As there is little movement in this video, the slightly better compression rate does not compensate for the significantly longer encoding time for my purposes. However, the codec is much more complicated and even the hardware unit on the graphics card requires 8 minutes for the task. Re-encoding this particular video into H.265/HEVC results in a 330 MB file. And as a bonus, the workstation fans remain almost inaudible while the little fan in my notebook runs rampant for one and a half hours. Running the same task on my workstation and letting the graphics card do the H.265/HEVC decoding + re-encoding in H.264 format is done at 13 times the original video frame rate, i.e. In other words, transcoding the video takes around 1.5 hours. Compressing a 49 minute 2.9 GB video file encoded with HEVC (H.265) and made on a mobile phone to a low bit-rate H.264 encoded video with a size of 380 MB is done at around 0,6 of the original video frame rate on my notebook. The speed-up that can be reached mainly depends on the input data and the desired output codec and quality. Since then I have found further parameter improvements for ffmpeg and in some scenarios, my speed-up is now over 30x compared to running the same task on my notebook. As I wrote at the time, I could get a speed-up of up to 8x over my X250 notebook. One of the reasons I bought a used Z440 workstation with a 6 core Xeon CPU and an Nvidia graphics card back in December was to offload and speedup occasional video transcoding tasks.
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