xstack stretches inputs vertically in some situations

[hans.baldzuhn]

Summary of the bug:

I'm on windows, with the lastest build from ​https://github.com/BtbN/FFmpeg-Builds/releases

I want yo layout some images in a bigger image

If no image touches the bottom of the layout, the picture is stretched to touch it.

How to reproduce:

I'm assembling a simple checker in a 3x6 xtack layout

---

Command with 2 items on top line and 1 in midle line

ffmpeg -y -i C:\Users\hbaldzuhn\Pictures\checker.png -i "C:\Users\hbaldzuhn\Pictures\checker.png" -i "C:\Users\hbaldzuhn\Pictures\checker.png" -filter_complex "[0:v]scale=64:64[v0];[1:v]scale=64:64[v1];[2:v]scale=64:64[v2];[v0][v1][v2]xstack=inputs=3:fill=black:layout=64_64|64_0|320_0" -s 384x192 "C:\Users\hbaldzuhn\Pictures\checker.assembly1.png"

---

Command with all checker on top line

ffmpeg -y -i C:\Users\hbaldzuhn\Pictures\checker.png -i "C:\Users\hbaldzuhn\Pictures\checker.png" -filter_complex "[0:v]scale=64:64[v0];[1:v]scale=64:64[v1];[v0][v1]xstack=inputs=2:fill=black:layout=64_0|320_0" -s 384x192 "C:\Users\hbaldzuhn\Pictures\checker.assembly2.png"

---

Command with items on each lines

ffmpeg -y -i C:\Users\hbaldzuhn\Pictures\checker.png -i "C:\Users\hbaldzuhn\Pictures\checker.png" -i "C:\Users\hbaldzuhn\Pictures\checker.png" -i "C:\Users\hbaldzuhn\Pictures\checker.png" -filter_complex "[0:v]scale=64:64[v0];[1:v]scale=64:64[v1];[2:v]scale=64:64[v2];[3:v]scale=64:64[v3];[v0][v1][v2][v3]xstack=inputs=4:fill=black:layout=64_64|64_0|320_0|128_128" -s 384x192 "C:\Users\hbaldzuhn\Pictures\checker.assembly3.png"

Full command and log

ffmpeg.exe -y -i C:\Users\hbaldzuhn\Pictures\checker.png -i "C:\Users\hbaldzuhn\Pictures\checker.png" -i "C:\Users\hbaldzuhn\Pictures\checker.png" -filter_complex "[0:v]scale=64:64[v0];[1:v]scale=64:64[v1];[2:v]scale=64:64[v2];[v0][v1][v2]xstack=inputs=3:fill=black:layout=64_64|64_0|320_0" -s 384x192 "C:\Users\hbaldzuhn\Pictures\checker.assembly1.png"
ffmpeg version N-109226-g2ad199ae31-20221125 Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 12.2.0 (crosstool-NG 1.25.0.90_cf9beb1)
  configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug --disable-w32threads --enable-pthreads --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --disable-libpulse --enable-libvmaf --disable-libxcb --disable-xlib --enable-amf --enable-libaom --enable-libaribb24 --enable-avisynth --enable-chromaprint --enable-libdav1d --enable-libdavs2 --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --enable-frei0r --enable-libgme --enable-libkvazaar --enable-libass --enable-libbluray --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librist --enable-libssh --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --disable-libmfx --enable-libvpl --enable-openal --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopenmpt --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --disable-libdrm --disable-vaapi --enable-libvidstab --enable-vulkan --enable-libshaderc --enable-libplacebo --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --enable-libzvbi --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-ldexeflags= --extra-libs=-lgomp --extra-version=20221125
  libavutil      57. 43.100 / 57. 43.100
  libavcodec     59. 54.100 / 59. 54.100
  libavformat    59. 34.102 / 59. 34.102
  libavdevice    59.  8.101 / 59.  8.101
  libavfilter     8. 50.101 /  8. 50.101
  libswscale      6.  8.112 /  6.  8.112
  libswresample   4.  9.100 /  4.  9.100
  libpostproc    56.  7.100 / 56.  7.100
Input #0, png_pipe, from 'C:\Users\hbaldzuhn\Pictures\checker.png':
  Duration: N/A, bitrate: N/A
  Stream #0:0: Video: png, rgba(pc), 240x240 [SAR 3780:3780 DAR 1:1], 25 fps, 25 tbr, 25 tbn
Input #1, png_pipe, from 'C:\Users\hbaldzuhn\Pictures\checker.png':
  Duration: N/A, bitrate: N/A
  Stream #1:0: Video: png, rgba(pc), 240x240 [SAR 3780:3780 DAR 1:1], 25 fps, 25 tbr, 25 tbn
Input #2, png_pipe, from 'C:\Users\hbaldzuhn\Pictures\checker.png':
  Duration: N/A, bitrate: N/A
  Stream #2:0: Video: png, rgba(pc), 240x240 [SAR 3780:3780 DAR 1:1], 25 fps, 25 tbr, 25 tbn
Stream mapping:
  Stream #0:0 (png) -> scale:default
  Stream #1:0 (png) -> scale:default
  Stream #2:0 (png) -> scale:default
  xstack:default -> Stream #0:0 (png)
Press [q] to stop, [?] for help
Output #0, image2, to 'C:\Users\hbaldzuhn\Pictures\checker.assembly1.png':
  Metadata:
    encoder         : Lavf59.34.102
  Stream #0:0: Video: png, rgba(pc, gbr/unknown/unknown, progressive), 384x192 [SAR 3:2 DAR 3:1], q=2-31, 200 kb/s, 25 fps, 25 tbn
    Metadata:
      encoder         : Lavc59.54.100 png
[image2 @ 0000026068f376c0] The specified filename 'C:\Users\hbaldzuhn\Pictures\checker.assembly1.png' does not contain an image sequence pattern or a pattern is invalid.
[image2 @ 0000026068f376c0] Use a pattern such as %03d for an image sequence or use the -update option (with -frames:v 1 if needed) to write a single image.
frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.00 bitrate=N/A speed=   0x
video:3kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.

[hans.baldzuhn]

Source checker

[Elon Musk]

This bug report is invalid.

xstack never stretches anything, it just does copy.

Your command that produces stretcher output is caused by additional scale filter. The xstack filter never does padding to imaginary size, so use pad filter for that instead of -s WidthxHeight at end.