evgenij ответил в теме Avidemux: Attempt to open video.mp4 failed!
It's DV video in AVI container. AFAIK Avidemux can't open all kind of DV.
You can try
Avisynth input to Avidemux via AVS Proxy
Changing file extension form AVI to DV allows QuickTime based MPEG Streamclip to open the file (and to cut and convert to MP4). But MPEG Streamclip is not for batch converting files.