title: Why are subsequent downloads with youtube-dl so much faster?
body: <p>I am downloading and converting multiple YouTube videos to audio only files on my RPi Zero. While the init and first download take quite some time, subsequent downloads are way faster. Is there any way to &quot;warm up&quot; yt-dl to be faster even for the first download? I don't mind any additional initialization time.
  (Changing the order of the URLs has no effect.)</p>
  <pre class="lang-py prettyprint-override"><code>import time
  t1 = time.time()
  
  from youtube_dl import YoutubeDL
  ydl = YoutubeDL({'format': 'bestaudio/best'}) 
  t2 = time.time()
  print(t2 - t1, flush=True)
  
  ydl.download(['https://www.youtube.com/watch?v=xxxxxxxxxxx'])
  t3 = time.time()
  print(t3 - t2, flush=True)
  
  ydl.download(['https://www.youtube.com/watch?v=yyyyyyyyyyy'])
  t4 = time.time()
  print(t4 - t3, flush=True)
  
  ydl.download(['https://www.youtube.com/watch?v=zzzzzzzzzzz',])
  t5 = time.time()
  print(t5 - t4, flush=True)
  </code></pre>
  <p>Output:</p>
  <pre><code>5.889932870864868
  [youtube] xxxxxxxxxxx: Downloading webpage
  [download] 100% of 4.09MiB in 00:01
  15.685529470443726
  [youtube] yyyyyyyyyyy: Downloading webpage
  [download] 100% of 3.58MiB in 00:00
  2.526634693145752
  [youtube] zzzzzzzzzzz: Downloading webpage
  [download] 100% of 3.88MiB in 00:01
  2.4716105461120605
  </code></pre>