On 12.07.2013 23:54, Ulrich Spörlein wrote:
I'm trying to setup XBMC on a -CURRENT box with an IvyBridge CPU and
GPU. While testing playback via mplayer on a LG TV over HDMI, I noticed
that sound is lagging video by about 100-200ms or so. When I switch to
using the jack outputs powered by some Realtek chip, audio is perfectly
fine.
Is HDMI lag a known problem? Can this be fixed?
root@coyote:~# dmesg | egrep vgapci\|pcm
vgapci0: <VGA-compatible display> port 0x3000-0x303f mem
0xe0000000-0xe03fffff,0xc0000000-0xdfffffff irq 16 at device 2.0 on pci0
agp0: <IvyBridge mobile GT2 IG> on vgapci0
pcm0: <Realtek ALC888 (Rear Analog)> at nid 20 and 24 on hdaa0
pcm1: <Realtek ALC888 (Rear Digital)> at nid 30 and 31 on hdaa0
pcm2: <Intel Panther Point (HDMI/DP 8ch)> at nid 6 on hdaa1
pcm3: <Intel Panther Point (HDMI/DP 8ch)> at nid 7 on hdaa1
drmn0: <Intel IvyBridge (M)> on vgapci0
I don't know what to say. I am now using HDMI audio from NVIDIA card to
quite old external 5.1 receiver with XBMC every day, and I haven't
noticed lags. Before that I've also successfully used SPDIF connection
for the long time. Though I've never specially tested it somehow other
then watching movies. :) If you have some good testing methodology --
please, welcome to share. By the HDA driver HDMI is handled exactly the
same way as analog output from the point of data buffering, so I would
not expect there major differences.
You may try to experiment with hw.snd.latency sysctl to tune buffering
in kernel to see whether it affect the result.
Also you may compare delays when doing AC3/DTS pass-through with case of
software decoding and discrete (multichannel) PCM playback.
The only potentially related effect I have noticed is that my receiver
eats first second or about that of playback stream. It makes short
sounds like GUI event notifications inaudible sometimes. I guess that
could be made to restore audio sync after some unavoidable startup
delay, but that is only my guess.
--
Alexander Motin
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