Error using ffmpeg and libvpx to encode webm from many images

Question

The command I use is:

C:\cmd\ffmpeg\bin\ffmpeg.exe -i "C:\Users\user\Dropbox\Workspace - C#\SnowflakeGenerator\out\out%d.png" -c:v libvpx -b:v 1M "C:\Users\user\Dropbox\Workspace - C#\SnowflakeGenerator\video.webm" -y 

The output was:

 ffmpeg version N-82889-g54931fd Copyright (c) 2000-2016 the FFmpeg developers built with gcc 5.4.0 (GCC) configuration: --enable-gpl --enable-version3 --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib libavutil 55. 43.100 / 55. 43.100 libavcodec 57. 68.100 / 57. 68.100 libavformat 57. 61.100 / 57. 61.100 libavdevice 57. 2.100 / 57. 2.100 libavfilter 6. 68.100 / 6. 68.100 libswscale 4. 3.101 / 4. 3.101 libswresample 2. 4.100 / 2. 4.100 libpostproc 54. 2.100 / 54. 2.100 Input #0, image2, from 'C:\Users\yb5243yv\Dropbox\Workspace - C#\SnowflakeGenerator\out\out%d.png': Duration: 00:00:21.04, start: 0.000000, bitrate: N/A Stream #0:0: Video: png, rgba(pc), 1000x1000 [SAR 3779:3779 DAR 1:1], 25 fps, 25 tbr, 25 tbn, 25 tbc [libvpx @ 0000000000be89c0] v1.6.0 [libvpx @ 0000000000be89c0] Transparency encoding with auto_alt_ref does not work Stream mapping: Stream #0:0 -> #0:0 (png (native) -> vp8 (libvpx)) Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height 

Error:

  [libvpx @ 0000000000be89c0] Transparency encoding with auto_alt_ref does not work 

and

 Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height 

I am not sure what exactly causes this problem, I followed this tutorial , however they did not mention the error. I should mention that I do not use audio, so I left the audio encoder (I tried it with an audio encoder to make sure, and this is not a problem)

Answer 1

Like the msg error, Transparency encoding with auto_alt_ref does not work , therefore

 ffmpeg.exe -i "out%d.png" -c:v libvpx -b:v 1M -auto-alt-ref 0 "video.webm" -y