ASC (application stream control)

A measure used to predict when the audio or video will pass through an output jack.

capabilities tree

The hierarchy of all ML devices in the system. The capabilities tree contains information about each ML device. An application may search a capabilities tree to find suitable media devices for operations you wish to perform.


An audio, image or video compressor/decompressor.


The graphical display used for the user interface on a computer; compare to video.

in-band messages

When an application waits for all previously enqueued messages to be processed before influencing a device. See also out-of-band message.

interlaced video

Video that is divided into two fields (upper and lower). Video standards that use interlacing are NTSC, PAL, and SECAM. In interlaced video, the first field is transmitted first (odd lines) then the second field of the frame is transmitted (even lines).


The method of laying out the lines of interlaced video data in memory. In interleaved mode, the lines of the frame are stored as follows in one buffer:


In noninterleave mode, the lines of the fields as stored as follows:

  • In one buffer:

    f1-line1,f2-line2,f1-line3 ... f1-lineN

  • In another buffer:

    f2-line1,f2-line2,f2-line3 ... f2-lineN


A logical device that is an interface in/out of the system. Examples of jacks are composite video connectors and microphones. Jacks often, but not necessarily, correspond to a physical connector -- it is possible for a single ML jack to refer to several such connectors. It is also possible for a single physical connector to appear as several logical jacks.

MSC (media stream count)

A measure of the number of media samples that have passed though a jack. This is useful to synchronize media streams.

logical device

A jack, path, or transcoder. See also physical device.

out-of-band message

When an application wishes to influence a device without first waiting for all previously enqueued messages to be processed. See also in-band message.


A logical device that provides logical connections between memory and jacks. For example, a video output path transports data from buffers to a video output jack. Paths are logical entities. Depending on the device, it is possible for more than one instance of a path to be open and in use at the same time.


The connections from memory to the transcoder, and from the transcoder to memory.

physical device

A device that corresponds to device-dependent modules in ML. Typically, each device-dependent module supports a set of software transcoders or a single piece of hardware. Examples of devices are audio cards on a PCI bus, DV camcorders on the 1394 bus, or software DV modules. Each device-dependent module may expose a number of logical devices.


The highest level in the capability tree hierarchy. The system is the machine on which your application is running. This machine is given the name ML_SYSTEM_LOCALHOST. Each system contains one or more devices.


A logical device that takes data from buffers via one or more input pipes, performs an operation on the data, and returns the data to another buffer via an output pipe. Example transcoders are DV compression and JPEG decompression.

UST (unadjusted system time)

A special system clock that runs continuously without adjustment. This clock is used to synchronize media streams.


The type of signal sent to a video cassette recorder or received from a camcorder; compare to graphics.