Download and combine DASH audio/video concurrently for streaming

[RunasSudo]

Please follow the guide below

• You will be asked some questions and requested to provide some information, please read them carefully and answer honestly
• Put an x into all the boxes [ ] relevant to your issue (like that [x])
• Use Preview tab to see how your issue will actually look like

---

Make sure you are using the latest version: run youtube-dl --version and ensure your version is 2016.11.18. If it's not read this FAQ entry and update. Issues with outdated version will be rejected.

• I've verified and I assure that I'm running youtube-dl 2016.11.18

Before submitting an issue make sure you have:

• At least skimmed through README and most notably FAQ and BUGS sections
• Searched the bugtracker for similar issues including closed ones

What is the purpose of your issue?

• Bug report (encountered problems with youtube-dl)
• Site support request (request for adding support for a new site)
• Feature request (request for a new functionality)
• Question
• Other

---

With non-DASH Youtube streams, the partially-downloaded file can be watched in a suitable player like VLC as the video downloads. As DASH streams are sent and downloaded as separate audio and video streams, this does not appear to be possible with youtube-dl alone at this stage, hence one must inconveniently wait until both video and audio streams have completely downloaded to watch the video.

This can be achieved using ffmpeg and separate invocations of youtube-dl, for example:

ffmpeg -i <(youtube-dl -f 135 $URL -o -) -i <(youtube-dl -f 140 $URL -o -) -c copy out.mkv

However this approach lacks the ease user-friendliness of a youtube-dl parameter, and is also not particularly robust (for example, my test video plays only in ffplay, not vlc).

It would be wonderful if youtube-dl had the capacity to download DASH audio/video streams and combine them into an output file concurrently, to allow watching a video as it downloads.