Unnecessary transcoding?

[Brian Murrell (Brian J. Murrell)]

BubbleUPnP thinks it needs to transcode a file with this metadata to a Chromecast 4K (sabrina):

Video: H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
Audio: ATSC A/52B (AC-3, E-AC-3)

Research seems to indicate that a sabrina can play this file directly.

Thoughts?

[Michael Pujos]

Chromecast does not natively support AC-3 and E-AC-3 (Dolby Digital and Dolby Digital+), thus the app transcodes the audio track 

to either mp3 (stereo) which is the default, or if 'Settings > Chromecast > Preserve multichannel audio' is enabled, to multichannel Opus.

Just the audio track of the video is transcoded, the video itself is unmodified, so it is a rather lightweight transcode that does not alter video quality.

If you have a Dolby Digital decoder hooked to your setup, you can try enabling 'AC-3 Passthrough' and 'E-AC-3 Passthrough' in Settings > Chromecast.