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I am wondering, how much the speed gain is, when using multiple threads (16), because there is more than just writing frames out simultaneously? Can someone give some information?

thanks

  • I don't know about this specific library, but some tests around the web compare h264 encoding with and without hyperthreading (simplified: twice the threads with more or less half the performance) and it's usually a wash. That means it's pretty close to 2x threads = 2x performance. Things might get more complicated if you want to do realtime encoding. – Peter Sep 11 '14 at 11:14
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x264 scales pretty linearly. So doubling the thread will double the FPS ( give or take a few percent due to memory speed CPU cache size and locks). But it may increase the final file size (very) slightly. Especially if you use slice based threading.

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  • As i read per default, it uses just one thread, so would i have 16 times speed gain, when i up it to 16? – user1767754 Sep 11 '14 at 17:32
  • You may start loosing efficiency after 8 or so, but it really depends on your CPU, RAM speed, other x264 options, etc. – szatmary Sep 11 '14 at 17:36

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