Veejay Advanced

November 17, 2008

###Plugins

Veejay can load both LiViDo and Frei0r plugins.On 32-bit systems, there is also support for FreeFrame. By default,veejay looks in a few common locations to find your plugins. Also, you can configure additions paths to look for plugins:

$ mkdir ~/.veejay
$ vi ~/.veejay/plugins

The contents of the file can look like:

/usr/local/lib/freeframe
/usr/local/lib/frei0r-1

Veejay will pick up the plugins the next time you start it.

##VIMS

VIMS is veejay's internal message system - its simple and in plain ASCII.
All control data is distributed via VIMS. Each (atomical) message consists of an Action Identifier and a list of zero or more Arguments which can be used to control Video Clips, Video Streams, the Effect Chain and many other things.
Reloaded, veejay's client, uses a dual socket to read status and write back VIMS
messages.

VIMS allows events to be triggered through:
SDL Keyboard Event (libsdl)
OSC (Open Sound Control)
And Itself

After intalling veejay, you will have a commandline utility 'sayVIMS' which you
can use to send text messages.

Use the command
$ veejay -u -n |less
to dump all VIMS messages.

###The Message Format

A message is described as:

: ;

Examples:

080:;  
099:0 0;  

The action identifier is a 3 digit number describing a Network Event
The colon is used to indicate the start of the Argument List and must be given.

The Argument List is described by a printf() style formatted template
which describes the number and type of arguments to be used.

The semicolon must be given to indicate the end of this message

###Reserved Values
Some reserved numbers:

###Images

Using images as a source

Veejay currently supports jpeg, png and bmp images as a source, meaning you can mix static images with moving video.

Writing images

Making screenshots (scales and save image to file)

330:

;

for example

$ sayVIMS "330:640 480 screenshot.png;"

###Sound output

Veejay plays audio through Jack

You must start the jack server prior to starting Veejay:

$ jackd
$ veejay video-file.avi

If the audio samplerate differs (Jack plays 48Khz, veejay plays 44.1Khz), you need to setup jack in the proper samplerate.

$ jackd -r 44100

###Performance tuning

Veejay's performance depends much on the memory bandwidth, CPU and disk access times.

For HDTV (1280x720) mjpeg, you need at least a 2.5 ghz and 1 GB of RAM. The faster your CPU, the better since decoding is cpu intensive - like some of veejay's FX.

For full PAL/NTSC resolutions (720x576 resp. 720x480) DV/Mjpeg you need at least a 1.5 ghz, for lower resolution (352x288) you can do fine with a 500-800 mhz PC.

If you need to record without framedrop, you can do so by disabling audio and disabling synchronization with the commandline options -a0 -c0

On modern CPU's (i686) your best bet is working in RAW or MLZO (compressed) YUV 4:2:0 / 4:2:2 if you need the little extra for FX rendering.

Typical for laptops is slow diskspeed access, on my 1.8 ghz dell latitude laptop the best I get is an average of about 20.0 mb/sec which is barely sufficient for playing full PAL avi's containing RAW YUV.

(you can test yours with hdparm -T -t /dev/hdX)

###Caching

Veejay has a caching mechanism that loads (compressed) images from disk into RAM. Frames furthest away from the currently played position will be discarded first when the cache size limit is reached. By default, this limit is set to 30% of your system's memory.

There are two commandline options you can use to change the behaviour of the cache:

-m / --memory [percentage of available RAM to use]

-j / --max_chain [maximum number of simultaneous samples to cache]

If you mix a lot of (short) different samples over eachother, you might want to set "-j5 -m50" . If you would have 100 MB RAM, veejay will consume up to 50%, dividing the memory available for 5 different samples, thus max. 10 MB RAM per sample.