Struggling with media playback sync

[MichaelD]

Hi, 

I'm hoping you can help resolve an issue I have syncing video playback across 2 Raspis. The same video file plays perfectly well on the player, but stutters and eventually stops on the remote. I'm a bit confused with how to enable/disable unicast, as some posts on the forum recommend this as a potential solution - can anyone give me a clue with this? I'm a complete newbie.

Thanks in advance, 
MD

[CaptainMurdoch]

For each FPP Remote listed on the the FPP MultiSync config screen, you should see a checkbox beside the Remote's IP address with the text "Select IPs for Unicast Sync".  Check the checkbox to enable unicast MultiSync to that Remote.  If you do not have any other Remotes or all Remotes are setup as unicast, then you should also open the "More Settings" section at the bottom of the page and uncheck the "Send MultiSync to ALL remotes via Multicast" and "Send MultiSync to ALL remotes via Broadcast" checkboxes.

[MichaelD]

Hi Chris,

Thanks, this is helpful. There is a checkbox next to the remote in the list, which I have checked. There's a checkbox below the list labelled 'Send MultiSync packets' which I also have checked. And there's a checkbox in the 'more settings' dropdown labelled 'Send MultiSync to ALL remotes via Multicast' that I have unchecked. It still doesn't playback smoothly. Am I doing it correctly? What else can I try to make this work?

Thanks in advance,
MD

[MikeKrebs]

What does your remote input config look like?
What does your remote output config look like?
Is it doing anything but playing video?

[MichaelD]

Hi Mike, 
Thanks for the questions. The system isn't doing anything except play video, and there's nothing else connected. No other interfaces or hats. I've not done anything to the input or output config settings, so presumably they are at default settings. See the screenshots below. Thanks in advance for any advice!

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[CaptainMurdoch]

Check the 'fppd.log' file for errors.  It shouldn't be stopping playback even if it goes out of sync.  In the FPP File Manager screen, look at the Logs tab and view the fppd.log file after trying to play the video and see if any errors are reported.  If none are, you could also try putting the Remote into Player mode and playing the video by itself and see if the video plays correctly.  Perhaps the file was corrupted somehow or this system has an issue playing it.

[MichaelD]

Hi Chris, 

Thanks for this advice, which is very helpful. I'm looking at the log, and I don't know what it's supposed to look like, but it doesn't seem to be reporting anything that looks like an error. 

I've swapped the player and remote and the same issue occurs. This rules out the file (which plays perfectly well in player mode on either unit) or the SD. 

I'm exporting my video from Blender, are there any particular compression settings that FPP favours? I'm using 640p, 60fps, h264, at super-low quality. I was led to believe it'd play 1920p.  I think this is a red herring too though, since it plays perfectly well in player mode.

I read somewhere about increasing the streaming cache for VLC (not in use in a FPP context) so is that something worth pursuing? 

Thanks to the community for helping to troubleshoot this issue. 

Speak soon, m

[CaptainMurdoch]

On the Remote, in the FPP settings page, go to the Logging tab and set the MediaOut and Sync options to Debug and then replay the file in Player/Remote mode and then look at the fppd.log file on the Remote when the file stops playing.  Cut and paste the last 20 or so lines here and we'll take a look to see if that helps any.  Please wrap the pasted lines in the 'code' tag.  In the post editor, the code option is the scroll which is the middle item in the 3rd box of icons from the right.

[MichaelD]

Hi Chris,
Thanks for these very clear instructions - it's helpful from my perspective as a beginner. Looking at the debug log, it does represent what's happening during playback. Lots of lost frames, then overreacting to compensate. Does this help diagnose the problem?
Thanks, MD

2024-02-06 09:12:32.477 (1844) [Sync] /opt/fpp/src/MultiSync.cpp:2426: ProcessSyncPacket()   filename: 0001-3000-640p-h264-60fps.mp4    type: 2   filetype: 1   frameNumber: 0   secondsElapsed: 47.51
2024-02-06 09:12:32.477 (1844) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:565: Diff: -228    SpeedUp  1.040/1.000 [goal/current]
2024-02-06 09:12:32.477 (1844) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:604: Diff: -228    libvlc_media_player_set_rate    (1.040)
2024-02-06 09:12:32.601 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 465 ms)
2024-02-06 09:12:32.601 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 449 ms)
2024-02-06 09:12:32.601 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 434 ms)
2024-02-06 09:12:32.602 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 418 ms)
2024-02-06 09:12:32.602 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 402 ms)
2024-02-06 09:12:32.602 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 386 ms)
2024-02-06 09:12:32.602 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 370 ms)
2024-02-06 09:12:32.602 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 354 ms)
2024-02-06 09:12:32.603 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 339 ms)
2024-02-06 09:12:32.603 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 323 ms)
2024-02-06 09:12:32.603 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 307 ms)
2024-02-06 09:12:32.603 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 291 ms)
2024-02-06 09:12:32.606 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 278 ms)
2024-02-06 09:12:32.606 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 262 ms)
2024-02-06 09:12:32.610 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 249 ms)
2024-02-06 09:12:32.621 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 245 ms)
2024-02-06 09:12:32.621 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 229 ms)
2024-02-06 09:12:32.625 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 217 ms)
2024-02-06 09:12:32.625 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 201 ms)
2024-02-06 09:12:32.629 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 189 ms)
2024-02-06 09:12:32.636 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 180 ms)
2024-02-06 09:12:32.640 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 168 ms)
2024-02-06 09:12:32.640 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 152 ms)
2024-02-06 09:12:32.644 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 139 ms)
2024-02-06 09:12:32.648 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 127 ms)
2024-02-06 09:12:32.659 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 123 ms)
2024-02-06 09:12:32.659 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 107 ms)
2024-02-06 09:12:32.663 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 95 ms)
2024-02-06 09:12:32.663 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 79 ms)
2024-02-06 09:12:32.667 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 67 ms)
2024-02-06 09:12:32.674 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 58 ms)
2024-02-06 09:12:32.675 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 42 ms)
2024-02-06 09:12:32.682 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 33 ms)
2024-02-06 09:12:32.682 (2616) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:116: picture is too late to be displayed (missing 17 ms)
2024-02-06 09:12:32.971 (1844) [Sync] /opt/fpp/src/MultiSync.cpp:2426: ProcessSyncPacket()   filename: 0001-3000-640p-h264-60fps.mp4    type: 2   filetype: 1   frameNumber: 0   secondsElapsed: 48.00
2024-02-06 09:12:32.971 (1844) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:482: Diff: 1708    Flipped, reset speed to normal    (1.000)
2024-02-06 09:12:33.478 (1844) [Sync] /opt/fpp/src/MultiSync.cpp:2426: ProcessSyncPacket()   filename: 0001-3000-640p-h264-60fps.mp4    type: 2   filetype: 1   frameNumber: 0   secondsElapsed: 48.51
2024-02-06 09:12:33.478 (1844) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:570: Diff: 1493    SlowDown 0.817/1.000 [goal/current]
2024-02-06 09:12:33.478 (1844) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:604: Diff: 1493    libvlc_media_player_set_rate    (0.817)
2024-02-06 09:12:33.971 (1844) [Sync] /opt/fpp/src/MultiSync.cpp:2426: ProcessSyncPacket()   filename: 0001-3000-640p-h264-60fps.mp4    type: 2   filetype: 1   frameNumber: 0   secondsElapsed: 49.00
2024-02-06 09:12:34.479 (1844) [Sync] /opt/fpp/src/MultiSync.cpp:2426: ProcessSyncPacket()   filename: 0001-3000-640p-h264-60fps.mp4    type: 2   filetype: 1   frameNumber: 0   secondsElapsed: 49.51
2024-02-06 09:12:34.479 (1844) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:565: Diff: 492    SpeedUp  0.902/0.817 [goal/current]
2024-02-06 09:12:34.487 (1844) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:604: Diff: 492    libvlc_media_player_set_rate    (0.902)
2024-02-06 09:12:34.972 (1844) [Sync] /opt/fpp/src/MultiSync.cpp:2426: ProcessSyncPacket()   filename: 0001-3000-640p-h264-60fps.mp4    type: 2   filetype: 1   frameNumber: 0   secondsElapsed: 50.00
2024-02-06 09:12:34.973 (1844) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:503: Diff: 0    Very close, use normal rate    (1.000)
2024-02-06 09:12:35.033 (1844) [Sync] /opt/fpp/src/MultiSync.cpp:2426: ProcessSyncPacket()   filename: 0001-3000-640p-h264-60fps.mp4    type: 2   filetype: 1   frameNumber: 0   secondsElapsed: 49.98
2024-02-06 09:12:35.046 (1844) [Sync] /opt/fpp/src/MultiSync.cpp:2426: ProcessSyncPacket()   filename: 0001-3000-640p-h264-60fps.mp4    type: 2   filetype: 1   frameNumber: 0   secondsElapsed: 50.00
2024-02-06 09:12:35.049 (1844) [Sync] /opt/fpp/src/MultiSync.cpp:2426: ProcessSyncPacket()   filename: 0001-3000-640p-h264-60fps.mp4    type: 1   filetype: 1   frameNumber: 0   secondsElapsed: 0.00
2024-02-06 09:12:35.050 (1844) [Sync] /opt/fpp/src/MultiSync.cpp:2389: StopSyncedMedia(0001-3000-640p-h264-60fps.mp4)
2024-02-06 09:12:35.050 (1844) [Sync] /opt/fpp/src/MultiSync.cpp:2396: Stopping synced media: 0001-3000-640p-h264-60fps.mp4
2024-02-06 09:12:35.050 (1844) [MediaOut] /opt/fpp/src/mediaoutput/mediaoutput.cpp:393: CloseMediaOutput()
2024-02-06 09:12:35.050 (1844) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:421: VLCOutput::Close() 50.000
2024-02-06 09:12:35.050 (1844) [MediaOut] /opt/fpp/src/mediaoutput/VLCOut.cpp:355: VLCOutput::Stop(166140) 50.000
2024-02-06 09:12:35.053 (1844) [MediaOut] /opt/fpp/src/mediaoutput/MediaOutputBase.cpp:35: MediaOutputBase::~MediaOutputBase()
2024-02-06 09:12:35.054 (1844) [MediaOut] /opt/fpp/src/mediaoutput/MediaOutputBase.cpp:67: MediaOutputBase::Close

[MichaelD]

Hi Chris / all, 

It's gone quiet on this thread so I'm wondering if we've reached the end point of the diagnosis and need to move on to raising a bug fix request? I don't know the procedure for that, so please advise. 

It's a shame - it seems that FPP doesn't reliably have this functionality since the 'upgrade' to VLC under the bonnet. I'd love to know of any alternatives that might do the trick.

Thanks in advance, MD

[CaptainMurdoch]

Sorry, threads get lost sometimes.  Is this video file something you can put somewhere and send us the link so we can try to reproduce the problem ourselves?  You don't have to post the URL, a direct message is fine.

[MichaelD]

Hi Chris, 
Thanks for picking up this thread again. I'll send the video file via DM but the problem seems to be the same regardless of the file. If there's a test video file available that definitely works on your set up, please feel free to send it over so I can try it out and see whether there are any differences with mine.
Thanks, speak soon, 
MD

[TomsLEDs]

Would really like to see the solution when you guys get it resolved. I am planning to set up my show this year in the same manner.

[CaptainMurdoch]

We exchanged some direct messages and he was able to get it somewhat working.  The test file I sent him did not have the same issue originally described.  I believe he is currently testing a few different things including checking if the issue is due to the fact that his original files don't have an audio track.  Hopefully he will have some results to report back soon.

[MichaelD]

Hi, 

Thanks all for the assistance in making progress with this project. The issue causing the problem was the data rate of the video file, combined with the lack of a soundtrack. I'm in the process of testing to try and figure out which is the main culprit, but for now, if your video isn't working, try rendering out with a (silent) sound track on the video file. 
The playback on the remote has been most reliable with the data rate circa 2000kbps, but I have no idea whether this would be dependent on the type of video material you are using (ie, how much movement, number of colours etc).

Best of luck with your projects!
Speak soon, MD