Re: Latency Issue
Re: Latency Issue
- Subject: Re: Latency Issue
- From: Dirk Musfeldt <email@hidden>
- Date: Fri, 30 Jan 2004 09:27:18 +0100
Hi Eric,
regarding the QT Sequencer Grabber:
The QTSG has a large latency you can't avoid. This seems to be due to using
the old SoundManager that simply waits for some buffers to fill up (0.5s?)
before it starts playing.
Avoid the SG if you want little latency, at least as long as the SG uses the
old SoundManager. (version 3.0 still deriving from OS 8?)
>
Hi all,
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>
I have a question about the latency issue. Here is the situation:
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I am developing an audio input driver for a PCI device. Due to the hardware
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limitation, the dma transfer to the audio stream buffer 4K at a time and the
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currentSampleFrame will be updated accordingly. I have the ring buffer 16K
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large so there would be 4 DMA before reaching end of the ring buffer. When the
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last DMA chunk finished by a hardware interrupt callback, the takeTimeStamp()
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will be called.
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When i do a software playthru test to play back the captured audio data, i
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found that there are significant latency happened to the audio signal when i
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compare with the hardware playthru output from my input device. I have looked
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into one of the archives
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http://lists.apple.com/archives/coreaudio-api/2003/Jun/17/fismixable.017.txt
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memtioned here, but seems like it didn't solve the problem. changing the
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setSampleLatency() value didn't seems to help. So what's wrong with my setup
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and which area i should look into to fix it?
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I also found that if i do software playthru using Sequence Grabber from QT, it
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would have a much larger latency when playback. Is there something i missed in
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the setup? How can i correct this problem?
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Thanks for your help
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>
Eric
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1
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With kind regards
Dirk Musfeldt
Meilenstein Mac OS Software
Neue Strasse 5
D-31582 Nienburg
Germany
Tel: +49 (0) 5021 91 24 44
Fax: +49 (0) 5021 91 24 45
<
http://www.meilenstein.de/>
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