VC-1 Blu-ray rips stutter during playback with Plex app on Apple TV 4K (Gen 2)

[SimplePanda]

Server Version#: 1.28.1.6104
Player Version#: Current

It seems that there is a persistent issue with the 4K Apple TV playing back plain old HD VC-1 based MKV files.

The player appears to support Direct Play with these files (basically backups of my Blu-ray collection packaged as MKV) and for the most part playback does work fine.

However, periodically, the video just starts randomly stuttering / dropping frames and the audio and video come badly out of sync. This happens regardless of what audio format is playing (DTS-HD, DTS, PCM).

This can be instantly fixed with a tap of the back/forward button on the remote to skip playback back or forward by a single step (about 10-15s). The same stuttering/misplayed part of the stream begins playing again and works absolutely fine - so the issue is absolutely not in the playback stream or is related to the file data itself.

More importantly, if I use the Infuse 7 app on the exact same Apple TV 4K (A12 based) with the same Plex server on the same Synology NAS server playback of the same files is all flawless. There’s no transcoding on the Plex server, surround sound is perfect, etc - purely direct play.

I’ve found dozens of Reddit threads, etc all confirming what I’m seeing - VC-1 is basically broken on the Plex app for Apple TV and the only suggested workarounds are “use Infuse or transcode your VC-1 movies”, the latter of which is not an option as far as I’m concerned.

Is anyone else seeing this? Can anyone from the Plex confirm this is a known issue that is being worked on?

I can provide any logs/debugging data necessary to help narrow this down.

[ChuckPa]

Have an ATV 4K (2017 model)

No VC-1 issues . Player app is Direct Play

You recognize the movie?

[SimplePanda]

Possible a rate issue? I was watching Back to the Future and it stutters constantly, but plays back fine in Infuse on the Apple TV 4K (2020), as well as Infuse / iOS on my M1 Max and VLC (also M1 Max) playing direct from the MKV file (off the NAS).

The stated rate is BD level, so close to 38Mbps peak.

Possible the Plex app chokes / leaks at higher rates? Like I said - if you skip forward or back (10s or whatever the skip is) it plays fine again for a few minutes, then loses sync and stutters.

There’s a Reddit post with more than a few people echoing the same issue:

r/PleX - Plex + Apple TV 4K vs VC-1 Remuxes

Direct BD rip. No transcode. No issues with H.264 or MPEG-2 titles. No issues in other apps. Basically Plex on Apple TV + VC1 BD Rip is the reproducible problem.

[ChuckPa]

When you’re playing, and pull down to look at the “Technical Details”, what do you see ?

Is it DirectPlay or is it being transcoded by the server?

If the server is transcoding, check the player’s quality settings.

When I looked at the Reddit thread, they reference tvOS 15.5.
That one was problematic for me. I’m now on 15.6 and have no VC-1 issues.

Can you give me the name of any particular title which causes problems?
( I have a couple large boxes of discs and will go hunting .. or borrow it from one of my friends if I don’t have it )

[SimplePanda]

tvOS 15.6. Streaming all set same as yours - auto adjust off, home/internet streaming to max and audio original.

Back to The Future 1 - ripped from Blu-ray to MKV (MakeMKV 1.17.1 / ARM64).

[ChuckPa]

Gotcha on the title.

I will go find that one. I have several variants

[SimplePanda]

Great!

FYI when playing it to even slide down to get that photo for you, the “Universal” title card splash at the start immediately began stuttering. It also generally stutters again right around when the robot arm feeds Einstein.

Like I said if you skip back you can re-watch the sequence without stutter so the video bitstream itself is fine and -will- play on the ATV4k/A12 just fine; it just seems to routinely nosedive when left to play over time.

[ChuckPa]

I’ll keep an eye open for that. Thanks.

I just got the jewel cases and discs wiped off (a bit of dust) and am starting to rip now.
I knew which box these were in

[SimplePanda]

Awesome. For completeness my disc was from the “25th anniversary trilogy” release, though I’m not sure if they did different encodings for the collection vs. single releases (or if there were single releases).

[SimplePanda]

Also for absolutely completeness and to make sure all the bases are touched - the Apple TV 4K / A12 / 2020 in question is connected via gigabit ethernet to a Unifi switch in the entertainment rack, which is connected via gigabit to my core switch (another Unifi). The NAS is connected directly to that core switch via 10GbE (Synology DS1621+ w/ first party 10G card) and the Plex Media Server install on the DS1621+ is the latest version for Syno downloaded directly form plex.tv.

Other titles with similar bitrates but in other codes play without issue so it’s definitely not a network or storage performance problem.

[ChuckPa]

For all who are interested.

1. I ripped my BluRay

[chuck@glockner vc1.2004]$ mediainfo Back\ to\ the\ Future\ \[800\].mkv 
General
Unique ID                                : 18654229632225947138035453204298730900 (0xE08AC8795017FC6100D8CBDA7280D94)
Complete name                            : Back to the Future [800].mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 22.5 GiB
Duration                                 : 1 h 56 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 27.8 Mb/s
Movie name                               : Back to the Future
Encoded date                             : UTC 2022-08-18 17:55:46
Writing application                      : mkvmerge v70.0.0 ('Caught A Lite Sneeze') 64-bit
Writing library                          : libebml v1.4.2 + libmatroska v1.6.4
Cover                                    : No

2. The app shows
   

   

3. App Version 8.7 (3452)

4. Results so far
   – Direct Play
   – No issues back and forth but continuing to let it play.

[SimplePanda]

Ok - I’ve been doing some testing.

These all work for me, no issues (all discs MKV rips from my original Blu-ray copies):

• Samsara - 264 with DTS HD MA. No issues.
• Sunshine - 264 and DTS MA 5.1. Fine.
• Spinal Tap - 264 and DTS MA. Fine.
• Stargate - MPEG2 and DTS MA. fine.
• Ferris Bueller’s Day Off. 264 and TrueHD. Fine.
• Breakfast Club - 264 and DTS MA. Fine.

Skips/drops frames reliably:

• Back to the Future 25th Anniversary - 26.9 Mb/s VC1 with DTS HD MA.
• Natural Born Killers. 27.8 Mb/s VC1 with TrueHD (transcoded to FLAC on server).
• Baraka - 27.3 Mb/s VC1 with DTS HD MA.
• Serenity - 20.5 Mb/s VC1 with DTS MA 5.1.

Skips/drops frames but takes longer to manifest:

• Never Ending Story - 23.1 Mb/s VC1 with DTS HD.
• Goonies - 22.4 Mb/s VC1 with TrueHD (transcoded to FLAC on server).
• Weird Science - 29.8 Mb/s VC1 and DTS HD MA.

Some debugging:

I turned on the debug overlay in the Apple TV app. When the stutter happens, the Performance section’s A/V indcator (which typically hovers as close to 0.000 as it can) shoots up. I assume this is the sync indicator showing that A/V sync is now being lost. Additionally, the dropped frames indicator starts increasing by 18-20 per second. This tracks with the visual presentation of the stuttering - it looks like tons of badly dropped frames.

The movies that play fine (both the two VC1 titles that work fine and all the 264 titles) have 0 or 1 dropped frame total across ~10ish minutes of playback. The movies that stutter many many dropped frames within (typically) 5-10 minutes of playback. For me, Back to the Future starts dropping frames within the first 3 minutes.

Of course, VC-1 has “Hardware Decoding: no (videotoolbox)”. The AVC/264 movies are all “Hardware Decoding: videotoolbox (videotoolbox)” - so the CPU is being used for VC-1 (of course, as Apple TV doesn’t support VC-1 decoding).

I then enabled the logging/debugging in app, recreated the stutter in a VC1 movie, and downloaded the logs. Low and behold, I’ve got these lines:

2022/08/18 16:00:40.908 (521 MB) (7026346) ⚠️ PMKMPVClient.m:496 | [cplayer] warn: 
2022/08/18 16:00:40.908 (521 MB) (7026346) ⚠️ PMKMPVClient.m:496 | [cplayer] warn: Audio/Video desynchronisation detected! Possible reasons include too slow
2022/08/18 16:00:40.908 (521 MB) (7026346) ⚠️ PMKMPVClient.m:496 | [cplayer] warn: hardware, temporary CPU spikes, broken drivers, and broken files. Audio
2022/08/18 16:00:40.908 (521 MB) (7026346) ⚠️ PMKMPVClient.m:496 | [cplayer] warn: position will not match to the video (see A-V status field).
2022/08/18 16:00:40.908 (521 MB) (7026346) ⚠️ PMKMPVClient.m:496 | [cplayer] warn: 

I wondered, as my Apple TV is also used as a HomeKit hub for my house, if there may be random load on the system that the A12 can’t sustain along with VC1 decoding. This would explain why the stutters in playback never happen in the same place.

Unfortunately, disabling the hub functionality in that Apple TV didn’t resolve the issue.

So, working on the assumption that this is a CPU issue with Plex on the Apple TV 4K (2020) / A12, I tried the following:

• Infuse 7 app on the same Apple TV - Zero issues in any title. Uses Direct Play for audio and video.
• Infuse 7 app running my M1 Max MacBook Pro - Zero issues in any title. Uses Direct Play for audio and video.
• Plex app running on my M1 Max MacBook Pro - No issues (even though it’s the iPad app running unoptimized from the app store). Uses Direct Play for audio and video.
• PS5 Plex App - can’t properly test. Doesn’t support VC1 locally and has to offload/convert on server, which isn’t ideal.

So that’s where I’m at - the Plex app on Apple TV reliably drops frames while software decoding VC-1 titles. It feels like it’s a CPU related issue on the Apple TV, so I’m hoping there can be some bug fix to address it.

Unfortunately, it looks like @ChuckPa hasn’t been able to reproduce on his end. I’m wondering if it’s the 2020 variant of the Apple TV with the A12 (vs his A10X unit).

Either way, I’m currently stuck playing back VC-1 titles in Infuse, which performs well as a player but lacks the interface quality of Plex.

[ChuckPa]

Can you please send me, in our PM, the full AppleTV log?

Also, in our PM, please share the XML (media info specific only)

I will forward that to Engineering with a trouble ticket.

[DasLemo]

Just came here to say that I have the exact same behaviour with my VC-1 rips and I am happy to see that I’m not the only one seeing this problem. It’s a horrible experience watching these on my Apple TV and sadly exists since I got the Apple TV. Whenever I watch VC-1 rips I have to switch to the tizen smart TV app as there seems to be no stuttering.

[SimplePanda]

Have you heard anything from the iOS/Apple TV team @ChuckPa ?

[ShadowFM]

Hi all,
I would like to join the problem and report that it happened to me for the first time with “Iron Man”.
Video: VC1
Audio: DCA

[SimplePanda]

FYI this issue is still present with tvOS 16. VC1/DCA on a 4K 2nd Generation, same as previously reported; skipping and frame drops within minutes of starting a VC-1 Blu-ray rip.

[Hurin]

Been seeing this issue for months on certain VC-1 TV series Blu-Rays rips (The Office, most prominently). Apple TV only. Doesn’t happen on my Shield.

I googled it a few months ago and was reassured when I found others were experiencing it (wanted to see if it was something wrong with my stuff).

r/PleX - Apple TV stutter on high bitrate playback