tails: A Place for Mastodon Posts

Unfortunately volume normalization only works on the overall volume. If spoken dialog happens during sound effects that are supposed to play on a separate speaker (but got mixed into the dialog due to downmixing to stereo), no amount of fiddling with EQ or volume normalization will boost just the dialog without also boosting the background noise (in the case of using even a 30 band EQ, it won’t work if there’s any background music, vocals, or sound effects in the same frequency range as speech).

If you want to boost dialog with only software, the best route to go is to get in before downmixing so you can boost the center channel before it gets irreversibly mixed with unwanted sound effects from other channels. Some players might have that option, but like I said if you’re playing from a set top box or streaming stick, you’re gonna need an additional piece of hardware in the chain to do this. If you have the video file itself, you can use ffmpeg’s audio filter to do a custom downmix using the -af flag. This way, you can use a downmixing algorithm like the Robert Collier night mode dialog downmix mapping which preserves original dialog volume (which actually is an improvement in some cases since some algorithms erroneously lower the dialog volume when downmixing to stereo) while slightly reducing music and other channel volume - you can adjust the weights used to boost center channel volume further as well.