tvOS 11 audio/surround output options?

[Brenster]

Can anyone who has tried the betas of tvOS 11 on ATV 4 say if the audio/surround outputs have changed relative to tvOS 10?

Currently the options on 10 are:

1. Best Quality Available: Stereo is passed out as PCM stereo, Dolby Digital 5.1 is passed out as a Dolby Digital 5.1 bitstream for external decoding, Dolby Digital Plus 7.1 from iTunes movies is decoded on the ATV itself and passed out as 7.1 PCM.
2. Dolby Digital 5.1: DD 5.1 is Dolby Digital 5.1 is passed out as a Dolby Digital 5.1 bitstream for external decoding, Dolby Digital Plus 7.1 is downcoverted to DD 5.1 and passed out for external decoding.
3. Stereo: Everything is downconverter to PCM stereo and passed out

Trying to get an idea if tvOS 11 supports DD+ 7.1 being passed out as a bitstream for external decoding as per Amazon's Fire TV and Fire Stick.

If not, I'm hoping the forthcoming 4K Apple TV might support DD+ 7.1 bitstream output, or possibly even supporting Atmos bitstream.

 

[cardsdoc]

Also anxiously awaiting news of audio codec support in tvos11 and atv4/5. Would really like to have hd audio passthrough (Dolby and dts) plus Atmos so I can ditch using a media pc with Plex media player and just use one box.

Just to clarify above when best quality is selected there is no passthrough of DD bitstream. It's decoded, mixed with system sounds and passed on as pcm just as DD+ is. With Dolby digital selected it isn't actually a straight passthrough either. Atv decodes bitstream, mixes with system sounds and then re-encodes to DD bitstream. There has been much written about this but many feel this is why ATV looses dynamics relative to original bitstream. Something off with sound handling. Would much rather have my high end AVR handle all the decoding and know exactly what signal I am getting.

 

[Rigby]

Currently the options on 10 are:

1. Best Quality Available: Stereo is passed out as PCM stereo, Dolby Digital 5.1 is passed out as a Dolby Digital 5.1 bitstream for external decoding, Dolby Digital Plus 7.1 from iTunes movies is decoded on the ATV itself and passed out as 7.1 PCM.

I believe that's not accurate. This option outputs everything as uncompressed multi-channel PCM. I think that is currently the best option, since it is lossless at least for 48KHz/16 Bit content (assuming Apple implemented it right and doesn't mess around with the audio stream).

Dolby Digital 5.1: DD 5.1 is Dolby Digital 5.1 is passed out as a Dolby Digital 5.1 bitstream for external decoding, Dolby Digital Plus 7.1 is downcoverted to DD 5.1 and passed out for external decoding.

I suspect that the ATV may internally decode and then re-encode everything to DD if you choose that option (this would be necessary to to mix in sounds that the ATV itself generates, such as the "swish" sounds in the menu). If true, this could theoretically degrade sound quality, since the DD transcoding is a lossy process.

If not, I'm hoping the forthcoming 4K Apple TV might support DD+ 7.1 bitstream output, or possibly even supporting Atmos bitstream.

Atmos is the big one that would really require bitstreaming, since it cannot be losslessly transmitted via PCM. Generally, it would be great if they could implement real bitstreaming for all common formats (DD and TrueHD, DTS and DTS-HD MA, Atmos). I can really do without those "swish" sounds ...

 

[Brenster]

Also anxiously awaiting news of audio codec support in tvos11 and atv4/5. Would really like to have hd audio passthrough (Dolby and dts) plus Atmos so I can ditch using a media pc with Plex media player and just use one box.

Just to clarify above when best quality is selected there is no passthrough of DD bitstream. It's decoded, mixed with system sounds and passed on as pcm just as DD+ is. With Dolby digital selected it isn't actually a straight passthrough either. Atv decodes bitstream, mixes with system sounds and then re-encodes to DD bitstream. There has been much written about this but many feel this is why ATV looses dynamics relative to original bitstream. Something off with sound handling. Would much rather have my high end AVR handle all the decoding and know exactly what signal I am getting.

Happy to be corrected Hadn't thought about the injection of system sounds when DD 5.1 was selected on ATV and my receiver displaying 'Dolby Digital'.

Right there with you with wanting my receiver to handle the unmolested DD+ bitstream. Rented the live action beauty and the Beast via Fire TV last week; for all the films faults, the soundtrack is a thing of, well, beauty. Noticed that my receiver was handling the DD+ bitstream whereas ATV supplies pre-decoded PCM and the receiver displays Multi Ch In (Denon 3312).

That the Fire TV is happy passing over DD+ is the one thing I wish ATV has. If not in tvOS 11 then in ATV Next.

If you happen to know of any sites/forums discussing ATV and it's surround options as they relate to movies, I'd be most appreciative.

 

[bluespark]

Also anxiously awaiting news of audio codec support in tvos11 and atv4/5. Would really like to have hd audio passthrough (Dolby and dts) plus Atmos so I can ditch using a media pc with Plex media player and just use one box.

Just to clarify above when best quality is selected there is no passthrough of DD bitstream. It's decoded, mixed with system sounds and passed on as pcm just as DD+ is. With Dolby digital selected it isn't actually a straight passthrough either. Atv decodes bitstream, mixes with system sounds and then re-encodes to DD bitstream. There has been much written about this but many feel this is why ATV looses dynamics relative to original bitstream. Something off with sound handling. Would much rather have my high end AVR handle all the decoding and know exactly what signal I am getting.

Completely agree about audio passthrough. Those with good receivers are going to want the receiver to do all the work, even if that means giving up system sounds. To clarify, though, doesn't ATV4 subject stereo sound to the same audio processing to which it subjects multichannel audio? My ATV4 makes for a noticably poor stereo audio source, which I attribute to some sort of processing that must be occurring. The very same audio files played through most other devices sound better.