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.

[Brian Murrell (Brian J. Murrell)]

Is this Preserve multichannel setting something that is remembered per Chromecast, so like if I have a CC that is connected through a receiver that will decode AC-3 and yet others that won't, I don't have to keep switching this back and forth depending on which CC I am currently casting to?

Additionally, it might be useful to inform the user that the transcoding that is necessary is audio-only, or even if it's simply remixing if that is all that is being done so that the user can understand the impact of the particular transcoding on their device.

[Michael Pujos]

Yes, the settings in Settings > Chromecast are global and apply to all Chromecast. 

And you are right, ideally some of these should be configurable per device. The reason it is not is historical

and date from a time where people would probably have just 1 Chromecast.

I will evaluate making this change but it is adding more complexity and settings.

Also displaying what exactly is transcoded is a good idea (remux only, video only, audio only, audio+video). I'm noting it but no promise it will make it.

Though be assured that only the minimum is transcoded.