Re: Audio Hardware Plugin and Drift
Re: Audio Hardware Plugin and Drift
- Subject: Re: Audio Hardware Plugin and Drift
- From: Dirk Musfeldt <email@hidden>
- Date: Mon, 29 Aug 2005 16:24:29 +0200
Hi Jeff,
> The most likely culprit is the time stamps you provide to the IOProcs
I provide mSampleTime. I have also tried with hostTime taken when the
process callback starts running for both inNow and inInputTime parameters.
> and how you are handling the time translation functions.
Neither DeviceGetCurrentTime() nor DeviceTranslateTime() function are ever
called. When should these be called?
Our plug-in is called with a CFMessagePort message from a daemon when audio
is to be processed. The plug-in in turn processes the registered
AudioDeviceIOProcs.
The audio belongs to an AV stream and I have noticed the drift just by
watching both audio and video.
When I dropped the plug-in in favor of a simple output from the daemon
(similar to the PlayAudioFileLite sample) I did not notice any drift.
What is essential for the timestamps?
> Of course,
> it's hard to give any advice with so little info about the problem.
> Could you elaborate a bit on both how your plugin works as well as on
> how you are doing the testing and I'll try to help you figure out
> what you're doing wrong.
>
> On Aug 26, 2005, at 6:17 AM, Dirk Musfeldt wrote:
>
>> Hi,
>>
>> I have an audio hardware plugin that provides a system-wide audio
>> input from
>> user space.
>>
>> It seems to be running fine. But unfortunately I have found out
>> that there's
>> some drift in the audio chain, i.e. the audio is not played from the
>> speakers as fast as it is processed by the AudioDeviceIOProcs.
>>
>> On some machines the drift is noticeable after one hour on other
>> machines
>> after four hours or more.
>>
>> Does anyboy have an idea what might be the cause and how I could
>> prevent
>> that?
>>
>>
>> Regards
>>
>> Dirk
Regards
Dirk
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