Opened 14 months ago

Closed 12 hours ago

#13369 closed Bug Report - General (Works for me)

Playback issues with 30Hz display

Reported by: paulsd Owned by: mark-kendall
Priority: minor Milestone: 31.0
Component: MythTV - General Version: v29.1
Severity: medium Keywords:
Cc: Ticket locked: no

Description

I'm using MythTV 2:29.1+fixes.20180414.329c235-0ubuntu3 in Ubuntu 18.04.

I recently got a new 4K TV. This TV has one HDMI 2.0a port (which supports 4K@60Hz), and three HDMI 1.4 ports (which only support 4K@30Hz). If I connect my MythTV box to the HDMI 2.0a port and configure X to display at 4K@60Hz, then everything works fine. Unfortunately, only the HDMI 2.0a port on the TV supports ARC, so this port needs to be connected to my stereo system instead of my MythTV box. If I connect my MythTV box to an HDMI 1.4 port and configure X to display at 1K@60Hz, then everything works fine.

However, if I connect my MythTV box to an HDMI 1.4 port and configure X to display at 4K@30Hz, then Recordings work fine, but LiveTV playback doesn't work. Specifically, LiveTV video is played at half speed, and only brief clips of audio are occasionally played. The same symptom occurs using any of the accelerated Playback Profiles (my system only supports OpenGL and VAAPI, so I can't test VDPAU). LiveTV plays at half speed even if audio is disabled (by setting the 'Audio output device' to NULL in the frontend settings).

If I use a non-accelerated Playback Profile at 4K@30Hz, then LiveTV plays properly, but I have other problems (video tearing and high CPU usage). In addition, if audio is disabled (by setting the 'Audio output device' to NULL in the frontend settings), then LiveTV still works as expected, but Recordings play back at double speed.

So, something is clearly different about the display refresh rate handling for LiveTV vs Recordings, and both are wrong in some cases.

Attachments (1)

mythtv_logs.tar.bz2 (72.1 KB) - added by paulsd 14 months ago.
Tarball containing mythtv -v playback logs for many permutations of settings

Download all attachments as: .zip

Change History (6)

Changed 14 months ago by paulsd

Attachment: mythtv_logs.tar.bz2 added

Tarball containing mythtv -v playback logs for many permutations of settings

comment:1 Changed 14 months ago by paulsd

In the log tarball, mythtv_logs/30hz_opengl_noaudio_live.log and mythtv_logs/30hz_opengl_audio_live.log show half-speed (30fps vs 60fps) video playback, and mythtv_logs/30hz_noopengl_noaudio_rec.log shows double-speed (120fps vs 60fps) video playback. The other logs all played back at the expected speed (60fps).

I also stumbled across https://forum.mythtv.org/viewtopic.php?t=1220 which looks like another report of this same issue.

Version 0, edited 14 months ago by paulsd (next)

comment:2 Changed 11 months ago by Peter Bennett

Owner: set to Peter Bennett
Status: newassigned

comment:3 Changed 11 months ago by Peter Bennett

I am unable to recreate this with v29 or latest master. I tried OpenGL slim. Live TV as well as recordings play fine on a 4K display with an HDMI 1.4 running at 30HZ 3840x2160.

Is this interlaced content? Check your deinterlacer - I was using Linear blend.

Try pressing pause while in Live TV for a few seconds, then unpause.

There is a fix for the pause-unpause issue fix in v30.

comment:4 Changed 3 weeks ago by mark-kendall

Owner: changed from Peter Bennett to mark-kendall

comment:5 Changed 12 hours ago by mark-kendall

Milestone: needs_triage31.0
Resolution: Works for me
Status: assignedclosed

Testing with master and v31 this appears to be working properly.

Note: with the new A/V sync code, the display refresh rate is effectively irrelevant - apart from deciding which deinterlacer to use. The new code implicitly syncs to the current refresh rate and will drop frames as needed.

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