video.mp4

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/storage/emulated/0/vid.mp4':
      Metadata:
        major_brand     : mp42
        minor_version   : 0
        compatible_brands: isommp42
        creation_time   : 2019-07-26T03:28:49.000000Z
        com.android.version: 8.0.0
      Duration: 00:00:07.64, start: 0.000000, bitrate: 20534 kb/s
        Stream #0:0(eng): Video: h264 (avc1 / 0x31637661), yuvj420p(pc, smpte170m), 1920x1080, 20966 kb/s, SAR 1:1 DAR 16:9, 29.70 fps, 29.75 tbr, 90k tbn, 180k tbc (default)
        Metadata:
          rotate          : 270
          creation_time   : 2019-07-26T03:28:49.000000Z
          handler_name    : VideoHandle
        Side data:
          displaymatrix: rotation of 90.00 degrees
        Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 96 kb/s (default)
        Metadata:
          creation_time   : 2019-07-26T03:28:49.000000Z
          handler_name    : SoundHandle


sunflower.mp3

Input #0, mp3, from '/storage/emulated/0/sunflower.mp3':
      Metadata:
        album           : Sunflower (Spider-Man: Into the Spider-Verse) - Single
        composer        : Louis Bell, Carter Lang, Austin Richard Post, Billy Walsh & Khalif Malik Ibin Shaman Brown
        genre           : Hip-Hop/Rap
        copyright       : This Compilation ℗ 2018 Republic Records, a division of UMG Recordings, Inc.
        title           : Sunflower (Spider-Man: Into the Spider-Verse)
        artist          : Post Malone & Swae Lee
        album_artist    : Post Malone & Swae Lee
        track           : 01/01
        TYER            : 2018-10-18T07:00:00Z
      Duration: 00:02:38.07, start: 0.000000, bitrate: 325 kb/s
        Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 320 kb/s
        Stream #0:1: Video: mjpeg, yuvj444p(pc, bt470bg/unknown/unknown), 1400x1400 [SAR 300:300 DAR 1:1], 90k tbr, 90k tbn, 90k tbc
        Metadata:
          comment         : Cover (front)




On ubuntu:
ffmpeg version 3.4.6-0ubuntu0.18.04.1

The following command works fine on ubuntu...

ffmpeg -i video.mp4 -i sunflower.mp3 -map 0:v -c:v copy -filter_complex '[0:a][1:a]amix[aout]' -map '[aout]' -shortest out.mp4




On Android:
ffmpeg version n4.0-39-gda39990

The following command doesn't work on android...

ffmpeg -i /storage/emulated/0/Camera/video.mp4 -i /storage/emulated/0/sunflower.mp3 -map 0:v -c:v copy -filter_complex '[0:a][1:a]amix[aout]' -map '[aout]' -shortest /storage/emulated/0/out.mp4

The error I get is...

[AVFilterGraph @ 0xf016f040] No such filter: '[0:a][1:a]amix[aout]'

All of the files are present and I can do 'ffmpeg -i <file>' on both the files and the output is expected, so the files are present and can be read by the ffmpeg binary