Access ReplayGain metadata through the Emby API for audio playback

[MarvinB 5]

I am the developer of Ear Wax, an Alexa music client that streams tracks from Emby Server 4.9.3.0.

Emby’s FFmpeg transcode log confirms that it detects embedded ReplayGain tags. For example:

REPLAYGAIN_TRACK_GAIN: -2.85 dB
REPLAYGAIN_TRACK_PEAK: 0.861816
REPLAYGAIN_ALBUM_GAIN: -2.16 dB
REPLAYGAIN_ALBUM_PEAK: 1.000000

The corresponding item is available through /emby/Audio/{Id}/stream.mp3, but requesting the complete item through /emby/Users/{UserId}/Items/{Id} does not return any gain, peak, ReplayGain, loudness, or normalization fields.

Is there a supported API endpoint or optional field that returns these embedded ReplayGain values before playback?

If not, is there a supported audio-streaming parameter that tells Emby’s transcoder to apply track ReplayGain during progressive MP3 transcoding?

The goal is track-to-track volume consistency. I would prefer to use Emby’s existing metadata and transcoder without requiring users to install a custom plugin or modify their media files.

I am specifically looking for:

• An API-accessible track gain and peak.
• A documented way to apply that gain during audio transcoding.
• Confirmation whether these capabilities are unavailable in Emby 4.9.3.0.

Thank you