User`s manual

LOLA: Low Latency Audio Visual Streaming System
Before sending a connection request, it is recommended to check if the remote host is ready
for the connection. After inserting the remote host IP address, use the Check button provided in the
control panel below the IP address box: LOLA will issue a “ping request” the remote host at the
given IP address, and will also check if LOLA is running on it. An estimate of the network round
trip time (RTT) will also be provided. If the remote host is reachable, but LOLA is not running on it,
you should ask your remote party to start LOLA on his local host, and wait until your Check test
declares LOLA is also running remotely. The LOLA chat service (see section 4.10) works after you
enter the remote IP address and can help you in coordinating the connection with your remote
partner. Please note that if ICMP network protocol is filtered by network or local firewalls, the
“Check” test will fail.
If LOLA is running on the remote host, pressing the Connect button will cause the two
systems to negotiate the connection and start sending their audio/video streams to each other. Only
one node needs to initiate the connection. Note that while different video stream characteristics are
allowed for the two hosts (e.g., different frame rate, picture resolution, bit depth, color or b/w), the
audio stream parameters must be exactly the same. By default, 44100 Hz @ 16 bit, stereo, is
assumed. If during the negotiation an incompatible setup is detected, the two hosts will refuse to
connect. This is particularly important if audio multichannel is enabled.
4.3. Fine Audio/Video buffer tuning
Once the two hosts are connected, the user will have the opportunity to interactively change
the number of audio and video buffers used by the application, by using the Buffer Tuning panel
available in the Tools menu (Fig. 7a). The number of buffers can be set both using the control slider,
or by typing the value into the box below the slider. Adding buffers means also adding latency: this
fact indeed also let you fine tune the audio/video synchronization, for example by adding audio
buffers. A balance between optimal latency, quality and synchronization is something you should
try to achieve, depending on the specific configuration situation.
For the video, you can control both the number of buffers you use before sending your video
(“Local”) and the number of buffers you use before displaying the received remote video
(“Remote”). For the audio you can only control the number of buffers you use before rendering the
received remote audio.
The number of buffers can be increased if dropouts or glitches are noticed in the received
audio or video streams, due to network traffic or delay jitter, otherwise it should be kept as low as
possible to avoid additional latency. In a typical correct situation video buffers are both set to “0”,
and audio buffers should be possibly “0” and not exceed “5”. LOLA remembers the last settings of
all Audio and Video Buffers, and will also save them into all specific .ssn files you save; thus you
can also save the “ideal” settings you like for any remote location you connect to.