Subject: Re: [linux-audio-dev] Total latency measurement tool
From: David Olofson (audiality_AT_swipnet.se)
Date: ke marras 10 1999 - 19:01:05 EST
On Wed, 10 Nov 1999, Paul Barton-Davis wrote:
> >I get 26 samples regardless of sample rate with the PCI128 and the
> >kernel driver. That is, all measurable latency seems to be in the
> >digital filters in the CODEC, and/or the driver + DMA.
> >
> >(I have a problem with ALSA and input, so I can't get reliable
> >results with it. Discovered that when running the audio input through
> >the "reverb" in my softsynth... The same full duplex code.)
>
> what does reliable mean ? for example, is this "stable" ?
>
> Delay: 61 samples
> Delay: 45 samples
> Delay: 49 samples
> Delay: 49 samples
> Delay: 73 samples
> Delay: 56 samples
> Delay: 72 samples
> Delay: 60 samples
> Delay: 72 samples
> Delay: 67 samples
> Delay: 76 samples
> Delay: 43 samples
> Delay: 69 samples
> Delay: 62 samples
> Delay: 80 samples
> Delay: 56 samples
> Delay: 57 samples
> Delay: 51 samples
> Delay: 48 samples
> Delay: 56 samples
> Delay: 63 samples
> Delay: 47 samples
> Delay: 56 samples
> Delay: 67 samples
> Delay: 43 samples
> Delay: 41 samples
> Delay: 56 samples
> Delay: 66 samples
> Delay: 57 samples
> Delay: 56 samples
No, it should be +/- 1 sample worst case. You can get more jitter if
the feedback level is too low or too high, but what we see here looks
exactly like what I get.
Remove the code that analyzes the input and generates the output
signal, run some signal through it (no feedback), and I think you'll
hear the reason for the jitter...
> if not, its a bug in ALSA 0.5.0 (OSS emulation?) that needs to be fixed.
Don't know if it's my bug or in ALSA. The code works with the kernel
es1370 driver, and other full duplex code that works with ALSA's OSS
emulation.
//David
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