Hello Fabian,
> The bug fix is due for
> the next system update and is already out as a developer beta.
Could you tell me what is the version number of the beta developer version
Thanks.
> Message: 1
> Date: Thu, 13 Oct 2005 00:17:35 +0200
> From: Fabian Renn <email@hidden>
> Subject: Re: Usb Digest, Vol 2, Issue 226
> To: email@hidden
> Message-ID: <email@hidden>
> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
>
> Hello Gordon,
>
> the trick is not only to queue many frames, but also to queue more
> than one transaction. This way you assure a constant stream even if
> your kext doesn't get a lot of processor attention at one time. So
> your code will look like this:
>
> int cnt = 0;
>
> while ( cnt < numTransactions ) {
> while ( frameCnt < framesPerTransaction ) {
> frameList[cnt][frameCnt].frStatus = 0;
> .
> .
> .
> }
> cnt++;
> usbCompletion[cnt].target = this;
> .
> .
> .
> cnt = 0;
> while ( cnt < numTransactions ) {
> pipe->Read( ... );
> cnt++;
> }
> }
>
> In the completion routine you just restart the transaction.
>
> My best experience is two queue around 64-128 Frames per Transaction
> and queue about 8 Transactions ( lots of frames ). This way the
> system load will be at a minimum. If Latency is an issue for you than
> consider using the LowLatencyRead/Write commands. They will update
> the frame list right when a frame completes. This way a different
> thread ( in my case i used a high priority thread ( see the VLC
> source code for a good reference on how to create really cool high
> priority threads ) ) can read out the data according to the frame
> lists. Unfortunenateley, there is a bug in high speed isoc read
> transactions that won't update your read frame lists ( this bug only
> accurs for high speed read transactions ). The bug fix is due for
> the next system update and is already out as a developer beta. So you
> might want to grab that if you are doing high speed usb and latency
> is a issue.
>
> Greetings
>
> Fabian
>
>
> ------------------------------
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