ffmpeg greenscreen transparent while using color palette

Question

I have a video that has a color I'd like to remove, and make into a transparent gif with ffmpeg. I first created a color palette using

ffmpeg -i video.mp4 -filter_complex "[0:v] palettegen" palette.png=

that went fine. Then when I go to try and make a gif I do this:

ffmpeg -i Untitled.mp4 -i palette.png -filter_complex "[0:v][1:v] paletteuse;[0:v]chromakey=0xE700F4" out.gif

This however gives an error and does not create anything. Am I doing something wrong here?

here's the log:

  built with gcc 9.1.1 (GCC) 20190621
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  libavutil      56. 30.100 / 56. 30.100
  libavcodec     58. 53.101 / 58. 53.101
  libavformat    58. 28.101 / 58. 28.101
  libavdevice    58.  7.100 / 58.  7.100
  libavfilter     7. 56.101 /  7. 56.101
  libswscale      5.  4.101 /  5.  4.101
  libswresample   3.  4.100 /  3.  4.100
  libpostproc    55.  4.100 / 55.  4.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Untitled.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 19529854
    compatible_brands: mp42isom
    creation_time   : 2019-07-10T05:06:10.000000Z
  Duration: 00:00:07.04, start: 0.000000, bitrate: 12629 kb/s
    Stream #0:0(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 190 kb/s (default)
    Metadata:
      creation_time   : 2019-07-10T05:06:10.000000Z
      handler_name    : Sound Media Handler
    Stream #0:1(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv), 1920x1080 [SAR 1:1 DAR 16:9], 12433 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
    Metadata:
      creation_time   : 2019-07-10T05:06:10.000000Z
      handler_name    : Video Media Handler
      encoder         : AVC Coding
Input #1, png_pipe, from 'palette.png':
  Duration: N/A, bitrate: N/A
    Stream #1:0: Video: png, rgba(pc), 16x16 [SAR 1:1 DAR 1:1], 25 tbr, 25 tbn, 25 tbc
Stream mapping:
  Stream #0:1 (h264) -> paletteuse:default
  Stream #0:1 (h264) -> chromakey
  Stream #1:0 (png) -> paletteuse:palette
  paletteuse -> Stream #0:0 (gif)
  chromakey -> Stream #0:1 (gif)
Press [q] to stop, [?] for help
[swscaler @ 0000008b903fedc0] No accelerated colorspace conversion found from yuva420p to bgr8.
[gif @ 0000008b8ca40540] GIF muxer supports only a single video GIF stream.
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument
Error initializing output stream 0:1 --
Conversion failed!

Answer 1

Your command is attempting to place two streams into the GIF output (the output from paletteuse and the output from chromakey), but the GIF muxer supports only a single stream. To fix this your outputs from each filter should not be orphaned. See the filtering introduction for more info.

ffmpeg -i input.mp4 -filter_complex "[0:v]chromakey=0xE700F4,split[v0][v1];[v0]palettegen[p];[v1][p]paletteuse" output.gif

• For better results use the chromakey filter before creating the palette.
• With the split filter you can avoid making a temporary palette file.