YouTube, MP4 and FFMPEG

[Tony Baechler]

If I may say so, the answers you got aren't ideal. I've downloaded many 
videos and they all have sound. I'm blind and I can't comment on the video 
quality. There could be a number of issues here. See more below.

On 2/25/2016 3:53 AM, Amichai Rotman wrote:
> I am trying to use 'youtube-dl' (and other) converters to download a
> specific YouTube video [1]. i want to show it in a lecture and i do not
> trust the availability of an Internet connection over there.

First, are you running the latest version? It's updated about weekly, so if 
it's more than a week or two old, it's probably out of date. Don't rely on 
the package manager. Download it directly from here:

http://yt-dl.org/latest/

Also, run the following command:

youtube-dl --update

> I tried using different methods and managers - but the result is the same -
> an MP4 file without any sound. It seems that after downloading the streams
> separately, FFMPEG is used to join them to an MP4 file. I guess this is the
> failing point...

No, not necessarily. You can pass the --raw option to not use ffmpeg. Trusty 
doesn't ship ffmpeg, it ships libav-tools which in my experience doesn't 
work very well. Add this PPA with this command with sudo or as root:

add-apt-repository ppa:mc3man/trusty-media

Of course run "apt-get update" to update the cache. Then, purge libav-tools 
and install ffmpeg instead. That should solve your problem. If not, what do 
you get with the --raw switch? Another possibility is you aren't allowed to 
view the video in the geographic location of the server, but you say it 
works on Windows, so that's unlikely.

> Just to make sure, I asked a friend of mine to ty it on Windows and it
> worked for him. He said he hears the sound, but when i try to play it on my
> Ubuntu 14.04 machines - *no sound!*


What is the output of file and ffprobe on the mp4 file? Is it really a .mkv 
file with an .mp4 extension? What is you pass the "--format bestaudio" 
option to youtube-dl?