I was starting to think I was going crazy. Hate to have issues but glad I’m not the only one. Blend made no difference here either.
I can also confirm that there is major studdering with mpeg2 channels after upgrading to tvOS 11. It was evident last night during the Thursday night football game as well as watching any news channel with a ticker/scrolling bar across the bottom.
This occurring on both 1080i and 720p channels. This is happening within VLC as well.
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Took a chance an upgraded one ATV and also seeing stuttering. Seems more noticeable with 1080i channels but is also there with 720p. Perhaps the deinterlacer doesn’t get along well with TvOS11?
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I also am seeing the stuttering problem after upgrading to tvOS 11. It appears to happen approximately every second, very evident on news tickers and fast panning shots. Doesn’t matter if it is live TV or a recording.
I have 2 ATV4 boxes,and I only upgraded one of them. The other one is still on tvOS 10, and I don’t see any evidence of stuttering on that box.
I also tried changing the deinterlacing mode to blend, and that seems to have more obvious stuttering.
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I also have this stuttering on IOS11 in the UK.
Other ATV on IOS 10 plays perfectly, this is the same problem i had in the early days of the UK DVR beta it took a while to iron out the problems.
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I was able to reproduce this issue with the NHL game recording that @turtletank sent me. The recording was very high bitrate (18mbps), and produces a hiccup every ~5s where some frames are dropped and video jumps ahead slightly.
I downgraded to tvOS 10.2.2 (using this ipsw) and the issue went away.
On tvOS 10, Channels requires about 80% CPU to playback high-bitrate mpeg2. This is pretty high, but still leaves enough room for the OS and UI to function. If you’re just watching TV with no UI, tvOS 10 plays back without any frame drop issues. (Still, if you pull down the quick guide on tvOS 10 and swipe left/right quickly you can see the video in the background struggles and drops some frames because there’s not a lot of headroom).
On tvOS 11, for some reason the CPU usage during playback of mpeg2 is 100-110%. This is using the exact same test recording, and the same build of Channels with the exact same code on the same hardware. This means that something within tvOS itself has been changed which is affecting the CPU resources available to our app. With CPU usage so high, there’s barely any headroom on the system and it will periodically fall behind and has to compensate by dropping some frames.
The InstaTV and VLC apps use the exact same mpeg2 software-decoder as Channels, which explains why all three apps are now seeing this issue after upgrading to tvOS 11. This issue also only affects the 2015 Apple TV 4. The Apple TV 4K works just fine on tvOS 11, since it has a much more powerful CPU which can decode high-bitrate mpeg2 without breaking a sweat.
I’m looking into workarounds that would let us get back the performance we saw on tvOS 10…
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If you're hitting this issue, it might be worth downgrading to tvOS 10 while Apple still lets you: http://appldnld.apple.com/tvos10.2.2/091-23452-20170720-5D53229C-6A56-11E7-8577-8B2C4A4DD6D5/AppleTV5,3_10.2.2_14W756_Restore.ipsw
The difference in CPU usage between the two OS versions is astounding. I'm still not sure what they did to cause such a big performance drop.
tvOS 10:
tvOS 11:
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This seems like a better solution than transcoding instead which has been a bit of a struggle on Windows. Thanks for the link!
I’m not seeing any stuttering on the UK MPEG2 channels. I assume since they are all SD that they aren’t high enough bit rate to be affected by the CPU bottleneck? (All UK HD channels are H.264.)
I can definitely confirm that there is stuttering on all HD channels in the UK.
It seems pretty intermittent but when it is there it makes the show unwatchable .
Here’s hoping this can be fixed.
Very strange. I have no stuttering on any channel, MPEG2 or H.264, SD or HD. I’m using the latest Channels beta, 9.23.707.
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The way I understand the issue, it has to do with bitrate which makes sense to me why some stations have problems and others do not. I’m beginning to watch the bitrate from the HDHR Prime and indeed those with lower bitrate are not causing much of an issue. In my area, all channels are different and your cable co. may also manipulate the bitrate/format which makes it difficult to say its a problem with a specific channel or not.
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This problem has been going on since the early days of tvOS 11 beta I was hoping that Apple would have ironed out the problems by now as it looks like a few other apps are having problems also.
The cpu issues I detailed above are specific to high-bit rate mpeg2. H264 uses hardware decoding and should not be affected.
If you’re seeing problems in the UK, send me a sample as detailed above. I only received one from @Valentine13 but that one played fine on my ATV4. Also make sure you are using v2.1.39
FYI, I installed V 9.12.204 and I’ve no stuttering anymore.
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Thanks @Valentine13, that helps narrow things down. I took another look at your sample and I see it’s using an uncommon feature of H264 which is triggering an edge-case. I will work on a fix.
Thanks for posting. Didn’t realize I had auto update set and had one ATV4 upgrade to tvOS 11. Did notice some slight stuttering (primarily on scrolling tickers) hence I decided to downgrade. What an odyssey followed.
First, I wanted to take some screenshots on the ATV. Found my USB-C cord ordered last year (just in case 
) and went to Xcode to take screen shots…ha!ha!..found I had to upgrade Xcode…then found I had to upgrade to Sierra. After several upgrade failures, finally got Sierra, then Xcode…screenshots taken. Then downgrade to tvOS 10.
Now, I’m loading all of my tvOS apps to replicate prior status. It’s been a pita, but I was glad to still be able to downgrade.
Thanks to all for the warnings and tvOS 11 feedback on ATV4…might not have caught this in time as we are still digging out from Irma. These forums and contributors (especially @Scott) saved our stellar experience on Channels.
I also have the stuttering described above after upgrading to tvOS 11.
New TestFlight build is available which fixes some remaining issues with H264 decoding.
No change to mpeg2 decoding yet. We’re trying to get in touch with Apple about the issue.
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Interestingly my system auto updated to tvOS 11 (64 GB) on my Apple TV, and so far so good. Recoding from MPEG-2 streams, wired internet, and haven’t tested 1080i input yet.