There's a video I need to view, foreign language film. I was checking it with ffmpeg, and it seemed legitimate except the third stream was something I've never seen before. I want to know what it is and how to view the stream's contents.

I tried dumping it with

ffmpeg -dump_attachment:t:0 subs.txt -i input.mp4

Yet the file that was dumped is invisible...but showed up a number in the file folder. I'm using windows 8.1 and hidden folders/files are set to visible. Maybe my command is wrong and this is a subfile... instead of a information file..(i tried s:0 instead but no difference)? Or I can't dump this? Should I change from .txt to some other extension or what do I need to do to dump and view it?

I just don't know what it is, and i want to know what it is. If we assume it's a subfile, I should be able to open it in a text editor right? So how can I do that...preferably a safe way of doing so.

enter image description here

1 Answer 1


The 3rd stream in your input is a regular stream. Attachments are basically extradata attached to streams.

You would use

ffmpeg -i input.mp4 -map 0:2 -c copy -f data subs.txt
  • That created a blank .txt file. I can't get any subtitles to showup in vlc player either, it recognizes the stream tho, so maybe its supposed to be a blank file. What does the "-f data" do? I thought -f had something to do with generating raw data, not sure what "data" does though.
    – kite
    Dec 3, 2019 at 0:38
  • 1
    data muxer is for any data (binary/text) to be dumped while avoiding all automatic processing that ffmpeg may perform for streams identified as a video or audio type.
    – Gyan
    Dec 3, 2019 at 4:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.