From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kai Vehmanen Date: Fri, 28 May 1999 20:25:41 +0000 Subject: Re: recording overrun Message-Id: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-sound@vger.kernel.org On Tue, 25 May 1999, georg.funke@netcologne.de wrote: > does anybody know what recording overrun is and why i get these > messages? A common problem when doing digital recording... Here's some info from OSS programming guide...: --cut-- A playback underrun situation occurs when the application fails to write more data before the device gets earlier data completely played. This kind of underrun occurs if: * The application needs too much time for processing the data. For example the program is being run on a too slow CPU or there are many other applications using the processor. Also loading audio data from a floppy disk is likely to fail. It is usually very difficult and often impossible to find a solution to this kind of underrun problem. Possibly only writing some parts of the program in assembler could help. * There is slight variations in amount of CPU time the application gets. In this way application which normally works fast enough may randomly run out of time. * The application attempts to work too much in real time. Having less data in the output buffer decreases delays in games and other real time applications. However the application must take care that it always writes new data before earlier written samples get completely played. Effect of underrun depends on the audio device. However in almost every case an audible defect is caused in the playback signal. This may be just a short pause, a click or a repeated section of signal. Repeated underruns may cause very strange effects. For example 100 underruns per second causes sometimes a signal having frequency of 100 Hz (it could be very difficult to find the reason which causes this effect). [...] A recording overrun situation occurs if the device fills the recording buffer completely. If this happens, the device is stopped and further samples being recorded will be discarded. Reasons of recording overruns are very similar than causes of playback underruns. A very common situation where playback overrun may occur is recording of high speed audio directly to disk. In Linux this doesn't work except with very fast disk (in other environments this should not be a problem). --cut-- -- Kai Vehmanen ----------------------------- CS, University of Turku, Finland : email mailto:kaiv@wakkanet.fi : projects, home page, etc http://www.wakkanet.fi/~kaiv/ : ambient-idm-rock-... mp3/ra http://www.wakkanet.fi/~kaiv/sculpscape.html