Yalantis/uCrop · error · CImgIOException

load_ffmpeg_external(): Failed to open file '%s' with extern

Error message

load_ffmpeg_external(): Failed to open file '%s' with external command 'ffmpeg'.

What it means

load_ffmpeg_external() builds a command line invoking the external ffmpeg binary to decode the video into temporary PPM images. If cimg::system() returns non-zero (ffmpeg missing or it failed to open/decode the input), CImg throws this CImgIOException. It indicates the external ffmpeg invocation failed, not necessarily that the file is absent (that check happened earlier).

Source

Thrown at ucrop/src/main/jni/CImg.h:67472

    **/
    CImgList<T>& load_ffmpeg_external(const char *const filename) {
      if (!filename || !cimg::is_file(filename))
        throw CImgArgumentException(_cimglist_instance
                                    "load_ffmpeg_external(): Specified filename is (null) or does not exist.",
                                    cimglist_instance);
      CImg<charT> command(1024), filename_tmp(256), filename_tmp2(256);
      do {
        cimg_snprintf(filename_tmp,filename_tmp._width,"%s%c%s",
                      cimg::temporary_path(),cimg_file_separator,cimg::filenamerand());
        cimg_snprintf(filename_tmp2,filename_tmp2._width,"%s_000001.ppm",filename_tmp._data);
      } while (cimg::path_exists(filename_tmp2));
      cimg_snprintf(filename_tmp2,filename_tmp2._width,"%s_%%6d.ppm",filename_tmp._data);
      cimg_snprintf(command,command._width,"\"%s\" -v -8 -i \"%s\" \"%s\"",
                    cimg::ffmpeg_path(),
                    CImg<charT>::string(filename)._system_strescape().data(),
                    CImg<charT>::string(filename_tmp2)._system_strescape().data());
      if (cimg::system(command,cimg::ffmpeg_path())!=0)
        throw CImgIOException(_cimglist_instance
                              "load_ffmpeg_external(): Failed to open file '%s' with external command 'ffmpeg'.",
                              cimglist_instance,
                              filename);
      const unsigned int omode = cimg::exception_mode();
      cimg::exception_mode(0);
      assign();
      unsigned int i = 1;
      for (bool stop_flag = false; !stop_flag; ++i) {
        cimg_snprintf(filename_tmp2,filename_tmp2._width,"%s_%.6u.ppm",filename_tmp._data,i);
        CImg<T> img;
        try { img.load_pnm(filename_tmp2); }
        catch (CImgException&) { stop_flag = true; }
        if (img) { img.move_to(*this); std::remove(filename_tmp2); }
      }
      cimg::exception_mode(omode);
      if (is_empty())
        throw CImgIOException(_cimglist_instance
                              "load_ffmpeg_external(): Failed to open file '%s' with external command 'ffmpeg'.",

View on GitHub (pinned to f788b534b4)

Solutions

1. Install ffmpeg or set cimg::ffmpeg_path() to the correct binary location before calling load_video/load_ffmpeg_external.
2. Run the same ffmpeg command manually on the file to see the real decode error (codec, permissions, corruption).
3. Re-encode the video with ffmpeg to H.264/MP4, or use the OpenCV backend (cimg_use_opencv) instead.
4. Verify ffmpeg_path is executable (check version output) from the same process/user context.

Example fix

// before
cimg::ffmpeg_path("/usr/local/bin/ffmpeg"); // binary absent in container
list.load_ffmpeg_external("clip.mp4");

// after
if (cimg::system(CImg<char>::string(cimg::ffmpeg_path()) + " -version") == 0) {
  list.load_ffmpeg_external("clip.mp4");
} else {
  // fall back: re-encode elsewhere or use OpenCV-backed load_video
}

// ensure ffmpeg is present and runnable before attempting load
bool ffmpegAvailable() {
  return cimg::system(
    CImg<char>::string(cimg::ffmpeg_path()) + " -version") == 0;
}

if (!ffmpegAvailable()) { /* use OpenCV backend or fail fast */ }
try {
  list.load_ffmpeg_external(file);
} catch (CImgIOException&) {
  list.load_video(file); // OpenCV backend fallback
}

When it happens

Trigger: cimg::ffmpeg_path() points to a non-existent or non-executable ffmpeg; ffmpeg exits with error because the codec/container is unsupported or the file is corrupt; quoting/escaping issues with exotic filenames.

Common situations: Docker/CI images without ffmpeg installed; ffmpeg version too old for the video codec; PATH set differently inside the app (Android) than in the shell.

Related errors

• save_ffmpeg_external(): Specified filename is (null).
• load_ffmpeg_external(): Specified filename is (null) or does
• load_graphicsmagick_external(): Failed to load file '%s' wit
• load_gzip_external(): Specified filename is (null) or does n
• load_gzip_external(): Failed to load file '%s' with external

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/6bc45580e797ca74. Report an issue: GitHub.