用来存档一些课程老视频，搞不太明白怎么配合使用，尤其理论上-cq的值是不会超过-qmax的，但是实际设置上它可以超过qmax仍然正常工作并且会对视频质量产生影响。qmax理论上最大值51，但可以设更高，和51没有区别。cq 也是51最大，超了会报错
用一小段视频测了一下，命令行大概是
ffmpeg -hwaccel cuda -c:v hevc_nvenc -cq 41 -qmin 1 -qmax 33 -i in.mp4 out.mp4
以下是压缩参数，空白的就是没有设置参数：
| 压缩前3011KB | |||
|---|---|---|---|
| -cq | -qmin | -qmax | Output File (KB) |
| 21 | 1 | 36 | 10764 |
| 30 | 1 | 36 | 4441 |
| 38 | 1 | 36 | 1996 |
| 38 | 1993 | ||
| 49 | 1 | 51 | 522 |
| 48 | 1 | 51 | 597 |
| 47 | 1 | 51 | 677 |
| 46 | 1 | 51 | 762 |
| 45 | 1 | 51 | 855 |
| 44 | 1 | 51 | 978 |
| 43 | 1 | 51 | 1092 |
| 42 | 1 | 51 | 1255 |
| 41 | 1 | 51 | 1402 |
| 43 | 1092 | ||
| 1 | 41 | 5802 | |
| 41 | 1 | 51 | 1402 |
| 41 | 1 | 50 | 1402 |
| 41 | 1 | 49 | 1402 |
| 41 | 1 | 48 | 1402 |
| 41 | 1 | 47 | 1402 |
| 41 | 1 | 46 | 1402 |
| 41 | 1 | 45 | 1401 |
| 41 | 1 | 42 | 1404 |
| 41 | 1 | 41 | 1406 |
| 41 | 1 | 40 | 1405 |
| 41 | 1 | 39 | 1411 |
| 41 | 1 | 38 | 1412 |
| 41 | 1 | 37 | 1419 |
| 41 | 1 | 36 | 1463 |
| 41 | 1 | 35 | 1646 |
| 41 | 1 | 34 | 1821 |
| 41 | 1 | 33 | 2042 |
| 41 | 1 | 32 | 2273 |
| 41 | 1 | 31 | 2536 |
| 41 | 1 | 30 | 2821 |
| 41 | 1 | 29 | 3046 |
| 41 | 1 | 28 | 3379 |
| 51 | 1 | 36 | 1492 |
| 44 | 1 | 36 | 1492 |
| 43 | 1 | 36 | 1492 |
| 42 | 1 | 36 | 1492 |
| 41 | 1 | 36 | 1463 |
| 40 | 1 | 36 | 1492 |
| 39 | 1 | 36 | 1773 |
| 38 | 1 | 36 | 1996 |
| 37 | 1 | 36 | 2226 |
| 36 | 1 | 36 | 2484 |
| 35 | 1 | 36 | 2766 |
| 34 | 1 | 36 | 3009 |
| 33 | 1 | 36 | 3313 |
| 32 | 1 | 36 | 3656 |
| 31 | 1 | 36 | 4020 |
| 30 | 1 | 36 | 4441 |
| 29 | 1 | 36 | 4814 |
| 28 | 1 | 36 | 5300 |
| 27 | 1 | 36 | 5838 |
| 1 | 36 | 5709 | |
| 51 | 1 | 28 | 3379 |
| 41 | 1 | 28 | 3379 |
| 38 | 1 | 28 | 3379 |
| 35 | 1 | 28 | 3379 |
| 34 | 1 | 28 | 3379 |
| 33 | 1 | 28 | 3375 |
| 32 | 1 | 28 | 3675 |
| 31 | 1 | 28 | 4025 |
| 30 | 1 | 28 | 4444 |
| 29 | 1 | 28 | 4817 |
| 28 | 1 | 28 | 5300 |
| 27 | 1 | 28 | 5849 |
| 26 | 1 | 28 | 6394 |
| 25 | 1 | 28 | 6943 |
| 24 | 1 | 28 | 7882 |
| 23 | 1 | 28 | 8722 |
| 22 | 1 | 28 | 9458 |
| 21 | 1 | 28 | 10739 |
| 20 | 1 | 28 | 11796 |
| 1 | 28 | 5836 | |
| 25 | 10 | 28 | 6943 |
| 25 | 20 | 28 | 6912 |
| 25 | 21 | 28 | 6402 |
| 25 | 22 | 28 | 5907 |
| 25 | 23 | 28 | 5326 |
| 25 | 25 | 28 | 4456 |
| 25 | 26 | 28 | 4026 |
| 25 | 28 | 28 | 3379 |
| 28 | 5788 | ||
| 28 | 3369 | ||
| 41 | 1 | 18 | 8713 |
| 41 | 1402 | ||
| 51 | 1 | 36 | 1492 |