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• Révision 22126 : Report minimal de r22116 r22118 r22119 : #3418 : Octave utilise une configuration...

  10 mai 2015, par cedric -

• How to convert a Buffer to a video with fluent-ffmpeg and write the output to a WritableStream

  30 octobre 2023, par isaac.g

  For some context, I need to quickly render a small video (6.5 seconds long, at 15 FPS), and send it in a Discord channel with discord.js. I don't want to ever have to write anything to disk, because that'll slow it down and I just don't need it downloaded. So far, I was able to write the video to disk, but now I want to skip that step and send the video Buffer straight to discord.js. I was also able to output the video from ffmpeg to Discord as an audio file, but when I try to use the .mp4 format, I get a "Conversion failed !" error.

  


  I rendered the individual frames for the video using the canvas module, and export all of them as pngs using canvas.toBuffer("image/png");, and then push all the frames to an array. Then I combine the frames to one Buffer using Buffer.concat(), and then create a ReadableStream from the nodejs stream module. I also needed to write a custom WritableStream class that implements the _write method. Here's the class :

  


  class MyWritable extends Stream.Writable {
    constructor() {
        super();
        this.buffer = Buffer.from([]);
    }

    _write(chunk, encoding, callback) {
        this.buffer = Buffer.concat([this.buffer, chunk]);
        callback();
    }
}


  


  And here's how I implement everything using fluent-ffmpeg :

  


  const allFrames = Buffer.concat(framesArray);
const readable = Stream.Readable.from(allFrames);
const writable = new MyWritable();

const output = await (new Promise((resolve, reject) => {
    ffmpeg()
        .input(readableStream)
        .inputOptions([
            `-framerate 15`,
        ])
        .input("path_to_audio_file.mp3")
        .videoCodec("libx264")
        .format("mp4")
        .outputOptions([
            "-pix_fmt yuv420p"
        ])
        .duration(6.5)
        .fps(15)
        .writeToStream(writable)
        .on("finish", () => {
            // this is never reached, but it should resolve the promise with all the data that was written to the WritableStream (which should be the video)
            resolve(writable.buffer);
        })
        .on("error", (err) => {
            // this is never reached also
            reject(err);
        })
}))

// then I try to send the output buffer to Discord as an attachment, but I don't ever get here anyway


  


  And here's the error I get :

  


  node:events:491&#xA;      throw er; // Unhandled &#x27;error&#x27; event&#xA;      ^&#xA;&#xA;Error: ffmpeg exited with code 1: Conversion failed!&#xA;&#xA;    at ChildProcess.<anonymous> (/Users/isaac/Documents/Github/DiscordBot/node_modules/fluent-ffmpeg/lib/processor.js:182:22)&#xA;    at ChildProcess.emit (node:events:513:28)&#xA;    at ChildProcess._handle.onexit (node:internal/child_process:293:12)&#xA;Emitted &#x27;error&#x27; event on FfmpegCommand instance at:&#xA;    at emitEnd (/Users/isaac/Documents/Github/DiscordBot/node_modules/fluent-ffmpeg/lib/processor.js:424:16)&#xA;    at endCB (/Users/isaac/Documents/Github/DiscordBot/node_modules/fluent-ffmpeg/lib/processor.js:544:13)&#xA;    at handleExit (/Users/isaac/Documents/Github/DiscordBot/node_modules/fluent-ffmpeg/lib/processor.js:170:11)&#xA;    at ChildProcess.<anonymous> (/Users/isaac/Documents/Github/DiscordBot/node_modules/fluent-ffmpeg/lib/processor.js:182:11)&#xA;    at ChildProcess.emit (node:events:513:28)&#xA;    at ChildProcess._handle.onexit (node:internal/child_process:293:12)&#xA;</anonymous></anonymous>

  


  Like I said earlier, if I change the format to an audio format, it exports perfectly fine. But I have no idea where the problem is with converting to a video.
Thanks in advance.

  


• Convert from webm to gif using FFMPEG with minimal loss in quality

  27 novembre 2017, par Neo Herakles

  so I want to convert all my webm files to gif but the quality degraded incredibly, there’s some barely visible lines along the picture, tried using crf to improve it but it doesn’t, could you help me ? Here’s my code :

  @echo off
  
  setlocal
  
  for %%G in ("%~dp0\webm\*.webm") do (
  
      ffmpeg -i "%%G" -pix_fmt rgb24 -crf 17 "%%G.gif"
  
      )
  
  )
  
  endlocal
  
  pause

  Also, could you instruct me in a way in which I can remove the .webm from the output filename ? it outputs as "(file name).webm.gif"