Apple Event: May 7th at 7 am PT
So far:
Trailers app when decoding by default Dolby Digital is missing center channel output.
Tried a number of trailers, all missing center channel.
Model A1625
tvOS 9.0
Settings > Audio and Video > Surround Sound
The problem with Dolby Surround is discrete streams L and R are the only outputs with some apps.
Input displays as PCM. Therefore receiver decodes 5.1 or whatever. This is an improvement and preferable to the TVOS 9.0 behavior.
The ATV "TV" button makes the change pretty fast to go back and forth.
My ATV4 is connected by HDMI to a Pioneer Elite receiver and I also use the Pioneer app on ipad.
The problem is with Dolby Digital, some apps are only outputting 2 discrete streams L & R.
Receiver is displaying the following as inputs from ATV4 on a companion iPad app:
I leave the ATV4 in "Dolby Surround." Use the "TV" icon button to quickly switch back to settings>audio and change to "Auto" for the exceptions.
- Tried a number of trailers, all missing center channel.
- YouTube app when decoding by default Dolby Digital is missing center channel output.
- Tried a few other apps (HBO Go, Netflix, itunes movies previews, all produced a center channel output.
Trailers only play center channel content if originally encoded to do so. Most Apple trailers are encoded using an AAC stereo audio channel. For instance, I went to the TV4 and and selected a trailer at random. In this case, it was Gods of Egypt. It played just as you described. So, I then went to Apple's trailer web site and opened the trailer in the QT 7 Player and saved a copy of the file to my hard drive. Here are the specs for this trailer:
As I can't claim that all Apple trailers are encoded using stereo AAC audio tracks, it would be helpful if you would name a few of the trailers that interest you the most for similar examination of the source content.
As to your playback descriptions under different conditions, they appear to be accurate for an AAC stereo audio source as rendered by the TV4 in the "Auto" and "Dolby Surround" modes.
I Went back to atv3, and it seems atv3 handled Dolby Digital differently. If there was DD 5.1, atv3 output DD 5.1, if there wasn't, atv3 output pcm.
ATV4 however, if set to Dolby Surround, always outputs discrete Dolby Digital, even if there are only 2 channels of audio. ATV3 would drop the same down to PCM.
apple tv 3
settings > audio & video > dolby digital
itunes movies trailers, netflix, hbo go
itunes trailers, showtime anytime, youtube (dolby trailers)
itunes movies trailers, netflix, hbo go
itunes trailers, showtime anytime, youtube (dolby trailers)
everything: itunes movies trailers, netflix, hbo go, itunes trailers, showtime anytime, youtube (dolby trailers)
Here's what I've been using every time for each source:
Quick and dirty back to back test
Quick and dirty back to back test
Set sound to Dolby Digital
Go to iTunes Movies, and watch "Preview" for Mission Impossible rogue nation. Audio will be Dolby Digital 5.1
Go to Trailers, and watch Mission Impossible rogue nation "trailer 2" (same trailer as above). Audio is output PCM.
What makes you assume the iTunes Store sever's 2:25 AC3 5.1 encoded trailer is the same file as the Apple Trailer's server 2:29 AAC 2.0 DD ProLogic II encoded trailer?
You appear to be operating under the misconception that any DD5.1 bitstream connection between the TV4 and your AVR in the "Dolby Surround" output mode must a) be sourced from a Dolby encoded audio track and must b) contain 6 channels of audio. This is not true. If the source track is AAC mono, then the TV4 will, in the "Dolby Surround" mode, open a DD5.1 connection with your receiver but, under tvOS v9.0.1, will only "impress" the source center channel mono audio on the center channel of the DD5.1 bitstream. Since all other channels are "empty," the AVR then plays only the center "active" channel through your speaker system and thus plays the audio as it was originally encoded on the source AAC audio track.
In a similar manner, an AAC 2.0, stereo, or DD PL II audio track content will be "impressed" on the same DD5.1 connection as L and R audio along with four "empty" audio channels and only play back through your receiver's left and right front speakers. Further, since the DD5.1 connection tells your AVR the bitstream actually contains six discrete audio channels (four of which are "empty"), most receivers disable DD Digital PL II post processing capabilities and you are stuck with 2, and only 2, active channels playing back.
On the other hand, if the source track was originally encoded as AC3 (1.0, 2.0, stereo, DD PL II, or DD5.1) then the source encoded AC3 bitstream is sent to your AVR for proper DD Digital decoding and playback. Such AC3 encoded bitstreams are the only ones that play back with AVR channel activity indicators properly lit. I.e., a mono AC3 audio track will display as a center channel DD Digital encode, and L/R AC3 audio track as an L/R DD Digital encode, and an AC3 5.1 audio track as a 5.1 DD Digital encode. Further, if your AVR has a combined "Auto Surround + DD PL II" playback mode, and DD PL II encoded content will automatically be sent through the DD PL II decoder for DD PL II post processing. Unfortunately, my AVR employs two separate controls for this and I have to manually activate any DD PL II post processing if desired.
Since most TV4 apps employ the built-in TV4 "Surround Sound" for output, most apps will demonstrate the same manner of playback dependent only on the actual "Surround Sound" mode selected by the user and the actual track encode used as the audio source for output. In addition, many (if not most) Apple and third-party TV4 apps are programmed to "hide" the true nature of the sourced audio track encode and/or not offer the user an opportunity to select between AAC and AC3 source audio tracks. That is why I recommend you use an TV4 app like "Computers" along with test videos containing both AAC and AC3 audio tracks to tabulate how the TV4 "Dolby Surround" setting outputs differently encoded audio tracks employing different forms of channelization. I can post some test clips containing various combinations of AAC and AC3 encoded tracks if needed for testing on your system.
Jon Walker wrote:
Quick and dirty back to back test
Set sound to Dolby Digital
Go to iTunes Movies, and watch "Preview" for Mission Impossible rogue nation. Audio will be Dolby Digital 5.1
Go to Trailers, and watch Mission Impossible rogue nation "trailer 2" (same trailer as above). Audio is output PCM.
What makes you assume the iTunes Store sever's 2:25 AC3 5.1 encoded trailer is the same file as the Apple Trailer's server 2:29 AAC 2.0 DD ProLogic II encoded trailer?
Valid point: I did assume they were the same trailer/file.
You appear to be operating under the misconception that any DD5.1 bitstream connection between the TV4 and your AVR in the "Dolby Surround" output mode must a) be sourced from a Dolby encoded audio track and must b) contain 6 channels of audio. This is not true. If the source track is AAC mono, then the TV4 will, in the "Dolby Surround" mode, open a DD5.1 connection with your receiver but, under tvOS v9.0.1, will only "impress" the source center channel mono audio on the center channel of the DD5.1 bitstream. Since all other channels are "empty," the AVR then plays only the center "active" channel through your speaker system and thus plays the audio as it was originally encoded on the source AAC audio track.
In a similar manner, an AAC 2.0, stereo, or DD PL II audio track content will be "impressed" on the same DD5.1 connection as L and R audio along with four "empty" audio channels and only play back through your receiver's left and right front speakers. Further, since the DD5.1 connection tells your AVR the bitstream actually contains six discrete audio channels (four of which are "empty"), most receivers disable DD Digital PL II post processing capabilities and you are stuck with 2, and only 2, active channels playing back.
Yup. What my data demonstrated without your details.
That is why I recommend you use an TV4 app like "Computers" along with test videos containing both AAC and AC3 audio tracks to tabulate how the TV4 "Dolby Surround" setting outputs differently encoded audio tracks employing different forms of channelization. I can post some test clips containing various combinations of AAC and AC3 encoded tracks if needed for testing on your system.
Please do, I'd be most curious to see what I find.
Please do, I'd be most curious to see what I find.
http://downloads.walker4.me/Temporary_files/Test-1.m4v
The above file contains a segment of the recently re-released King Kong (1933) BD with both AAC mono and AC3 mono encoded audio tracks. It is keyed to auto-open with the AC3 track pre-selected to allow your AVR to "see" the actual source AC3 channel as encoded for the AC3 track when played using the TV4 "Dolby Surround" output connection mode. If you then switch to the AAC track for this test video clip, you AVR should indicate the TV4 device has switched to a DD5.1 bitstream connection which, if you listen to each individual speaker, only carries the single, center channel of "active" audio sourced from the AAC mono track.
http://downloads.walker4.me/Temporary_files/Test-2.m4v
The second test file is your Apple Trailers Mission: Impossible Rogue Nation trailer modified to include a secondary AC3 encoded audio track of the original Dolby Pro Logic II AAC audio data. Like the first test file, this clip is also keyed to open automatically with the AC3 track pre-selected in apps that allow this. In this case, your AVR should identify the AC3 track audio as a DD2.0 encoding. Since these two channels were originally encoded for Dolby Pro Logic II playback, if your receiver is automatically or manually set to perform DD PL II post-processing, the 2-channel audio should play back with additional center and surround speakers active. On the other hand, if you select the original AAC 2.0 DD PL II track for playback, your AVR will, once again, indicate the TV4 device is connected to your receiver using a DD5.1 bitstream connection but only be playing the AAC sourced audio as active stereo channels through your front L and R speakers.
http://downloads.walker4.me/Temporary_files/Test-3.m4v
The third test video is a clipping from Battleship. It contains an AAC DD PL II and DD5.1 audio tracks. Once again, the source AC3 track is flagged to auto-open in apps that are programmed for this. In this case, your AVR should indicate 6-channel decoding for both tracks but only the AC3 track actually contains six channels of active audio while the AAC track, like the Test-2 file, only plays in stereo. On my system the only way to tell the difference between the AAC sourced and DD5.1 sourced audio track is to listen to the speakers or check to see if my AVR's LFE "Activity" indicator lights periodically—i.e., AAC 1.0 and 2.0 sourced audio tracks never contain Low Frequency Effects activity.
Updating this thread
TVOS 9.1 and 9.1.1
At this point, setting Audio to Dolby Surround, either results in Dolby Digital if that format is output, or PCM if DD is not supported by app. From end user perspective, this is ideal.
atv4 some apps center speaker output missing Dolby Digital
