Channel switching does not work on Cubox since 7.0.2

pajtaz · July 11, 2017 at 2:42 PM

Hello,

I have been testing every single build since 7.0.2 and on every single build I have the same problem. I was expecting the issue to be fixed in LibreELEC 8.0.2 but the same issue is still there.

I am using Tvheadend as client and Tvheadend 4.2 as PVR backend. I have a Cubox-i4x4 running kernel version 3.14 of LibreELEC. On the 7.0.2 version (with kernel 3.14) live TV is perfect. Channels tune with little delay, picture is perfect, audio is perfect, deinterlacing is perfect. In the issues below I have the EXACT same hardware.

On LibreELEC 8.0.2 and all builds from 7.90.001, live TV is basically unusable. I started with clean installations so the issue is not with upgrading. I set up Tvheadend in the same way, all other settings for playback and system same as 7.0.2. Once I go to TV, I tune to any channel and channel plays after a bit of buffering (longer than 7.0.2 but reasonable). Then I switch to another channel, the buffering starts, goes to 100% really slowly (10 seconds), nothing happens, buffering starts again to 100%, nothing happens, and so on. I have to stop playback. Then I try it again (start playback of a channel, try to switch) and same thing happens.

I played with audio settings, video settings, deinterlace settings, etc. but nothing helps. I want to mention that on Tvheadend side, there are no errors so the issue is with Kodi. Something changed drastically from 7.0.2 that makes watching live TV unusable on my Cubox. I am not sure if anyone else is having the same issue.

I can post logs if anyone wants to see them but for that I have to switch SD cards and annoy my wife. For now, maybe someone can tell me what's wrong with information above. To repeat, this happens on EVERY single build since 7.0.2 on Cubox. I am currently continuing to use 7.0.2 and cannot use any LibreELEC since then due to this problem.

**chewitt** · July 11, 2017 at 9:14 PM Official Post

Kodi Krypton uses a completely different video caching process to older Jarvis releases. The positive of this is that untold playback gremlins are resolved and the codebase is considerably cleaner. The negative is that caching takes a lot longer and this impacts the channel zap speed. There is basically nothing you (or we) can do without reverting/modifying very large chunks of code; which probably breaks more than it fixes. The issue has been communicated at loud volume and with crystal clarity to the required Kodi developers and Kodi Leia should make a great leap forwards (or backwards, depending on your point of view) for this issue. Leia is tentatively scheduled towards year end.

pajtaz · July 12, 2017 at 7:09 AM

This "bug" is not about channel zap speed. The channel never switches. It does not seem to be an issue about caching since live TV switching works fine on my Windows 7 Kodi Krypton (any version) using the exact same setup (the only thing being different is imx6 vs Windows versions of Kodi). I could be wrong, maybe caching is causing this issue for Cubox specifically. Whatever the issue is, it seems to be specific to Cubox versions of Kodi or Tvheadend PVR client.

**kszaq** · July 12, 2017 at 7:53 AM

I have no idea about Cubox code but the same bug appeared in my Amlogic builds when I improperly implemented codec drain - on channel switch hardware decoder stalled trying to drain codec.

pajtaz · July 12, 2017 at 10:16 AM

Where in the code is this? Sounds like the same problem.

**kszaq** · July 12, 2017 at 11:00 AM

pajtaz Decode() should return VC_BUFFER when decoder is drained. I would say this piece of code needs an additional check: xbmc/DVDVideoCodecIMX.cpp at Krypton · xbmc/xbmc · GitHub

But as I said before - I have no idea about iMX code.

pajtaz · July 12, 2017 at 11:52 AM

Thank you. It seems the decoder was completely rewritten in Krypton for iMX. This will be a nightmare to understand.

**vpeter** · July 12, 2017 at 2:55 PM

Don't worry: In Leia will be rewritten again

**vpeter** · July 13, 2017 at 10:56 AM

kszaq, you have any tip how to improve this part of the code?

**kszaq** · July 13, 2017 at 1:28 PM

vpeter In Amlogic decoder queue size won't go down to zero, especially when switching channels. I implemented a workaround (inspired by AMC in Kodi) to return VC_BUFFER when the queue size is not changed for 1 second: LibreELEC.tv/kodi-le-028-aml-Implement-drain.patch at libreelec-8.0-sX05 · kszaq/LibreELEC.tv · GitHub

pajtaz · July 22, 2017 at 11:58 AM

Any progress on this?

**vpeter** · July 22, 2017 at 12:17 PM

No progress.

I got back my DVB-T stick to test this myself. Sadly I have to confirm that whole PVR thing doesn't work very well. Actually it was much worse that what I expect. Basically PVR is unusable for me. But didn't test LE v7 to compare.