On 08/12/2010 04:47 PM, Elvis Dowson wrote:
Hi Eric, I came across an old thread, http://www.ruby-forum.com/topic/107228"There is a general issue related to the fact that when using usrp_wfm_rcv and similar applications that there are in fact two clock domains, and that they are guaranteed not to match. There's an osc on the USRP and an osc associated with the sound card. We made an API change in the audio interfaces that can specify that it's NOT OK to block when accessing the audio interface. When used in a flow graph that contained both an audio sink or source and a USRP sink or source, this would result in the USRP being the master clock, and would dodge the "two clocks" problem. Although the parameter was added to all (most) audio interfaces, I believe that it currently only works on the portaudio interface. Please feel free to fix this for gr-audio-alsa, gr-audio-oss and gr-audio-osx." This could potentially explain the issue I have, with distorted and crackling audio. It might also explain the nearly un-reproduceable random behaviour when it sometimes works giving clear audio output (so far has happened only 4 times in 6 weeks, approx 16 hours a day). How would one go about fixing this for gr-audio-alsa? Perhaps if you can give me some high level tips and pointers, I could try to make the changes.
Depending on how ALSA is configured, it may be able to do the final resample internally. I'd look carefully at the sample rates at each of the blocks and see what rate is being sent to ALSA. Drawing this out should be helpful.
Philip _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
