Table 3-1 summarizes the configuration files that the SGI Media Server uses to configure hardware and other SGI Media Server resources. These files assign controls to hardware ports that affect device and system operation.

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Note: You can also use MVCP SET commands to alter control values but the changes will only persist until the next VST restart. In contrast, control values set in the configuration files persist from a VST start until changed by a SET command.

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For a detailed discussion of the SGI Media Server controls and values applicable to each configuration file and device, see the vst-control(5) man page. The file formats and organization for the following files are described in the following sections of this chapter:

Table 3-2 describes the various peer directories of /usr/vtr/config.

A device file contains variables called controls that map device register settings or establish settings for SGI Media Server interaction with peripheral control systems, such as the Harris Automation ADC100. The controls consist of name-value pairs. The device register settings establish specific behaviors, such as the compression format for video ingestion. Exactly one device file exists for each active media processing device in the SGI Media Server infrastructure.

vtr.media.video.input.compression.type mpeg2

vtr.media.mpeg.bit_rate 50000000

vtr.media.video.input.vitc.line_offset 14

vtr.media.clip.start.mode vitc

vtr.media.audio.input.channels 1

vtr.media.audio.input.channel_map.source “A”

vtr.media.audio.input.channel_map.channel_pair “1”

You use VST controls in files in the /usr/vtr/config/ system-defaults directory to specify default, systemwide behavior. For example, the file main might contain the following:

vtr.main.timing_standard 625

This line sets the default timing mode for the SGI Media Server to 625. This implies that the SGI Media Server will only process PAL-based video signals.

If a Little Red linear timecode (LTC) processor periperhal is attached, the file /usr/vtr/config/system-defaults/time might contain a global offset for Little-Red LTC processing:

vtr.time.offset -27000000

See the vst-controls(5) man page for detailed information about all system controls.

The PCI-VIDAUD-MSB-B multiformat codec ( MFCODEC) devices support several file formats for video compression: DIF, SGI MPEG-2, SMPTE 360M (playout only), and MXF. The DIF video format supports DVCPRO 25, DVCPRO 50, DVCAM, and DV (16-bit/48 Khz audio only) fixed-sized compression. To enable MPEG-2 video compression, add the following line to the appropriate MFCODEC_n file:

vtr.media.video.input.compression.type mpeg2

Alternatively, you can use the SET command from mvcp to specify the format directly in the unit context. Similarly, to enable DVCPRO 50 video compression, add the following line to the appropriate MFCODEC_n file:

vtr.media.video.input.compression.type dvcpro50

IMX ingest requires an IMX-enabled PCI-VIDAUD-MSB-B card. The standard VST controls (see the vst-controls(5) man page) configure these cards for processing DVCPRO 25, DVCPRO 50, DVCAM, DV (16-bit/48 Khz audio only), or SGI MPEG-2 video signals for playout and ingest.

To create an IMX-compatible clip, the following controls must be set within the unit context with the MVCP SET command or using entries in a device configuration file:

vtr.media.mpeg.bit_rate 50000000
vtr.media.video.input.constant_bit_rate true
vtr.media.input.compression.type mpeg2
vtr.media.video.input.compression.gop_structure I
vtr.media.video.input.compression.gop_size 1

For strict compliance with SMPTE 356M-2001, the 50 Mbps value must be used for vtr.media.mpeg.bit_rate. However, an IMX-compatible deck can play clips recorded at other constant bit rates.

MPEG-2 video coding can assume many compression formats, depending on the group of pictures ( GOP) structure and GOP size multiplier. The PCI-VIDAUD-MSB-B MFCODEC supports four unique GOP structures: I (the default), IP, IPB, and IPBB—the standard MPEG names. For a detailed discussion of MPEG video coding, consult the website http://www.mpeg.org.

Each GOP structure has a GOP period, which is the interval between two successive occurrences of the GOP structure, exclusive of the I-frame. Table 3-3 defines the GOP period for each supported GOP structure.

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Caution: Attempts to apply unsupported GOP structures may generate unpredictable results.

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Each GOP structure provides variable compression encoding, though longer GOP structures typically produce higher video frame compression, thereby reducing video storage consumption during ingestion. Longer GOP structures have a drawback: they potentially introduce information loss through the encoding compression operation. The vtr.media.mpeg.bit_rate control, when set to a very low compression rate (less than 10000000), may contribute to information loss during encoding, though information loss depends on scene content changes and several other factors. Information loss arising from too much compression may occur during playout in the form of poor image reproduction or unwanted image artifacts.

For each supported GOP structure, the default GOP size is 1. There are many combinations of GOP size and GOP structure. These combinations are restricted by the following rule: the GOP period must evenly divide the GOP size.

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Caution: Failure to obey this rule may lead to unpredictable results.

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For example, Table 3-4 defines examples of valid GOP sizes, their periods, and structures.

To enable MPEG-2 video compression with the default I-frame compression and GOP size 1, add the following line to the appropriate MFCODEC_n file:

vtr.media.video.input.compression.type mpeg2

Alternatively, you can use the SET command from mvcp to apply it directly in the unit context. To further compress and encode a video stream, add the following lines:

vtr.media.video.input.compression.type mpeg2

vtr.media.video.input.compression.gop_structure IPBB

vtr.media.video.input.compression.gop_size 6

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Caution: Selecting unreasonable values for vtr.media.video.input.compression.gop_size may lead to unpredictable results. A maximum gop_size of 15 is considered an extreme upper bound for the MFCODEC.

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The MFCODEC further supports two distinct forms of compression sampling: 4:2:0 and 4:2:2. The control vtr.media.video.input.compression.sampling has a default value of 422, which selects 4:2:2 compression sampling. To enable 4:2:0 compression sampling, add the following line to the appropriate MFCODEC_n file:

vtr.media.video.input.compression.sampling 420

Alternatively, you can use the SET command from mvcp to apply it directly in the unit context.

The following controls affect only MPEG-2 compression.

They are ignored for DVCPRO 25, DVCPRO 50, DVCAM, and DV (16-bit/48 Khz audio only) video ingestion.

For the MFCODEC devices, you can select the audio port map and source map for both input and output.

vtr.media.audio.input.channel_map.source value_0value_1value_2value_3

vtr.media.audio.input.channel_map.source EEEA

Channel Map/Channel Pairs Control

The vtr.media.audio.input.channel_map.channel_pair control selects which audio input of a particular type goes to each MFCODEC input pair. The choices are 1, 2, 3, or 4 for embedded; 1, 2, or 3 for AES/EBU; or 1 for analog. This control, combined with the vtr.media.audio.input.channel_map.source control, selects what audio goes to each of the four MFCODEC input pairs . This can be changed on a clip-by-clip basis.

The syntax for the vtr.media.audio.input.channel_map.channel_pair control is as follows:

vtr.media.audio.input.channel_map.channel_pair src_0src_1src_2src_3

Each src_i variable represents the source choice for MFCODEC input pair i. The possible values are 1 (source 1), 2 (source 2), 3 (source 3), and 4 (source 4). The following is an example:

vtr.media.audio.input.channel_map.channel_pair 2314

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Note: For each MFCODEC input pair, its source choice (src_i) has a possible value of 1, 2, 3, or 4. However, as noted previously, these four source choices are not always available for each input type. For instance, if analog was selected for a particular MFCODEC input pair on the vtr.media.audio.input.channel_map.source control, the only valid value for the source is 1.

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vtr.media.audio.input.channel_map.source EEEA
vtr.media.audio.input.channel_map.channel_pair 1231

vtr.media.audio.input.channel_map.source EEEA
vtr.media.audio.input.channel_map.channel_pair 1131

vtr.media.audio.input.channel_map.source DDEA
vtr.media.audio.input.channel_map.channel_pair 2311

Merlin Port 1 - PCI-VIDAUD-MSB Video (module=001c01 xtalk=14 slot=1)
Merlin Port 2 - PCI-VIDAUD-MSB Video (module=001c01 xtalk=14 slot=2)
Merlin Port 3 - PCI-VIDAUD-MSB Video (module=001p02 xtalk=12 slot=1)
Merlin Port 4 - PCI-VIDAUD-MSB Video (module=001p02 xtalk=12 slot=2)
Merlin Port 5 - PCI-VIDAUD-MSB Video (module=001p02 xtalk=15 slot=1)
Merlin Port 6 - PCI-VIDAUD-MSB Video (module=001p02 xtalk=15 slot=2)

vtr.media.audio.input.channels 2

vtr.media.audio.input.channel_map.source “AE”

vtr.media.audio.input.channel_map.channel_pair “12”

UADD MFCODEC_3 * EXCL *
U2
200 OK
SET U2 MED vtr.media.audio.input.channel_map.channel_pair ““
200 OK
SET U2 MED vtr.media.audio.input.channel_map.source ““
200 OK
SET U2 MED vtr.media.audio.input.channels 0
200 OK

To configure the SGI Media Server so that it can be controlled by remote devices, use the /usr/vtr/config/control-in.conf file . The SGI Media Server supports devices that use one of the following protocols:

The /usr/vtr/config/control-in.conf file has three parts:

The control port and signal configuration lines are described in the following subsections.

Control Port Configuration Line

You use the configuration file /usr/vtr/config/control-in.conf to specify basic connection parameters between the controlling devices (Sony and VDCP) and the SGI Media Server. Connection parameters include such information as which serial port controls a specific video board and the precise means of control interaction between the port and video board.

For each serial port to be connected to a controlling device (such as an automation or edit controller), insert a line in the /usr/vtr/config/control-in.conf file that uses the following format:

protocol type port speed parity signalport rate latency [clips=path/*]

The following line shows a sample configuration:

sony rs422 4 38400 1 1  29.97 0 clips=press-conference/*

This example specifies that a controlling device using the Sony-compatible VTR protocol is connected via an RS-422 serial line to serial port 4 on the server. The serial connection speed is 38400 bits/s, using odd parity. The device is controlling the video port identified by the “signal 1” configuration line (also specified in control-in.conf) and is using a zero-frame command latency so that commands are executed as quickly as possible. The preroll should always be 0, except for VDCP controllers, for which the preroll is 3. The ingested content to be stored in the directory /usr/vtr/clips/press-conference.

The following sections describe each variable in this configuration line.

protocol

Use the value that corresponds to the protocol used by the device you are configuring to work with the SGI Media Server. The valid values of protocol include the following:

sony, p2		Sony-compatible VTR RS-422 control protocol
louth		VDCP
mvcp		SGI MVCP
hsip		Horita Serial Interface Protocol
little-red		Miranda Little-Red linear timecode reader protocol

type

The valid values of type include the following:

rs232		RS-232 control connection
rs422		RS-422 control connection
tcp		Socket-based TCP/IP connection

These values must correspond to the type of connection between the control video device and the SGI Media Server. The type of cable you use to connect the video device and the server determines this value.

port

The value of port specifies the serial port number for RS-232 and RS-422 connections. For example, to specify that the device is connected to port 2 (sometimes referred to as ttyd2), specify just the numeral 2. For TCP connections, port specifies the TCP port number.

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Note: Serial and TCP ports (communications ports) are unrelated to video ports (signal ports).

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speed

The speed value specifies the connection speed of the serial connection between the server and the controlling device, usually 38400. On rare occasions, 9600 is used. For TCP connections, enter a hyphen (-) for this setting.

parity

The optional parity setting can have one of the following values:

0		No parity
1		Odd parity
2		Even parity

Parity is usually odd (1). On rare occasions, even or no parity is used.

signalport

The signalport value specifies the signal (video) port that is controlled by this remote device connection. This value is identified by a signal configuration line in the file control-in.conf. A prefix character of ”–“ implies the port is an ingest port. By default, a port is a playout port unless the port number is prefixed by “–“. For more information, see “Signal Configuration Line”.

rate

The rate value specifies the frame-rate and drop-frame mode for timecodes exchanged over the control connection. The following are the valid values:

25		625/50 video
29.97		525/59.94 video (drop-frame)
30		525/59.94 video (not drop-frame)

latency

When the SGI Media Server receives a command, the command can apply only to the next frame to enter the video port output queue. For example, if the video port output queue holds three frames, the first frame that can be affected by an incoming command is the third frame in the queue. If a stop command is received, the first two frames in the video port output queue are displayed; the third is not displayed because it is affected by the stop command.

You can modify the number of frames that display before a command begins by setting the latency value. Valid values are 0 or positive integers. A value of 0 starts the command's effect as soon as possible, but the command latency is always greater than 0. The minimum command latency is the sum of two values, as shown in the following:

minimum_command_latency = fixed_latency_value + 1

A small number for latency increases the risk that a frame may be missed (repeated) because of system load. A large number increases the latency in responding to transport commands such as play, stop, or pause.

Some commands in the Sony protocol imply a predefined frame delay; latency does not affect these commands.

For the MVCP TCP port, make sure that the control-in.conf file includes a control port configuration line:

mvcp tcp 5250

5250 is the standard MVCP control port number. The initial control-in.conf file installed with the VST software includes this line.

clips=path/*

This optional field specifies the directory under /usr/vtr/clips to contain the ingested content.

signal 1 MFCODEC_4

# Control input configuration
#
# Control ports
#
#   Each control port is configured with a line of this form:
#
# <prot> <comm type> <comm port> <speed> <parity> <video> <rate>
#        <preroll> <var>
#
#     prot:         Protocol (louth, odetics, sony, mvcp)
#     comm type:    rs232, rs422 (on Origin only), tcp
#     comm port:    Serial port number (e.g., 1, 2), or TCP port number
#     speed:        Bits/sec (default=38400) (use - for TCP)
#     parity:       0=none, 1=odd, 2=even (default=odd) (use - for TCP)
#     signal port:  default signal port number (use -port for louth
#                   input port)
#     frame rate:   frames/sec (29.97, 25)
#     preroll:      command preroll (# frames)
#     var:          variable arguments, currently support name=string

# This defines the normal MVCP TCP control port

mvcp tcp 5250

# Other control ports
 
louth   rs232 1 38400 1 2 29.97 3
louth   rs232 2 38400 1 -2 29.97 3

sony    rs422 3 38400 1 1 29.97 3

louth   rs422 5 38400 1 3 29.97 3
louth   rs422 6 38400 1 -3 29.97 3

hsip    rs232 4 9600  0 1 29.97
#
# Signal ports
#
#   Each signal (video) port is mapped from a port number to port name
#   with a line of this form:
#
#   signal <port number> <port name>
#
#     port number:      Disk port number (> 0)
#     port name:        Video server port name (e.g., MFCODEC_3)

signal 1 MFCODEC_4
signal 2 MFCODEC_3
signal 3 MFCODEC_2
signal 4 MFCODEC_1

To configure the SGI Media Server server so that it can control other VTR-like devices, use the /usr/vtr/config/control-out.conf file.

Use this file also to specify basic connection parameters between the SGI Media Server and the VTRs to be controlled. Connection parameters include such information as which serial port controls which VTR and how. For each VTR controlled by the SGI Media Server using the Sony protocol, add a line in the /usr/vtr/config/control-out.conf file that uses the following format:

protocol    connection    serial_port     speed    parity

The following line shows a sample configuration:

sony    rs422    4    38400    1

The line has the same meaning when p2 is substituted for sony.

The following sections describe each variable in this configuration line.

The /usr/vtr/config/vtrd.conf file specifies information that controls the VTR daemon process ( vtrd). The daemon process is the parent for all instances of the vvtr child process, the process executing for video operations. For more information about the vtrd.conf file format, see the vtrd(1) man page.

You can use the /usr/vtr/ports.conf file to create logical names for the physical video ports on the SGI Media Server. For each port, include a line in the configuration file with the following syntax:

port physicalname logicalname description 

For example:

port MFCODEC_0 POTUS "WHITEHOUSE OVAL OFFICE, POTUS"
port MFCODEC_1 MAINEB "1ST AND MAIN, Eastbound"
port MFCODEC_5 RJM "RIJKSMUSEUM"
port MFCODEC_6 MPEG2 “MPEG RECORDING, CAMERA 1”
port MFCODEC_7 DVC50 “DVCPRO50 RECORDING, CAMERA 2”

The description field must be enclosed by quotation marks if it contains spaces. The physical port name MFCODEC_n references the underlying hardware. One physical port name is assigned to each installed PCI-VIDAUD-MSB codec. The physical port name is fixed at the factory. The logical port name POTUS may be used for unit creation and other unit-specific operations, such as changing control values using the mcpanel or mcstat command.

You can configure the SGI Media Server to supports either 525/59.94 or 625/50 operation. A few operating characteristics default to 525/59.94, including the MVCP timing mode. Refer to the MVCP FRAT command documentation in the mvcp(5) man page.

To change the default timing, include the following control setting in the system defaults file /usr/vtr/config/system-defaults/main:

vtr.main.timing_standard 625 

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Note: The system timing standard controls the default video output timing only if the control  vtr.media.video.output.timing is not changed from its default value of system. The vtr.media.video.output.timing control appears in the /usr/vtr/config/system-defaults/MFCODEC_n files.

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The maximum direct memory access (DMA) size limits the maximum amount of data that can be transferred to or from the filesystem in a single operation. The default maximum DMA size is 4 MB, which is too small for most installations. To increase the system's maximum DMA size, use the following procedure: