Niestety nie mam Windy więc moje wyniki będą z Linuxa (ffmpeg). Bez akceleracji (h264):

Code (]
[libx264 @ 0x55ca987d89c0):

using SAR=1/1 [libx264 @ 0x55ca987d89c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 [libx264 @ 0x55ca987d89c0] profile High, level 4.2 [libx264 @ 0x55ca987d89c0] 264 - core 152 - H.264/MPEG-4 AVC codec - Copyleft 2003-2017 -   (You need to Login or Register - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00 Output #0, matroska, to 'Output.mkv':   Metadata:     encoder         : Lavf57.83.100     Stream #0:0: Video: h264 (libx264) (H264 / 0x34363248), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=-1--1, 50 fps, 1k tbn, 50 tbc     Metadata:       encoder         : Lavc57.107.100 libx264     Side data:       cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1     Stream #0:1: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, stereo, fltp, 256 kb/s frame= 1536 fps= 27 q=-1.0 Lsize=    7341kB time=00:00:30.68 bitrate=1959.6kbits/s speed=0.54x    video:6363kB audio:960kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.248693% [libx264 @ 0x55ca987d89c0] frame I:7     Avg QP:20.46  size: 39331 [libx264 @ 0x55ca987d89c0] frame P:384   Avg QP:23.55  size:  6176 [libx264 @ 0x55ca987d89c0] frame B:1145  Avg QP:24.73  size:  3378 [libx264 @ 0x55ca987d89c0] consecutive B-frames:  0.5%  0.0%  1.4% 98.2% [libx264 @ 0x55ca987d89c0] mb I  I16..4: 15.6% 76.8%  7.5% [libx264 @ 0x55ca987d89c0] mb P  I16..4:  0.3%  0.5%  0.0%  P16..4: 24.7%  1.7%  2.9%  0.0%  0.0%    skip:70.0% [libx264 @ 0x55ca987d89c0] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8: 41.3%  0.1%  0.0%  direct: 0.0%  skip:58.6%  L0:51.9% L1:48.0% BI: 0.0% [libx264 @ 0x55ca987d89c0] 8x8 transform intra:72.8% inter:97.7% [libx264 @ 0x55ca987d89c0] coded y,uvDC,uvAC intra: 42.9% 19.7% 1.4% inter: 3.2% 4.1% 0.0% [libx264 @ 0x55ca987d89c0] i16 v,h,dc,p: 30% 23% 25% 22% [libx264 @ 0x55ca987d89c0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 28% 17% 38%  3%  3%  3%  3%  2%  2% [libx264 @ 0x55ca987d89c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 35% 19% 18%  5%  5%  5%  4%  4%  4% [libx264 @ 0x55ca987d89c0] i8c dc,h,v,p: 75% 13% 11%  1% [libx264 @ 0x55ca987d89c0] Weighted P-Frames: Y:0.0% UV:0.0% [libx264 @ 0x55ca987d89c0] ref P L0: 56.6%  7.9% 24.6% 10.9% [libx264 @ 0x55ca987d89c0] ref B L0: 83.1% 13.6%  3.3% [libx264 @ 0x55ca987d89c0] ref B L1: 92.1%  7.9% [libx264 @ 0x55ca987d89c0] kb/s:1696.53 real    0m56.934s

Z akceleracją nvenc. Niestety mam za starą kartę (GTX750Ti) i nvenc_hevc nie jest obsługiwane:

Code (]
Output #0, matroska, to 'Output.mkv':
  Metadata:
    encoder         : Lavf57.83.100
    Stream #0:0: Video: h264 (h264_nvenc) (Main) (H264 / 0x34363248), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9):

, q=-1--1, 2000 kb/s, 50 fps, 1k tbn, 50 tbc     Metadata:       encoder         : Lavc57.107.100 h264_nvenc     Side data:       cpb: bitrate max/min/avg: 0/0/2000000 buffer size: 4000000 vbv_delay: -1     Stream #0:1: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, stereo, fltp, 256 kb/s frame= 1536 fps=240 q=26.0 Lsize=    4927kB time=00:00:30.70 bitrate=1314.8kbits/s speed=4.81x    video:3949kB audio:960kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.371204% real    0m6.533s

Podsumowując:
CPU (Xeon E5540): 57s
GPU (GTX750Ti): 6.5s