AppleTV 4 surround sound issue

DSP suggests, I suspect, that your ATV4->TV->Sherwood route is enforcing PCM 2.0 only audio, so the DSP processing is there to create a surround sound signal from a stereo source.

Jon Walker - yes - I agree. With Dolby Surround (sic) set as the output format I get 5.1 Dolby Digital output whenever playing back content - whether it is 2.0 or 5.1 content, and irrespective of the source codec.

When watching content in the Swedish SVT Play app (which is I think H264 720/25p video + stereo AAC audio) I get a 5.1 Dolby Digital stream sent to my amp wth silence in the surround channels

Jon Walker - I see slightly different functionality when replaying my own content. I've just created a 1080/24p H264 video file with AAC 2.0 and AC3 5.1 audio tracks.

With HDMI Audio output set to Auto (i.e. PCM with no limitation to stereo) :

The AAC 2.0 track is output to my receiver as PCM 2.0

The AC3 5.1 track is output my receiver as PCM 7.1

(In other words the PCM format output by the Apple TV is changing dynamically based on content - and isn't fixed at a 7.1 output all the time. This means that receiver decoding of older Dolby Stereo surround content which is recorded 2.0 but decoded using ProLogic or similar can be used, which is not always the case if you are outputting 7.1 or 5.1 with silence in the non-stereo channels)

There is an audible click in (not on the audio from) my Onkyo AVR as it switches from running in 2.0 to 7.1 - I'm guessing there are relays involved in 2.0 to 7.1 switching (as I had my amp configured for 2.0 content to be output to just the front left and right speakers, rather than being upmixed to 5.1 or 7.1)

There is an audible click in (not on the audio from) my Onkyo AVR as it switches from running in 2.0 to 7.1 - I'm guessing there are relays involved in 2.0 to 7.1 switching (as I had my amp configured for 2.0 content to be output to just the front left and right speakers, rather than being upmixed to 5.1 or 7.1)

Suspect it is a difference in our receivers. Your Onkyo is probably newer and/or "smarter" than my older Pioneer AVR. If I first reset my receiver to "Auto Surround," then it does switch over to "Pure Direct PCM 7.1" or "Stereo PCM" depending on the audio track selected for the particular file on the TV4. However, once it switches to 7.1 PCM, my receiver stays in this mode even if I change my audio track selection or switch to a different video file (which then defaults back to my stereo track). Basically, I suspect your AVR either rechecks channelization each time it detects "new" activity while mine may not auto-detect channelization changes when checking for a mode change. Same thing happens when set to "Dolby Surround" on the TV4 even though the same receiver connected to the older TV3 via the same HDMI connector used to correctly switch between stereo and surround Dolby content automatically. Not sure what's causing the "sticking" in conjunction with the new device. Have a feeling that system differences are going to make full analysis somewhat difficult here. Could get very confusing.

You can only mark one post as the solution, and you marked your own post.

Hopefully someone with an HDMI analyzer can check this. My AVR *always* reports PCM from my 4gen. In AUTO it's 7.1 (3/4/.1) or 2.0 (2/0/.0) depending on source type. In DOLBY SURROUND it's always 7.1 and in STEREO it's always 2.0. I think the 4g box always sends PCM with varying channel counts. Now if you were to take a naive look at my AVR status when the box is set to Dolby you might think it was Dolby Digital but that's simply the default "surround mode" label and Denon calls it Dolby Digital/DTS rather than "literal" or "untouched" as opposed to other mangling surround modes like "stadium", "club" or "multi-channel stereo".

My AVR can decode DD, DD+, DTS, TrueHD, MA etc. so if the TV (4g) can produce a bitstream then the HDMI handshake is broken.

I had a very similar problem with Netflix and movies - with Surround Sound set to Auto, I only got background sound effects and music coming through: no dialogue. As soon as I switched Surround Sound from "Auto" to the "Dolby Surround" setting, the problem disappeared.

I don't have any TV specific audio trouble with Netflix.

This issue is not solved for me, I have content that I encoded with both an AAC stereo audio stream and an AC3 audio stream, the new apple tv in auto mode outputs the aac stereo stream as prologix on my onkyo receiver into 7 channels. But when I put my apple tv into dolby digital mode it outputs the same aac stream into dolby digital on my onkyo but uses the stereo stream and then only outputs into the front 3 channels. this is maddening.

I can hook up my old apple tv gen 3 and the dolby digital is working properly with 5.1 output. Also on both new apple tvs I am have the audio play quiet for some reason, you can stop the movie and then start again and the audio plays at normal levels. this is definitely a bug that needs to be fixed, both of my gen 3 apple tvs do not have this behavior.

I have content that I encoded with both an AAC stereo audio stream and an AC3 audio stream, the new apple tv in auto mode outputs the aac stereo stream as prologix on my onkyo receiver into 7 channels. But when I put my apple tv into dolby digital mode it outputs the same aac stream into dolby digital on my onkyo but uses the stereo stream and then only outputs into the front 3 channels.

If you want to play the AAC stereo content in stereo, then try using the "Surround Sound > Stereo" setting with the AAC track selected to force output as stereo PCM. If you wish to "pass through" AC3 audio, try using the "Surround Sound > Dolby Surround" setting and manually selecting the AC3 track.

this is messed up. I really hope you guys understand when you change the setting from auto surround to Dolby on the Apple TV settings THAT YOU ARE NOT getting done Dolby digital sound. You may hear faint noise in background and you reciever will say Dolby digital but if you are NOT getting Dolby digital surround.

WHen hen you manually select Dolby on Apple TV the reciever says Dolby digital even when playing stereo context. Go check and the. You will realize I an right.

IF you manually select Dolby surround on Apple TV stereo context shouldn't play. But it does. And the reciever still says Dolby digital and the if you check you will notice only your front left and right speakers are outputting sound.

Same kind of problems here. 7.1 Decoded movies (Terminator Genesis and Netflix movies) show up at the receiver as 3/4/.1. So far so good. Front LR, Center, Surround LR do work. However, surround back speakers do not produce sound 😟.

When putting ATV to 'surround' instead of 'auto', receiver shows 3/2/.1 only, so 5.1 surround and NO 7.1.

7.1 For me is the main reason to buy ATV 😟 😟 😟