ffmpeg pipe Invalid data found when processing input

Question

Here is my configuration.

const ffmpegPath = require('@ffmpeg-installer/ffmpeg').path;
const spawn = require('child_process').spawn;

ffmpeg = spawn(ffmpegPath, [
      
// Remove this line, as well as `-shortest`, if you send audio from the browser.
      // '-f', 'lavfi', '-i', 'anullsrc',

      // FFmpeg will read input video from STDIN
      '-i', '-',

      // -re flag means to Read input at native frame rate.
      '-re', '-y',

      // thread_queue_size added to avoid err: Thread message queue blocking; consider raising the thread_queue_size option, required before each input - this is for image2
      // '-thread_queue_size', '2048',

      // REF TO OVERLAY 
      // https://stackoverflow.com/questions/10438713/overlay-animated-images-with-transparency-over-a-static-background-image-using-f?rq=1
      // -loop loops the background image input so that we don't just have one frame, crucial!

      // The image file muxer writes video frames to image files, http://underpop.online.fr/f/ffmpeg/help/image2-1.htm.gz
      '-f', 'image2',

      // The -loop option is specific to the image file demuxer and gif muxer, so it can't be used for typical video files, but it can be used to infinitely loop a series of input images.
      '-loop', '1',

      // pattern_type is used to determine the format of the images contained in the files.
      // Read images matching the "*.png" glob pattern, that is files terminating with the ".png" suffix
      '-pattern_type', 'glob',

      // '-i', `images/${streamConfigData.youtube_key}/destination/image-*.png`,

      '-i', `images/${streamConfigData.youtube_key}/overlay/abc.png`,

      // '-vf', 'scale=1920x1080:flags=lanczos',
      
      // -shortest ends encoding when the shortest input ends, which is necessary as looping the background means that that input will never end.
      // 'overlay=shortest=1',

      "-filter_complex", "[1:v]format=rgba,colorchannelmixer=aa=1[fg];[0][fg]overlay",
      
      // Because we're using a generated audio source which never ends,
      // specify that we'll stop at end of other input.  Remove this line if you
      // send audio from the browser.
      // '-shortest',
      
      // If we're encoding H.264 in-browser, we can set the video codec to 'copy'
      // so that we don't waste any CPU and quality with unnecessary transcoding.
      // If the browser doesn't support H.264, set the video codec to 'libx264'
      // or similar to transcode it to H.264 here on the server.
      // '-vcodec', 'libx264',
      // it is not possible to filter and stream copy the same stream at the same time. https://stackoverflow.com/a/53526514/4057143
      '-vcodec', 'copy',
      
      // if browser not supports encoding AAC, we must transcode the audio to AAC here on the server.
      // '-acodec', 'aac',

      // Use this rate control mode if you want to keep the best quality and care less about the file size. CRF scale is 0–51, where 0 is lossless, 23 is the default, and 51 is worst quality possible. A lower value generally leads to higher quality, https://trac.ffmpeg.org/wiki/Encode/H.264
      '-crf', '23',

      // preset provide a certain encoding speed to compression ratio. A slower preset will provide better compression. medium – default preset, https://trac.ffmpeg.org/wiki/Encode/H.264
      '-preset', 'ultrafast',

      // -r set the frame rate. Generally, -r. Use the filter when you need to change framerate before applying further filters.
      // '-r', '30',
      // '-framerate', '30',

      //debug level logs
      '-loglevel', 'debug',
      '-v', 'verbose',

      // -g GOP_LEN_IN_FRAMES, -g sets the keyframe interval. https://superuser.com/a/908325
      '-g', '60',

      // video timescale, not sure what it is!
      '-video_track_timescale', '1000',

      // a live stream with more/less constant bit rate, to be able to control the bandwidth used.
      // a live stream with limited bit rate
      '-b:v', '15000k',
      // '-maxrate', '4000k',
      // '-bufsize', '8000k',

      // FLV is the container format used in conjunction with RTMP
      '-f', 'flv',
      
      // The output RTMP URL.
      // For debugging, you could set this to a filename like 'test.flv', and play
      // the resulting file with VLC.
      rtmpUrl 
    ], {
      env: {
          NODE_ENV: 'production',
          PATH: process.env.PATH
      }
    });