Demo RuntimeError: function signature mismatch

Describe the bug
Throws error when trying to add "-preset", "veryfast"
worker.js onmessage() captured an uncaught exception: RuntimeError: function signature mismatch

To Reproduce
Using your demo section at https://ffmpegwasm.github.io/#demo
use the following arguments, and the error should be reproducible.

{
  args: ['-i', 'video.avi', "-preset", "veryfast", '-c:v', 'libx264', 'video.mp4'],
  inFilename: 'video.avi',
  outFilename: 'video.mp4',
  mediaType: 'video/mp4',
}

Expected behavior
Should just encode the file. Tested on ffmpeg locally via CLI and arguments are valid.

Screenshots
https://i.imgur.com/UVFTbLU.png

Desktop (please complete the following information):

OS: [Windows 10 2004]
Browser [Chrome]
Version [87.0.4280.66]

Additional context
Just as a note, encoding is very very slow. Is this normal?

Hmm, can you provide your video file for me to test?
And yes, it is normal that it is slow. Lol

Here is a quick video of Minecraft.
Test Video.zip

With these arguments ['-i', 'video.avi', "-preset", "veryfast", '-c:v', 'libx264', 'video.mp4'] it crashes. Let me know if you can reproduce this with the given video file.

Note, if I change veryfast to fast it works. Hope that helps

Hi,
Faced with a similar issue, after I updated @ffmpeg/ffmpeg from 0.8.3 to 0.9.6.

Command that create a video from images (in 0.8.3 API was different, I keep the latest API for example)

ffmpeg.run(
      `-framerate`, `${videoOptions.fps}`,
      `-pattern_type`, `glob`,
      `-i`, `*.jpeg`,
      `-c:v`, `libx264` ,
      `-preset`, `veryfast`,
      `-crf`, `17`,
      `out.mp4`,
    );

It throwns exeption Uncaught RuntimeError: function signature mismatch.

If I change veryfast to fast/superfast/ultrafast, it works well.

OS: [macOs Mojave 10.14.6]
Browser [Chrome]
Version [87.0.4280.88]

Is this issue abandoned? I am having the same problem, namely that using the veryfast preset gives a "signature mismatch" error, while other fast presets work just fine

Fix crash-level bugs: stack leak, MT deadlock/OOM, x264 threads, x265…

Navigation Menu

Repository navigation

Demo RuntimeError: function signature mismatch #116

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Demo RuntimeError: function signature mismatch #116

Description

Activity

jeromewu commented on Nov 19, 2020

EladKarni commented on Nov 20, 2020

katmai7 commented on Jan 7, 2021

Fran314 commented on Sep 18, 2025

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions