The best quality audio and video from this Youtube video

youtube-dl

I would like to download a youtube video with the best video quality and audio quality.
Based on this answer, I would like to pick the best video and best audio, then merge them together.
However, I'm unsure which one will be the best choice.
The -F command gave me the following information

249          webm       audio only DASH audio   54k , opus @ 50k, 8.60MiB
250          webm       audio only DASH audio   68k , opus @ 70k, 10.98MiB
171          webm       audio only DASH audio  123k , vorbis@128k, 19.82MiB
140          m4a        audio only DASH audio  131k , m4a_dash container, mp4a.40.2@128k, 23.65MiB
251          webm       audio only DASH audio  132k , opus @160k, 21.46MiB
160          mp4        256x144    144p  110k , avc1.4d400c, 30fps, video only, 6.48MiB
278          webm       256x144    144p  119k , webm container, vp9, 30fps, video only, 15.64MiB
242          webm       426x240    240p  219k , vp9, 30fps, video only, 16.57MiB
133          mp4        426x240    240p  275k , avc1.4d4015, 30fps, video only, 14.96MiB
243          webm       640x360    360p  409k , vp9, 30fps, video only, 25.87MiB
134          mp4        640x360    360p  520k , avc1.4d401e, 30fps, video only, 26.78MiB
244          webm       854x480    480p  749k , vp9, 30fps, video only, 37.32MiB
135          mp4        854x480    480p  975k , avc1.4d401f, 30fps, video only, 38.80MiB
136          mp4        1280x720   720p 1343k , avc1.4d401f, 30fps, video only, 52.98MiB
247          webm       1280x720   720p 1509k , vp9, 30fps, video only, 65.66MiB
17           3gp        176x144    small , mp4v.20.3, mp4a.40.2@ 24k, 13.90MiB
36           3gp        320x180    small , mp4v.20.3, mp4a.40.2, 41.49MiB
18           mp4        640x360    medium , avc1.42001E, mp4a.40.2@ 96k, 68.85MiB
43           webm       640x360    medium , vp8.0, vorbis@128k, 96.53MiB
22           mp4        1280x720   hd720 , avc1.64001F, mp4a.40.2@192k (best)

I assume
247 = best video available. However, I'm not sure what 1509k mean?
After selecting this, Mediainfo told me that the video has 477kb/s. Was I doing something wrong?

Best Answer

Please read the youtube-dl documentation:

By default youtube-dl tries to download the best available quality, i.e. if you want the best quality you don't need to pass any special options, youtube-dl will guess it for you by default.

Note that if you have a specific requirement regarding video and audio codecs or formats used, you should set the format:

You can also use a file extension (currently 3gp, aac, flv, m4a, mp3, mp4, ogg, wav, webm are supported) to download the best quality format of a particular file extension served as a single file, e.g. -f webm will download the best quality format with the webm extension served as a single file

YouTube will offer VP9-encoded video and Opus-encoded audio when querying a WebM format; these are the itags starting with a "2". As these are way more efficient (i.e., offer better quality at the same size) than the H.264- and AAC-encoded video and audio streams starting with "1", you could choose -f webm for any download.

Also, there are more options for querying the format.

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