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Re: [Qemu-devel] USB streaming [Re: [PATCH 18/18] usb: add ehci adapter]
From: |
David Ahern |
Subject: |
Re: [Qemu-devel] USB streaming [Re: [PATCH 18/18] usb: add ehci adapter] |
Date: |
Tue, 17 May 2011 13:18:15 -0600 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110421 Fedora/3.1.9-2.fc14 Thunderbird/3.1.9 |
On 05/17/11 13:10, David Ahern wrote:
>> Note that once every while a packet will get lost since normally a usb
>> device is synced to the usb frame timer, but the real and emulated frame
>> timer
>> are not synced, so eventually a packet will get lost.
>
> I noticed that as well. The guest uhci driver (linux at least) guesses
> where to put the initial request (10 frames out as I recall). From there
> the requests need to flow - responses come into the guest, requests are
> appended to the stream.
>
> One missed packet in the guest causes the driver to "start over" -- ie,
> it's no longer a stream, but an initial request placed 10 frames out.
> That causes an ugly jitter, and if the qemu controller happens to be
> past the '10 frames out' guess by the OS you get a 1+ sec gap of silence.
Oh yea, as I mentioned in the URL modifying the guest driver to have
more outstanding URBs (at least 4 URBs with 5 packets per URB) was a key
aspect of the solution as well -- keeping the guest OS and controller
from losing sync.
David
>
> David
>
>>
>> Regards,
>>
>> Hans
>
>
- Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter, (continued)
- Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter, David Ahern, 2011/05/17
- Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter, Gerd Hoffmann, 2011/05/17
- Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter, David Ahern, 2011/05/17
- Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter, Hans de Goede, 2011/05/17
- [Qemu-devel] USB streaming [Re: [PATCH 18/18] usb: add ehci adapter], David Ahern, 2011/05/17
- Re: [Qemu-devel] USB streaming [Re: [PATCH 18/18] usb: add ehci adapter], Hans de Goede, 2011/05/17
- Re: [Qemu-devel] USB streaming [Re: [PATCH 18/18] usb: add ehci adapter], David Ahern, 2011/05/17
- Re: [Qemu-devel] USB streaming [Re: [PATCH 18/18] usb: add ehci adapter],
David Ahern <=
- Re: [Qemu-devel] USB streaming [Re: [PATCH 18/18] usb: add ehci adapter], Hans de Goede, 2011/05/18
- Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter, Hans de Goede, 2011/05/17
- Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter, David Ahern, 2011/05/17
- Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter, Blue Swirl, 2011/05/17
- Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter, David Ahern, 2011/05/17
- Re: [Qemu-devel] [PATCH 18/18] usb: add ehci adapter, Andreas Färber, 2011/05/21
Re: [Qemu-devel] [PATCH 00/18] usb patch queue: add usb 2.0, Anthony Liguori, 2011/05/16