我正在使用 ffmpeg 從影片中提取幀，但過程非常緩慢。查看 CPU 使用情況，我發現 ffmpeg 僅使用了 50% 的 CPU。我也嘗試過添加-threads 4，但似乎沒有任何效果。我需要最大限度地提高這個過程的速度。我該怎麼做？
更新：所以我運行了一個測試，我首先嘗試單獨轉換一個視頻，得到以下結果：
ffmpeg version N-71959-g9253cc4 Copyright (c) 2000-2015 the FFmpeg developers
built with gcc 4.9.2 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enable-zlib
libavutil 54. 23.101 / 54. 23.101
libavcodec 56. 37.102 / 56. 37.102
libavformat 56. 32.100 / 56. 32.100
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 16.101 / 5. 16.101
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
libpostproc 53. 3.100 / 53. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'C:\1.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf55.33.100
Duration: 00:30:23.13, start: 0.000000, bitrate: 573 kb/s
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 640x360 [SAR 1:1 DAR 16:9], 501 kb/s, 29.97 fps, 29.97 tbr, 11988 tbn, 59.94 tbc (default)
Metadata:
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 32 kb/s (default)
Metadata:
handler_name : SoundHandler
Stream #0:2(und): Data: none (rtp / 0x20707472), 26 kb/s (default)
Metadata:
creation_time : 2014-08-27 16:05:35
handler_name : GPAC ISO Hint Handler
Stream #0:3(und): Data: none (rtp / 0x20707472), 7 kb/s (default)
Metadata:
creation_time : 2014-08-27 16:05:53
handler_name : GPAC ISO Hint Handler
[swscaler @ 0000000002e63360] deprecated pixel format used, make sure you did set range correctly
Output #0, image2, to 'C:\TEMP\1-%d.jpg':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf56.32.100
Stream #0:0(und): Video: mjpeg, yuvj420p(pc), 640x360 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 1 fps, 1 tbn, 1 tbc (default)
Metadata:
handler_name : VideoHandler
encoder : Lavc56.37.102 mjpeg
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> mjpeg (native))
Press [q] to stop, [?] for help
frame= 15 fps=0.0 q=1.6 size=N/A time=00:00:15.00 bitrate=N/A dup=0 drop=384
frame= 28 fps= 28 q=1.6 size=N/A time=00:00:28.00 bitrate=N/A dup=0 drop=763
frame= 42 fps= 28 q=1.6 size=N/A time=00:00:42.00 bitrate=N/A dup=0 drop=1172
frame= 55 fps= 27 q=1.6 size=N/A time=00:00:55.00 bitrate=N/A dup=0 drop=1529
frame= 67 fps= 27 q=1.6 size=N/A time=00:01:07.00 bitrate=N/A dup=0 drop=1896
frame= 80 fps= 27 q=1.6 size=N/A time=00:01:20.00 bitrate=N/A dup=0 drop=2267
frame= 93 fps= 27 q=1.6 size=N/A time=00:01:33.00 bitrate=N/A dup=0 drop=2651
frame= 106 fps= 26 q=1.6 size=N/A time=00:01:46.00 bitrate=N/A dup=0 drop=3025
frame= 119 fps= 26 q=1.6 size=N/A time=00:01:59.00 bitrate=N/A dup=0 drop=3386
frame= 131 fps= 26 q=1.6 size=N/A time=00:02:11.00 bitrate=N/A dup=0 drop=3757
frame= 144 fps= 26 q=1.6 size=N/A time=00:02:24.00 bitrate=N/A dup=0 drop=4124
frame= 157 fps= 26 q=1.6 size=N/A time=00:02:37.00 bitrate=N/A dup=0 drop=4487
frame= 169 fps= 26 q=1.6 size=N/A time=00:02:49.00 bitrate=N/A dup=0 drop=4852
frame= 182 fps= 26 q=1.6 size=N/A time=00:03:02.00 bitrate=N/A dup=0 drop=5226
frame= 195 fps= 26 q=1.6 size=N/A time=00:03:15.00 bitrate=N/A dup=0 drop=5593
frame= 209 fps= 26 q=1.6 size=N/A time=00:03:29.00 bitrate=N/A dup=0 drop=5990
frame= 222 fps= 26 q=1.6 size=N/A time=00:03:42.00 bitrate=N/A dup=0 drop=6367
frame= 235 fps= 26 q=1.6 size=N/A time=00:03:55.00 bitrate=N/A dup=0 drop=6753
frame= 248 fps= 26 q=1.6 size=N/A time=00:04:08.00 bitrate=N/A dup=0 drop=7131
frame= 261 fps= 26 q=1.6 size=N/A time=00:04:21.00 bitrate=N/A dup=0 drop=7497
frame= 274 fps= 26 q=1.6 size=N/A time=00:04:34.00 bitrate=N/A dup=0 drop=7873
frame= 287 fps= 26 q=1.6 size=N/A time=00:04:47.00 bitrate=N/A dup=0 drop=8255
frame= 300 fps= 26 q=1.6 size=N/A time=00:05:00.00 bitrate=N/A dup=0 drop=8644
frame= 314 fps= 26 q=1.6 size=N/A time=00:05:14.00 bitrate=N/A dup=0 drop=9036
frame= 328 fps= 26 q=1.6 size=N/A time=00:05:28.00 bitrate=N/A dup=0 drop=9438
frame= 340 fps= 26 q=1.6 size=N/A time=00:05:40.00 bitrate=N/A dup=0 drop=9813
frame= 354 fps= 26 q=1.6 size=N/A time=00:05:54.00 bitrate=N/A dup=0 drop=10205
frame= 367 fps= 26 q=1.6 size=N/A time=00:06:07.00 bitrate=N/A dup=0 drop=10585
frame= 380 fps= 26 q=1.6 size=N/A time=00:06:20.00 bitrate=N/A dup=0 drop=10961
frame= 394 fps= 26 q=1.6 size=N/A time=00:06:34.00 bitrate=N/A dup=0 drop=11360
frame= 406 fps= 26 q=1.6 size=N/A time=00:06:46.00 bitrate=N/A dup=0 drop=11712
frame= 420 fps= 26 q=1.6 size=N/A time=00:07:00.00 bitrate=N/A dup=0 drop=12103
frame= 434 fps= 26 q=1.6 size=N/A time=00:07:14.00 bitrate=N/A dup=0 drop=12509
frame= 447 fps= 26 q=1.6 size=N/A time=00:07:27.00 bitrate=N/A dup=0 drop=12888
frame= 460 fps= 26 q=1.6 size=N/A time=00:07:40.00 bitrate=N/A dup=0 drop=13267
frame= 473 fps= 26 q=1.6 size=N/A time=00:07:53.00 bitrate=N/A dup=0 drop=13640
frame= 486 fps= 26 q=1.6 size=N/A time=00:08:06.00 bitrate=N/A dup=0 drop=14036
frame= 500 fps= 26 q=1.6 size=N/A time=00:08:20.00 bitrate=N/A dup=0 drop=14421
frame= 513 fps= 26 q=1.6 size=N/A time=00:08:33.00 bitrate=N/A dup=0 drop=14808
frame= 526 fps= 26 q=1.6 size=N/A time=00:08:46.00 bitrate=N/A dup=0 drop=15197
frame= 540 fps= 26 q=1.6 size=N/A time=00:09:00.00 bitrate=N/A dup=0 drop=15579
frame= 552 fps= 26 q=1.6 size=N/A time=00:09:12.00 bitrate=N/A dup=0 drop=15948
frame= 565 fps= 26 q=1.6 size=N/A time=00:09:25.00 bitrate=N/A dup=0 drop=16321
frame= 579 fps= 26 q=1.6 size=N/A time=00:09:39.00 bitrate=N/A dup=0 drop=16725
frame= 592 fps= 26 q=1.6 size=N/A time=00:09:52.00 bitrate=N/A dup=0 drop=17097
frame= 605 fps= 26 q=1.6 size=N/A time=00:10:05.00 bitrate=N/A dup=0 drop=17462
frame= 618 fps= 26 q=1.6 size=N/A time=00:10:18.00 bitrate=N/A dup=0 drop=17851
frame= 631 fps= 26 q=1.6 size=N/A time=00:10:31.00 bitrate=N/A dup=0 drop=18225
frame= 644 fps= 26 q=1.6 size=N/A time=00:10:44.00 bitrate=N/A dup=0 drop=18607
frame= 657 fps= 26 q=1.6 size=N/A time=00:10:57.00 bitrate=N/A dup=0 drop=18969
frame= 669 fps= 26 q=1.6 size=N/A time=00:11:09.00 bitrate=N/A dup=0 drop=19333
frame= 681 fps= 26 q=1.6 size=N/A time=00:11:21.00 bitrate=N/A dup=0 drop=19681
frame= 693 fps= 26 q=1.6 size=N/A time=00:11:33.00 bitrate=N/A dup=0 drop=20026
frame= 706 fps= 26 q=1.6 size=N/A time=00:11:46.00 bitrate=N/A dup=0 drop=20402
frame= 716 fps= 26 q=1.6 size=N/A time=00:11:56.00 bitrate=N/A dup=0 drop=20691
frame= 726 fps= 26 q=1.6 size=N/A time=00:12:06.00 bitrate=N/A dup=0 drop=20985
frame= 738 fps= 26 q=1.6 size=N/A time=00:12:18.00 bitrate=N/A dup=0 drop=21317
frame= 751 fps= 26 q=1.6 size=N/A time=00:12:31.00 bitrate=N/A dup=0 drop=21692
frame= 763 fps= 26 q=1.6 size=N/A time=00:12:43.00 bitrate=N/A dup=0 drop=22049
frame= 775 fps= 26 q=1.6 size=N/A time=00:12:55.00 bitrate=N/A dup=0 drop=22403
frame= 788 fps= 26 q=1.6 size=N/A time=00:13:08.00 bitrate=N/A dup=0 drop=22764
frame= 801 fps= 26 q=1.6 size=N/A time=00:13:21.00 bitrate=N/A dup=0 drop=23149
frame= 814 fps= 26 q=1.6 size=N/A time=00:13:34.00 bitrate=N/A dup=0 drop=23540
frame= 828 fps= 26 q=1.6 size=N/A time=00:13:48.00 bitrate=N/A dup=0 drop=23937
frame= 841 fps= 26 q=1.6 size=N/A time=00:14:01.00 bitrate=N/A dup=0 drop=24315
frame= 854 fps= 26 q=1.6 size=N/A time=00:14:14.00 bitrate=N/A dup=0 drop=24694
frame= 867 fps= 26 q=1.6 size=N/A time=00:14:27.00 bitrate=N/A dup=0 drop=25071
frame= 881 fps= 26 q=1.6 size=N/A time=00:14:41.00 bitrate=N/A dup=0 drop=25458
frame= 894 fps= 26 q=1.6 size=N/A time=00:14:54.00 bitrate=N/A dup=0 drop=25844
frame= 908 fps= 26 q=1.6 size=N/A time=00:15:08.00 bitrate=N/A dup=0 drop=26240
frame= 923 fps= 26 q=1.6 size=N/A time=00:15:23.00 bitrate=N/A dup=0 drop=26675
frame= 935 fps= 26 q=1.6 size=N/A time=00:15:35.00 bitrate=N/A dup=0 drop=27038
frame= 949 fps= 26 q=1.6 size=N/A time=00:15:49.00 bitrate=N/A dup=0 drop=27431
frame= 961 fps= 26 q=1.6 size=N/A time=00:16:01.00 bitrate=N/A dup=0 drop=27776
frame= 973 fps= 26 q=1.6 size=N/A time=00:16:13.00 bitrate=N/A dup=0 drop=28125
frame= 985 fps= 26 q=1.6 size=N/A time=00:16:25.00 bitrate=N/A dup=0 drop=28477
frame= 998 fps= 26 q=1.6 size=N/A time=00:16:38.00 bitrate=N/A dup=0 drop=28848
frame= 1010 fps= 26 q=1.6 size=N/A time=00:16:50.00 bitrate=N/A dup=0 drop=29211
frame= 1023 fps= 26 q=1.6 size=N/A time=00:17:03.00 bitrate=N/A dup=0 drop=29572
frame= 1035 fps= 26 q=1.6 size=N/A time=00:17:15.00 bitrate=N/A dup=0 drop=29932
frame= 1047 fps= 26 q=1.6 size=N/A time=00:17:27.00 bitrate=N/A dup=0 drop=30294
frame= 1060 fps= 26 q=1.6 size=N/A time=00:17:40.00 bitrate=N/A dup=0 drop=30644
frame= 1072 fps= 26 q=1.6 size=N/A time=00:17:52.00 bitrate=N/A dup=0 drop=31004
frame= 1085 fps= 26 q=1.6 size=N/A time=00:18:05.00 bitrate=N/A dup=0 drop=31368
frame= 1097 fps= 26 q=1.6 size=N/A time=00:18:17.00 bitrate=N/A dup=0 drop=31742
frame= 1110 fps= 26 q=1.6 size=N/A time=00:18:30.00 bitrate=N/A dup=0 drop=32101
frame= 1123 fps= 26 q=1.6 size=N/A time=00:18:43.00 bitrate=N/A dup=0 drop=32493
frame= 1137 fps= 26 q=1.6 size=N/A time=00:18:57.00 bitrate=N/A dup=0 drop=32874
frame= 1150 fps= 26 q=1.6 size=N/A time=00:19:10.00 bitrate=N/A dup=0 drop=33251
frame= 1162 fps= 26 q=1.6 size=N/A time=00:19:22.00 bitrate=N/A dup=0 drop=33626
frame= 1175 fps= 26 q=1.6 size=N/A time=00:19:35.00 bitrate=N/A dup=0 drop=33990
frame= 1188 fps= 26 q=1.6 size=N/A time=00:19:48.00 bitrate=N/A dup=0 drop=34362
frame= 1201 fps= 26 q=1.6 size=N/A time=00:20:01.00 bitrate=N/A dup=0 drop=34739
frame= 1214 fps= 26 q=1.6 size=N/A time=00:20:14.00 bitrate=N/A dup=0 drop=35127
frame= 1228 fps= 26 q=1.6 size=N/A time=00:20:28.00 bitrate=N/A dup=0 drop=35521
frame= 1242 fps= 26 q=1.6 size=N/A time=00:20:42.00 bitrate=N/A dup=0 drop=35916
frame= 1254 fps= 26 q=1.6 size=N/A time=00:20:54.00 bitrate=N/A dup=0 drop=36281
frame= 1267 fps= 26 q=1.6 size=N/A time=00:21:07.00 bitrate=N/A dup=0 drop=36661
frame= 1280 fps= 26 q=1.6 size=N/A time=00:21:20.00 bitrate=N/A dup=0 drop=37017
frame= 1293 fps= 26 q=1.6 size=N/A time=00:21:33.00 bitrate=N/A dup=0 drop=37394
frame= 1306 fps= 26 q=1.6 size=N/A time=00:21:46.00 bitrate=N/A dup=0 drop=37786
frame= 1318 fps= 26 q=1.6 size=N/A time=00:21:58.00 bitrate=N/A dup=0 drop=38142
frame= 1332 fps= 26 q=1.6 size=N/A time=00:22:12.00 bitrate=N/A dup=0 drop=38526
frame= 1346 fps= 26 q=1.6 size=N/A time=00:22:26.00 bitrate=N/A dup=0 drop=38929
frame= 1358 fps= 26 q=1.6 size=N/A time=00:22:38.00 bitrate=N/A dup=0 drop=39303
frame= 1371 fps= 26 q=1.6 size=N/A time=00:22:51.00 bitrate=N/A dup=0 drop=39676
frame= 1384 fps= 26 q=1.6 size=N/A time=00:23:04.00 bitrate=N/A dup=0 drop=40046
frame= 1398 fps= 26 q=1.6 size=N/A time=00:23:18.00 bitrate=N/A dup=0 drop=40438
frame= 1411 fps= 26 q=1.6 size=N/A time=00:23:31.00 bitrate=N/A dup=0 drop=40818
frame= 1424 fps= 26 q=1.6 size=N/A time=00:23:44.00 bitrate=N/A dup=0 drop=41202
frame= 1437 fps= 26 q=1.6 size=N/A time=00:23:57.00 bitrate=N/A dup=0 drop=41589
frame= 1451 fps= 26 q=1.6 size=N/A time=00:24:11.00 bitrate=N/A dup=0 drop=41971
frame= 1463 fps= 26 q=1.6 size=N/A time=00:24:23.00 bitrate=N/A dup=0 drop=42340
frame= 1477 fps= 26 q=1.6 size=N/A time=00:24:37.00 bitrate=N/A dup=0 drop=42724
frame= 1490 fps= 26 q=1.6 size=N/A time=00:24:50.00 bitrate=N/A dup=0 drop=43129
frame= 1503 fps= 26 q=1.6 size=N/A time=00:25:03.00 bitrate=N/A dup=0 drop=43500
frame= 1516 fps= 26 q=1.6 size=N/A time=00:25:16.00 bitrate=N/A dup=0 drop=43869
frame= 1530 fps= 26 q=1.6 size=N/A time=00:25:30.00 bitrate=N/A dup=0 drop=44260
frame= 1543 fps= 26 q=1.6 size=N/A time=00:25:43.00 bitrate=N/A dup=0 drop=44646
frame= 1556 fps= 26 q=1.6 size=N/A time=00:25:56.00 bitrate=N/A dup=0 drop=45033
frame= 1569 fps= 26 q=1.6 size=N/A time=00:26:09.00 bitrate=N/A dup=0 drop=45393
frame= 1582 fps= 26 q=1.6 size=N/A time=00:26:22.00 bitrate=N/A dup=0 drop=45766
frame= 1594 fps= 26 q=1.6 size=N/A time=00:26:34.00 bitrate=N/A dup=0 drop=46139
frame= 1607 fps= 26 q=1.6 size=N/A time=00:26:47.00 bitrate=N/A dup=0 drop=46498
frame= 1620 fps= 26 q=1.6 size=N/A time=00:27:00.00 bitrate=N/A dup=0 drop=46874
frame= 1633 fps= 26 q=1.6 size=N/A time=00:27:13.00 bitrate=N/A dup=0 drop=47247
frame= 1645 fps= 26 q=1.6 size=N/A time=00:27:25.00 bitrate=N/A dup=0 drop=47609
frame= 1659 fps= 26 q=1.6 size=N/A time=00:27:39.00 bitrate=N/A dup=0 drop=48000
frame= 1671 fps= 26 q=1.6 size=N/A time=00:27:51.00 bitrate=N/A dup=0 drop=48362
frame= 1684 fps= 26 q=1.6 size=N/A time=00:28:04.00 bitrate=N/A dup=0 drop=48748
frame= 1697 fps= 26 q=1.6 size=N/A time=00:28:17.00 bitrate=N/A dup=0 drop=49103
frame= 1710 fps= 26 q=1.6 size=N/A time=00:28:30.00 bitrate=N/A dup=0 drop=49474
frame= 1723 fps= 26 q=1.6 size=N/A time=00:28:43.00 bitrate=N/A dup=0 drop=49858
frame= 1736 fps= 26 q=1.6 size=N/A time=00:28:56.00 bitrate=N/A dup=0 drop=50249
frame= 1749 fps= 26 q=1.6 size=N/A time=00:29:09.00 bitrate=N/A dup=0 drop=50612
frame= 1762 fps= 26 q=1.6 size=N/A time=00:29:22.00 bitrate=N/A dup=0 drop=50981
frame= 1774 fps= 26 q=1.6 size=N/A time=00:29:34.00 bitrate=N/A dup=0 drop=51349
frame= 1787 fps= 26 q=1.6 size=N/A time=00:29:47.00 bitrate=N/A dup=0 drop=51727
frame= 1800 fps= 26 q=1.6 size=N/A time=00:30:00.00 bitrate=N/A dup=0 drop=52098
frame= 1813 fps= 26 q=1.6 size=N/A time=00:30:13.00 bitrate=N/A dup=0 drop=52486
frame= 1824 fps= 26 q=1.6 Lsize=N/A time=00:30:24.00 bitrate=N/A dup=0 drop=52798
video:40987kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
整個過程耗時71秒，幀率為26，CPU使用率50%。
然後我嘗試使用相同的影片但具有 2 個並行任務來運行相同的轉換（基本上將其轉換 2 次並使用 2 個不同的名稱儲存圖像）。每個影片的幀率穩定在 17 左右，每個進度的 CPU 使用率 45，總時間第一個為 105 秒，第二個為 104 秒。所以依序運行它們需要 70+70=140 秒，而同時運行 2 個實例，迫使 CPU 100% 工作需要 105 秒才能完成兩個視訊的轉換，節省了 35 秒，這在很大程度上節省了時間很重要。
答案1
寫入許多小文件很慢。這就是為什麼 CPU 沒有達到 100% 負載，但硬碟可能達到 100% 負載的原因。
這當然不是指以 100% 可能的吞吐量寫入，而是指磁碟處理請求的速度。由於建立文件涉及對磁碟上許多可能相距很遠的區域的訪問，因此磁碟的訪問延遲是此處的瓶頸。
對此您無能為力，只能切換到 SSD 或更快的 SSD。 RAID0 不太可能幫助解決受延遲限制的負載。