{
ChangeSignaller<Content> cc1 (this, FFmpegContentProperty::SUBTITLE_STREAMS);
ChangeSignaller<Content> cc2 (this, FFmpegContentProperty::SUBTITLE_STREAM);
job->set_progress_unknown ();
{
ChangeSignaller<Content> cc1 (this, FFmpegContentProperty::SUBTITLE_STREAMS);
ChangeSignaller<Content> cc2 (this, FFmpegContentProperty::SUBTITLE_STREAM);
job->set_progress_unknown ();