[LAD] incorrect number of samples reading from /dev/dsp1

Johannes Kroll jkroll at lavabit.com
Tue Feb 1 15:05:49 UTC 2011


On Tue, 01 Feb 2011 07:49:15 +0000
Gordon JC Pearce <gordonjcp at gjcp.net> wrote:

> On Mon, 2011-01-31 at 21:55 -0800, farhan baluch wrote:
> > Hi All, 
> > 
> > 
> > I am trying to read data from a usb microphone and using the pretty
> > standard method of using ioctl's to setup the sampling rate, channels,
> > bits and block size . This all works so the device is correctly setup.
> > I then use "read" to read samples from the device which shows up
> > as /dev/dsp1. I get a lot more samples from this read command in one
> > second of recording than the set sample rate. E.g. if i set 10Khz on
> > one run i got 269312 samples. Looking at the raw data it looks like
> > there is a lot of duplication of data? is this common for the audio
> > input device? if so what kind of encoding is it (e.g with some
> > specific redundancy built in)? 
> > 
> > 
> > thanks
> > farhan
> 
> OSS has been obsolete for over a decade.  Don't use it.

OSS is alive and well, and actually better than ALSA in some respects.
It does software mixing well, and the API is reasonable. 

It's not supported on Linux out of the box though. If you are using
ALSA's OSS emulation layer, that one is obsolete, so you should prefer
the real ALSA API.





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