https://bugs.freedesktop.org/show_bug.cgi?id=64503
--- Comment #14 from Andy Furniss adf.lists@gmail.com --- (In reply to comment #0)
(originally reported to Fedora: https://bugzilla.redhat.com/show_bug.cgi?id=954009)
I've recently started trying out 24 Hz again as my TV handles it better, and XBMC is finally at a point where they can keep things synced up when playing at exactly the monitor refresh rate.
Unfortunately that broke the HDMI audio output. If I try to output audio when the refresh rate is at 24 Hz, the receiver will lose audio sync every few minutes, resulting in silence until it regains sync.
I've tried the following:
- Sending audio over SPDIF from the onboard audio to the same receiver
works fine. Another cable though, and cannot handle high-bitrate formats, so hardly a long term solution.
- Audio format doesn't seem to matter. I get glitches with PCM, AC3 and
DTS. DTS is the worst, but that might just be because it requires more effort to sync back up again.
- It's not xbmc that gets confused as sending audio from an entirely
different program results in the same audio glitches (I tried mplayer with -vo null in the background).
- Doesn't seem to be a application buffering issue as I see no spikes in
either xbmc's or mplayer's sync statistics when the glitch appears.
This is with kernel-3.8.7-201.fc18.x86_64.
Well I guess my bare bones LFS setup is very different to fedora, but I can't reproduce this.
Kernel drm-next recent-ish with radeon HD4890. Can only test PCM into TV with mplayer + alsa (pulse not installed)
cpufreq set to performance, GPU on low. TV screen set below monitor screen.
Tried 11 minute 44.1k CD track and 20 mins of blu-ray -vo vdpau 48k stereo and didn't hear any glitches at all. Of course blu-ray was 23.976 and modeline was 24, but I doubt that's relevant, mplayer will tweak video rate to keep audio sync and -framedrop was given.
FWIW this is my 24Hz line as shown by xrandr --verbose, maybe yours is different?
1920x1080 (0x2cd) 74.2MHz +HSync +VSync h: width 1920 start 2558 end 2602 total 2750 skew 0 clock 27.0KHz v: height 1080 start 1084 end 1089 total 1125 clock 24.0Hz
Having never used pulse I don't know if it's easy to bypass (assuming you are using it),
mplayer -ao alsa:device=hw=1.3 may work (assumes cat /proc/asound/cards shows HDMI as 1)