Date: Tue, 26 Aug 1997 21:28:57 +0200 (SAT) From: Ian Freislich <iang@digs.iafrica.com> To: dec@phoenix.its.rpi.edu (David E. Cross) Cc: multimedia@freebsd.org Subject: Re: Stuttering in Mpeg3 playback Message-ID: <E0x3RIP-00014d-00@brane.digs.iafrica.com> In-Reply-To: <Pine.BSF.3.96.970826131922.8899A-100000@phoenix.its.rpi.edu> from "David E. Cross" at "Aug 26, 97 01:24:45 pm"
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David Cross wrote: > I have noticed a distinct 'stutter' in soundplayback on mpg123 using > OSS/FreeBSD 3.8h with an Ensonq Soundscape Elite. The problem is that > if the machine is running even with a moderate load the sound playback > suffers small skips (even if the processor still has as much as 25% > idle time). The problem is also noticible in X if I just switch focus > by moving the mouse. (moving the mouse without changing focus does > not cause the skip). It seems like the card is not being saturated > with data. This is odd, because with a 64K DMA buffer (I believe the > default with OSS), it should be a full 1/3 second of buffered data. I've noticed a similar problem on my system, although mine has the stutter for about the first 5 seconds of playback during which time, I guess, the DMA buffer is being filled. Once this period has passed the playback is pretty good except for small breaks or stutters every 40 or so seconds. It seems this happens whether my system is loaded or not. FWIW: I have the old Gravis Ultra Sound 3.4 with 1024k RAM on board and I'm running the guspnp17 driver. > Has anyone else experienced this. Is it a problem with my sound card, > the kernel, or OSS? I have found that this problem is less pronounced if I use mpg123 version 0.59g. I suspect a kernel/OSS problem since I made some mods to the buffer routine in mpg123 to only start playing once it had filled up the buffer. In this test I set the buffer size to 4096k. Even when it started playing with 4096k of pre-buffered audio it still stuttered. Something else of note is that when it started playing I used to get those 'isa_dmastart: channel %d busy' messages for the duration of the stutter until that routine was moved into the sound driver or the message was removed from isa.c. -- igf (Ian Freislich)
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