$ ls -1 *.jpg
1.jpg # could be any size, here is 210×315
2.jpg # could be any size, here is 480x480
3.jpg # could be any size, here is 480x480
$ ls -1 *.png
bg.png # 480x160
$ ffmpeg -y -r 0.5 -pattern_type glob -i '*.jpg' -i bg.png -filter_complex 'scale=iw*min(480/iw\,480/ih):ih*min(480/iw\,480/ih),pad=480:480:(480-iw*min(480/iw\,480/ih))/2:(480-ih*min(480/iw\,480/ih))/2,vstack' -vsync vfr -c:v libx264 -pix_fmt yuv420p out.mp4
...
$ ffprobe out.mp4
ffprobe version 3.3.2 Copyright (c) 2007-2017 the FFmpeg developers
built with Apple LLVM version 8.1.0 (clang-802.0.42)
configuration: --prefix=/usr/local/Cellar/ffmpeg/3.3.2 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libfreetype --enable-libmp3lame --enable-libx264 --enable-libxvid --enable-opencl --disable-lzma --enable-vda
libavutil 55. 58.100 / 55. 58.100
libavcodec 57. 89.100 / 57. 89.100
libavformat 57. 71.100 / 57. 71.100
libavdevice 57. 6.100 / 57. 6.100
libavfilter 6. 82.100 / 6. 82.100
libavresample 3. 5. 0 / 3. 5. 0
libswscale 4. 6.100 / 4. 6.100
libswresample 2. 7.100 / 2. 7.100
libpostproc 54. 5.100 / 54. 5.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'out.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf57.71.100
Duration: 00:00:02.00, start: 0.000000, bitrate: 152 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 480x640 [SAR 1:1 DAR 3:4], 149 kb/s, 0.50 fps, 0.50 tbr, 16384 tbn, 1 tbc (default)
Metadata:
handler_name : VideoHandler
视频大小480x640是正确的，但它只持续2秒，只包含第一张图片1.jpg，请告诉我如何解决这个问题？