> Noah Beck wrote: >> [...] >> and then ran 100 times. In the first 67 recordings, I got 6 occurrences of >> a recording with the tinny sound at the beginning, and in each of those, >> after 5 seconds the sound returns to normal. Furthermore, for all of the >> other 61 recordings that sounded fine, they sounded fine all the way >> through. So, --set-audio-input=1 initiated after the recording starts, >> appears to put the driver into the non-tinny state if it is tinny, and >> doesn't cause a problem if the driver was already in the non-tinny state. >> I added set-audio-input to my channel-change script for now. I placed one >> of the 6 tinny+workaround recordings at: >> >> http://roonabeck.bellsofireland.com/file65.mpg >> >> The first 5 seconds sound tinny, and the next 5 seconds sound fine. >> > This is a problem I have had for quite some time, across different > versions of software and OS. It seems to occur <20% of the time for me. > > I examined your "file65.mpg" and it appears to have no frequency content > above 16KHz, except for a handful of odd bursts at a few specific > frequencies > 16Khz during the first 5 seconds. The "tinny" sound would > appear to be due to frequency aliasing due caused by undersampling. > The aliasing would be the cause of the apparent "tinny" sound. > > What is the special significance to the 16Khz-cutoff, being that it's > exactly 1/3 of the sampling frequency? Well, if you're sampling a > signal at 32KHz, but that signal has frequency content above 16KHz, it > "folds back" around the 16KHz frequency. There seems to be just too > much higher-frequency content to be accounted for in this way in your > file. I'm puzzled by this. There seems to be more going on, involving > oversampling as well, perhaps, to arrive at this result. > > -Jeff
That's interesting. The card also supports a 32KHz sample rate, doesn't it? Is there a chance that something is using a 48KHz algorithm with a 32KHz sample rate? Noah _______________________________________________ ivtv-devel mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-devel
