Bugzilla – Bug 16287
Avoid use of pcm_route ALSA plugin for Fab4
Last modified: 2011-05-09 09:41:36 UTC
Testing had revealed that use of the ALSA pcm_route plugin adds some significant CPU overhead in the output path. The existing "hifi" configuration is based of the examples from the ALSA documentation. Experimentation suggests that a simpler plugin chain will work just as well for our purposes.
== Auto-comment from SVN commit #8844 to the jive repo by ayoung == == http://svn.slimdevices.com/jive?view=revision&revision=8844 == bug 16287: Avoid use of pcm_route ALSA plugin for Fab4 Change default ALSA configuration to use a setup that avoids including the pcm_route plugin in the chain.
Assign to QA for verification testing. The main thing to check is bit-perfect output from the digital outputs. John, would you be prepared to look at this?
Sure, I'd be glad to try it out. I tried to look at the new file but svn was running excruciatingly slow, I'll have to try it tonight. John S.
I tried the new file and it does work, it plays music fine. I tried to run my usual bit perfectness tests but something strange seems to be happening. This records the S/PDIF stream with another device and then compares the files. It does a good job of aligning the files. Normally this works very well and can find single bit differences. With this output not only did it say there are differences but they are major. This is probably a problem in the test setup rather than any problem with the ALSA configuration. I'll have to do some more experimenting with this. One thing I can try is running the tests with the original alsa file and with the new one. If THAT comes out the same then there is a good probability the new config is bit perfect. John S.
I finally got the test methodology working correctly. The new ALSA config is definitely bit perfect. So far it works fine, I haven't found any issues with it. John S.