.

  


  I just added some code with comments as a way to simulate the situation, it is not complete as I still don't have a working solution. But I'm looking to understand if ffmpeg has capabilities for dealing with rtsp streams suitable for this situation.

  


  const { spawn } = require('child_process');

function processEvent(event){
  
  let startTime = event.pts - 10
  let endTime = event.pts + 10

  const ffmpegArgs = [
    '-i', "rtspUrl",
    '-ss', startTime.toString(),
    '-to', endTime.toString(),
    '-c', 'copy',
    '-f', 'mp4',
    `output_${startTime}_${endTime}.mp4` // Output filename
  ];
  // Here it is obviously not possible to give ffmpeg a negative startTime.
  // We either have to have spawned the ffmpeg command and somehow give it a starting time for recording on demand or have a buffering system in place.
  // Having a buffer to store every raw frame and then attach them after endTime is also considerably CPU and memory intensive.
  // Looking for alternative ways to achieve the same output.

  const ffmpegProcess = spawn('ffmpeg', ffmpegArgs, {
    stdio: 'inherit'
  });
}

// Code to simulate the events:
// imagine these pts to be relative to Date.now(), so using negative PTS to show the events are going to be in the past by the time we receive them.
setTimeout(() => {
  const event1= { pts: -30 };
  processEvent(event1);
}, 1000);

setTimeout(() => {
  const event2 = { pts: -20 };
  processEvent(event2);
}, 5000);


  


• ffmepg record multi source audio

  11 août 2015, par 雨夜风声

  I have a task to use ffmpeg sdk avdevice to make a function to record screen and audio into one video file. Now i have make it support record screen and the audio from the default microphone.

  However, now I have to change the code to support two microphone not just the default microphone.

  I have no idea. Would please give me some advice, thanks

• FFMPEG Error WaveHeader : only supports bitsPerSample 8 or 16

  20 mars 2014, par fsi

  From this link, I'm having the same problem, but it might be on the converter using ffmpeg, converting amr to wav file.

  ffmpeg -i input.amr -acodec pcm_s16le -ac 1 -ar 48000 -ab 768k output.wav;

  But when I'm comparing this file and another wav file, give me the error. I'm missing something ?