Well as a mather of fact I'm just trying to disable all these features that
increase quality. I want to show my students that enabling, for example,
reliable UDP increases the perceived quality. Or that disabling buffering
will result in jerky playback due to packets arriving after presentation
time.
I also want them to understand the relationship between a video sequence and
the bursty traffic that is generated by streaming this file (every frame
period a burst of a frame is sent)..
So are my questions feasible?
regards, Philippe.
----- Original Message -----
From: "George Cook" <email@hidden>
To: "Philippe De Neve" <email@hidden>
Cc: "Darwin List" <email@hidden>
Sent: Wednesday, January 05, 2005 3:52 PM
Subject: Re: Instant-On & double frame rate
Philippe:
It sounds like you are trying to minimize latency. There have been
discussions on this on the streaming server list around this topic.
Realize however that streaming is not video conferencing (where low
latency is a design point). With streaming, latency increases quality
of service by buffering, packet retransmission, etc. These are
important design points for streaming, and the reason that there is
more latency in streaming than video conferencing.
Here are some quotes from the mailing list archives that might be
helpful to you:
> Let me start by mentioning that the following s being provided for
> testing purposes and with the caveat that making the change below is a
> completely unsupported configuration. However, you might giving it a
> try.
>
> Regarding reducing latency when viewing a reflected stream (.sdp)
> through a QuickTime/Darwin Streaming Server, you might try changing
> the "reflector_buffer_size_sec" property in the streamingserver.xml
> file. For example, reduce the reflector's buffer delay from 10
> seconds to 0 seconds (pref="reflector_buffer_size_sec").
>
> Then, as root or the admin user edit the
> /Library/QuickTimeStreaming/Config/streamingserver.xml file, and
> search for this property:
>
> <PREF NAME="reflector_buffer_size_sec" TYPE="UInt32" 10</PREF>
>
> Change it to:
>
> <PREF NAME="reflector_buffer_size_sec" TYPE="UInt32" 0</PREF>
>
> Write the xml file back to disk (make sure that when you save it, save
> it as plain text with .xml extension, don't save it accidentally as
> ..rtf, etc.)
>
> Now, send a SIGHUP to the QTSS child process (the higher PID number)
> or else stop/restart the QuickTimeStreamingServer using the Streaming
> Web Admin interface.
>
> To change things back, just re-edit the xml file and make the value be
> 10 again, and then restart the streaming server...
> As for your original question, to turn disable overbuffering, you can
> change the
> following items in the
> /Library/QuickTimeStreaming/Config/streamingserver.xml file
>
> <!-- Rate at which to overbuffer: number of times the data rate -->
> <PREF NAME="overbuffer_rate" TYPE="Float32">2.0</PREF>
>
> Change this pref value to 1.0:
> <PREF NAME="overbuffer_rate" TYPE="Float32">1.0</PREF>
>
> This will cause the server to send at the rate it is encoded, and not
> faster. There will be an initial overbuffering of data for the first
> one second. To turn off all overbuffering, also modify the following
> pref:
>
> <!-- This is also the minimum time the server will wait
> between sending packet data to a client -->
> <PREF NAME="send_interval" TYPE="UInt32">50</PREF>
>
> Change this pref value to 0:
> <PREF NAME="send_interval" TYPE="UInt32">0</PREF>
>
> <PREF NAME="disable_overbuffering" TYPE="Bool16" false</PREF>
>
> Change this pref value to true:
> <PREF NAME="disable_overbuffering" TYPE="Bool16" true</PREF>
>
> This will turn off overbuffering completely.
On Jan 5, 2005, at 9:25 AM, Philippe De Neve wrote:
> Hi folks,
>
> I've got two questions:
> 1)
> I've noticed that the DSS sends 2 frames simultaneously and waits then
> for 2
> frame periods (in my case about 66 ms for a 30 fps sequence). Can I
> disable
> this so every 33 ms a frame is send?
>
>
> 2)
> With the Instant-on feature of quicktime it is possible to change the
> buffering time I presume. But changing the Instant-On slider in the
> Quicktime Preferences does not result in a change in the buffering
> time. It
> stays the same (3s). How can I set the buffering time (to zero)?
>
> tnx for all help, Philippe.
>
>
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--
Nothing in the world can take place of persistence.
Talent will not; nothing is more common than unsuccessful men with
talent.
Genius will not; unrewarded genius is almost a proverb.
Education will not; the world is full of educated derelicts.
Persistence and determination alone are omnipotent.
~ Calvin Coolidge
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