So if you can, please use the second choice explained below:
Because Youtube split audio and video streams for 1080p videos
one need to download them separately and combine them.
1. Download ffmpeg package.Choose static build.
For Win users here is the link:
2. Find your youtube clip and get its address.
3. Go to http://en.savefrom.net/ and download
both audio and video (1080p) streams. For audio use
Audio AAC 256kb/s option if possible.Always use AAC!
Click \/ arrow next to download link to choose
4. Go to ffmpeg folder where ffmpeg is installed,
if it is not added to path environment variable
(For Win version go to .\bin\folder)
5. From there, run ffmpeg using command line below:
ffmpeg -i INPUT_VIDEO_FILENAME -i INPUT_AUDIO_FILENAME
-map 0 -map 1 -c:v copy -c:a copy -shortest OUTPUT_FILE_NAME
(Win users: You can use combineav.bat.
Copy it to ffmpeg binaries folder and run it like:
combineav.bat INPUT_VIDEO_FILENAME INPUT_AUDIO_FILENAME
Output file name is the name of the video filename.)
NOTE: Make sure that you type full path for INPUT_AUDIO_FILENAME
and INPUT_AUDIO_FILENAME files before them !!