How to improve video quality after using "filter_complex" ffmopeg command?

Question

I'm using the afir filter to add reverb effects in the video using the following command.

val reverbFFmpegCommand = arrayOf(
                        "-i",
                        originalVideoPath,
                        "-i",
                        reverbIRFileTypePath,
                        "-filter_complex",
                        "[0] [1] afir=dry=$dryValue:wet=$wetValue [reverb]; [0] [reverb] amix=inputs=2:weights=$originalWeightValue $reverbWeightValue",
                        reverbVideoPath
                    )

But the output video quality is very low than the original video quality. Seems like the video bitrate is very low in the output video.

Please help, how can the video quality be improved?