[mythtv-users] Slow skipping fwd-back with 0.19 -- USB audio to blame?

Chris Vargas ceenvee at yahoo.com
Wed Apr 5 17:17:55 UTC 2006


I recently upgraded my combo front/backend, and a
remote frontend, to 0.19.

Since the upgrade, I noticed that on my combo
front/backend, skipping forward and back was not
nearly as quick as it was under 0.18.1. If I
30-second-skip through a commercial block, then
5-sec-skip back a few times due to overshooting the
block ending, it can take over 5 seconds for the video
to start playing at the right speed and for the audio
to catch up to the video (you can hear it playing the
audio at the various skip points). This is on standard
definition MPEG2 recordings from a PVR-250 or -350,
not HD.

The remote frontend, on the other hand, skips forward
and back just fine: playback begins immediately.

Running mythfrontend with the "-v all" option on the
front/backend machine showed many many lines like the
following that seemed to correspond to skipping
forward/back:

2006-04-03 18:06:50.372 audio waiting for buffer to
fill: have 1536 want 4096
2006-04-03 18:06:50.380 audio waiting for buffer to
fill: have 2048 want 4096
2006-04-03 18:06:50.385 audio waiting for buffer to
fill: have 3072 want 4096
2006-04-03 18:06:50.395 audio waiting for buffer to
fill: have 1024 want 4096
2006-04-03 18:06:50.400 audio waiting for buffer to
fill: have 3072 want 4096
2006-04-03 18:06:50.404 audio waiting for buffer to
fill: have 3072 want 4096

Running mythfrontend with the "-v playback" option on
the combo front/backend also resulted in the following
logged messages, again, line after line of them
corresponding to skips:

2006-04-04 19:58:36.577 NVP: Audio is 28.2815 frames
ahead of video, doubling video frame interval.
2006-04-04 19:58:36.644 NVP: Audio is 30 frames ahead
of video, doubling video frame interval.
2006-04-04 19:58:36.711 NVP: Audio is 30 frames ahead
of video, doubling video frame interval.
2006-04-04 19:58:36.778 NVP: Audio is 30 frames ahead
of video, doubling video frame interval. 

I do not get multiple lines of that message when I use
"-v playback" on my remote frontend.

DMA is enabled on the front/backend machine. Setting
the "extra sound buffering" option in Playback did not
help. Searching mythtv-users for the above messages
didn't turn up any (to me) obvious solutions.

One possibility is the fact that I am using as my
sound output an external USB device (the Creative Labs
MP3+) for AC3 output to my receiver. A KnoppMyth forum
poster suggested there may be a problem with 0.19 and
USB audio. Could this problem result in this behavior?
How can I further troubleshoot or, hopefully, fix this
problem?

Thanks.


More information about the mythtv-users mailing list