Sound and video out of sync

[Antony Awaida <an...@apporto.com>]

Hi Guac team:

One of our users is using a music sequencer (Ableton LIve) and he
experiences a small lag between the sound and video. even though the
network latency between the desktop and the Guacamole/RDP server is pretty
good @35 ms.

What would cause such a delay.? I have read somewhere that the guac
protocol tries to make sure the sound and video are in sync on a frame.

Thanks!

-- 
Antony

ᐧ

Re: Sound and video out of sync

[Antony Awaida <an...@apporto.com>]

Hi Mike:

The delay according to the user is 250 ms....

Thanks,
Antony

ᐧ

On Tue, Jun 25, 2019 at 4:00 PM Mike Jumper <mj...@apache.org> wrote:

> On Tue, Jun 25, 2019 at 2:45 PM Antony Awaida <an...@apporto.com> wrote:
>
>> Hi Guac team:
>>
>> One of our users is using a music sequencer (Ableton LIve) and he
>> experiences a small lag between the sound and video. ...
>>
>
> How much lag does the user experience specifically?
>
> What would cause such a delay.? I have read somewhere that the guac
>> protocol tries to make sure the sound and video are in sync on a frame.
>>
>
> Guacamole does, yes. It's not an aspect of the protocol as much as it's an
> aspect of the client. The Guacamole server will stream both graphical and
> audio data as quickly as it can, essentially as soon as it's received.
> Along with this data is the "sync" timestamp that denotes the end of
> Guacamole's concept of a frame. The audio player within the client tracks
> the timestamp of the display (the timestamp of the graphics that most
> recently finished rendering) relative to the timestamp of the audio stream
> (the timestamp of the audio most recently played) and alters the scheduling
> of future audio playback to compensate for any time difference.
>
> In practice, whether the user will notice lag will also depend on the
> protocol used by the remote desktop server. If I remember correctly, RDP
> always sends audio packets that are roughly 300ms in size. Since that
> amount of audio will have to have accumulated remotely before the RDP
> server can send it, that guarantees at least that much lag before Guacamole
> even receives the packet.
>
> - Mike
>
>

-- 
Antony Awaida
CEO
www.apporto.com

Re: Sound and video out of sync

[Mike Jumper <mj...@apache.org>]

On Tue, Jun 25, 2019 at 2:45 PM Antony Awaida <an...@apporto.com> wrote:

> Hi Guac team:
>
> One of our users is using a music sequencer (Ableton LIve) and he
> experiences a small lag between the sound and video. ...
>

How much lag does the user experience specifically?

What would cause such a delay.? I have read somewhere that the guac
> protocol tries to make sure the sound and video are in sync on a frame.
>

Guacamole does, yes. It's not an aspect of the protocol as much as it's an
aspect of the client. The Guacamole server will stream both graphical and
audio data as quickly as it can, essentially as soon as it's received.
Along with this data is the "sync" timestamp that denotes the end of
Guacamole's concept of a frame. The audio player within the client tracks
the timestamp of the display (the timestamp of the graphics that most
recently finished rendering) relative to the timestamp of the audio stream
(the timestamp of the audio most recently played) and alters the scheduling
of future audio playback to compensate for any time difference.

In practice, whether the user will notice lag will also depend on the
protocol used by the remote desktop server. If I remember correctly, RDP
always sends audio packets that are roughly 300ms in size. Since that
amount of audio will have to have accumulated remotely before the RDP
server can send it, that guarantees at least that much lag before Guacamole
even receives the packet.

- Mike