ffmpeg : audio + image to video : reduce time and space it takes

Question

我正在使用 FFMPEG 将图像和音频转换为视频。
我可以使用以下命令实现最终视频(也附加命令的输出):

time ffmpeg -loop 1 -i inputImage.jpg -i inputAudio.mp3 -c:v libx264 -
c:a copy -shortest output1.mp4
ffmpeg version 4.1.3-0york1~16.04 Copyright (c) 2000-2019 the FFmpeg 
developers
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.11) 20160609
  configuration: --prefix=/usr --extra-version='0york1~16.04' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-nonfree --enable-libfdk-aac --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
  libpostproc    55.  3.100 / 55.  3.100
Input #0, image2, from 'inputImage.jpg':
  Duration: 00:00:00.04, start: 0.000000, bitrate: 32003 kb/s
    Stream #0:0: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 4160x2340 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 25 tbn, 25 tbc
[mp3 @ 0x55cd4bed0f80] Estimating duration from bitrate, this may be inaccurate
Input #1, mp3, from 'inputAudio.mp3':
  Duration: 00:00:23.77, start: 0.000000, bitrate: 127 kb/s
    Stream #1:0: Audio: mp3, 44100 Hz, mono, fltp, 128 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> h264 (libx264))
  Stream #1:0 -> #0:1 (copy)
Press [q] to stop, [?] for help
[libx264 @ 0x55cd4bee9c80] using SAR=1/1
[libx264 @ 0x55cd4bee9c80] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x55cd4bee9c80] profile High, level 6.0
[libx264 @ 0x55cd4bee9c80] 264 - core 155 r2917 0a84d98 - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - http://www.videolan.org/x264.html - 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=6 lookahead_threads=1 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, mp4, to 'output1.mp4':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuvj420p(pc), 4160x2340 [SAR 1:1 DAR 16:9], q=-1--1, 25 fps, 12800 tbn, 25 tbc
    Metadata:
      encoder         : Lavc58.35.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
    Stream #0:1: Audio: mp3 (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 128 kb/s
frame=  647 fps= 21 q=28.0 Lsize=    1302kB time=00:00:23.76 bitrate= 449.0kbits/s speed=0.778x    
video:908kB audio:371kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.797463%
[libx264 @ 0x55cd4bee9c80] frame I:3     Avg QP:12.36  size:235361
[libx264 @ 0x55cd4bee9c80] frame P:163   Avg QP:17.66  size:   469
[libx264 @ 0x55cd4bee9c80] frame B:481   Avg QP:20.95  size:   336
[libx264 @ 0x55cd4bee9c80] consecutive B-frames:  0.8%  0.3%  0.0% 98.9%
[libx264 @ 0x55cd4bee9c80] mb I  I16..4: 60.6% 37.5%  1.9%
[libx264 @ 0x55cd4bee9c80] mb P  I16..4:  0.0%  0.0%  0.0%  P16..4:  0.3%  0.0%  0.0%  0.0%  0.0%    skip:99.7%
[libx264 @ 0x55cd4bee9c80] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  0.2%  0.0%  0.0%  direct: 0.0%  skip:99.8%  L0:46.7% L1:53.3% BI: 0.0%
[libx264 @ 0x55cd4bee9c80] 8x8 transform intra:36.9% inter:94.7%
[libx264 @ 0x55cd4bee9c80] coded y,uvDC,uvAC intra: 29.0% 60.8% 5.5% inter: 0.0% 0.1% 0.0%
[libx264 @ 0x55cd4bee9c80] i16 v,h,dc,p: 19% 67% 14%  0%
[libx264 @ 0x55cd4bee9c80] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu:  8% 42% 41%  1%  0%  0%  0%  0%  8%
[libx264 @ 0x55cd4bee9c80] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 35% 60%  5%  0%  0%  0%  0%  0%  0%
[libx264 @ 0x55cd4bee9c80] i8c dc,h,v,p: 24% 56% 16%  5%
[libx264 @ 0x55cd4bee9c80] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x55cd4bee9c80] ref P L0: 96.2%  0.0%  1.8%  2.0%
[libx264 @ 0x55cd4bee9c80] ref B L0: 87.7%  8.6%  3.7%
[libx264 @ 0x55cd4bee9c80] ref B L1: 98.5%  1.5%
[libx264 @ 0x55cd4bee9c80] kb/s:291.81

real    0m30.671s
user    1m50.724s
sys 0m0.348s

以下是受尊重的输入和输出大小:

inputImage.jpg : 160kb

inputAudio.mp3 : 380.3kb

output1.mp4 : 1.3MB

与输入音频相比，输出视频的大小相当大。这是我的第一个问题。
其次，正如你所看到的，这个过程大约需要 30 秒，我认为这太多了。
我该如何解决这两个问题？

减小输出视频文件大小

减少此过程所需的时间。

我已经浏览了许多在线链接，包括过去几个小时在这个论坛上提出的很多问题，但仍然无法解决这个问题。
尝试以帧速率播放，但会干扰输出视频的持续时间。
有人可以在这里帮忙吗。让我知道是否需要任何其他信息。
帮助我将最终视频的大小从 3MB 减少到 1.2MB 的一件事是压缩我正在使用的图像。

Answer 1

您的两个问题都是由于相同的原因造成的。 FFmpeg 通过重复图像 647 次来生成视频。您的输出文件有 647 个 21 FPS 的视频帧。此信息显示在您的控制台输出中。
frame= 647 fps= 21 q=28.0 Lsize= 1302kB time=00:00:23.76 bitrate= 449.0kbits/s speed=0.778x
您可以通过以下一种或多种方式进行优化

降低输出视频分辨率(-s 降低分辨率)

降低输出视频比特率(-vb lower-video-bitrate)

降低输出 FPS (-r lower-frame-rate)