roVideoMode

This object allows you to configure resolution and other video output settings. The same video resolution is applied to all video outputs on a BrightSign player. Video or images that are subsequently decoded and displayed will be scaled (using the hardware scalar) to this output resolution if necessary. The JavaScript equivalent is videomodeconfiguration (see the "roVideoMode" section of the BrightScript-JavaScript Migration Guide for the equivalent methods).

Object Creation: The roVideoMode object is created with no parameters.

The roVideoMode object generates roHdmiInputChanged and roHdmiOutputChanged event objects whenever the hotplug status of the HDMI^® input or output changes.

ifVideoMode

GetScreenModes()

Returns a roArray which contains a roAssociativeArray describing each available output on your player hardware and how those outputs are configured. This method has been implemented as of BOS 9.0.15.

When calling GetScreenModes(), confirm that the HDMI array positions are valid so you don't accidentally use an undefined array. For example, if you call getscreenmodes() on a four-output player that only has one connected display, you won't get a valid return on the other outputs.

The members are:

• name: On the XC platform, the possible values are HDMI-1, HDMI-2, HDMI-3, or HDMI-4.  The number of array items depend on the number of outputs:

  • The XC2055 has two outputs, HDMI-1 and HDMI-2

  • The XC4055 has four outputs, HDMI-1, HDMI-2, HDMI-3, and HDMI-4

  • The name tells the system which output is associated with the rest of the settings in that entry within the roAssociativeArray (the order of the HDMI outputs is not important).

• video_mode: The videomode can be either:

  • A known BrightSign format videomode (for example, 1920x1080x60p)

  • A full modeline as described in Applying a Custom Resolution#ModelineFormat

  • auto which differs slightly from previous platforms. auto isn’t recommended when using multiple outputs because the canvas positions are fixed and so if a screen uses an unexpected resolution then it won’t be positioned correctly in the canvas.

• display_x and display_y: The position of the screen within the overall canvas. The origin (0,0) is the top left corner, and each screen can be positioned relative to it. This allows gaps to be left on the canvas between screens for bezel compensation.

• transform: One of normal, 90, 180 or 270 rotation. Each screen can be rotated independently. When a screen is rotated, it rotates all of the content including video. If a single screen is set to 1920x1080x60p and 90 then the screen is running in portrait mode and all of the firmware will run as if the screen is set to 1080x1920x60p with video and graphics all rotated.

• enabled: Whether the screen is enabled for output. To turn an output to off, set enabled = false. No other fields need to be set.

If you do not want to change the existing screen settings, do not enter a value for those settings.

SetScreenModes (ScreenConfigList configs)

Takes the same format as argument that GetScreenModes() returns. By default a single screen is enabled. The player uses full resolution graphics if any of the videomodes configured using SetScreenModes use the :fullres modifier. BrightAuthor:connected always sets :fullres on all of the videomodes for the XC5. See this note to understand how the x/y display coordinates works with output resolution.

This method has been implemented as of BOS 9.0 and later.

To configure two screens, enter:

To configure a 1x2 video wall with bezel compensation, enter:

In this case the resulting canvas will be 1920x2180, and full screen video and graphics will display across all outputs.

GetPerformanceMetrics

This method returns the last, peak, and average measured GPU values.

SetMode(mode As String) As Boolean 

Sets the video output mode. See here for a list of supported video modes. Calling this method causes the application to restart if the specified video mode is different from the current video mode. This method also accepts "auto" as a mode parameter, or "custom" which will use the mode configured using SetCustomModeline. The following optional parameters can be appended to the string

• <resolution>:<color_space>:<depth>bit: Sets the video profile for HDMI output. For example, to output 4Kp60 at the 4:2:0 color space with 10 bits of depth, you would pass the following string: "3840x2160x60p:420:10bit".

• <resolution>:preferred: Enables the preferred video mode setting. This instructs the player to only use the video mode if the display EDID indicates that it is supported. Otherwise, the output will default to "auto" mode. If no EDID is detected at bootup, the player will output the preferred video mode. If an HDMI hotplug event occurs afterward, then the player will perform the preferred video-mode check again. The :preferred flag currently ignores video profile settings (i.e. color space and bit depth).

• <resolution>:fullres: Enables full-resolution graphics. This instructs the player to match the graphics plane to the video mode; otherwise, video modes larger than 1920x1200 upscale the graphics plane to match the video output. See here for more details and a list of supported modes/models. If the fullres mode is used with graphics-intensive HTML applications, we recommend enabling the gfxmemlarge setting as well.

• <resolution>:gfxmemlarge: Enables the large graphics memory configuration for XTx44 and XTx43 models (at the expense of general-purpose memory). This setting requires a reboot to take effect.

• <resolution>:gfxmemdefault: Resets the graphics memory configuration to default. This setting requires a reboot to take effect.

• <resolution>:dbv: Enables Dolby Vision on video output (XTx44 only). Only one video decoder is available when Dolby Vision is enabled.

• <resolution>:rgb:<range>: Sets the color space to RGB. The optional <range> parameter can be one of the following values:

  • auto: The default setting. Over HDMI, the player will output RGB Full for VESA modes and RGB Limited for TV modes. Over DVI, the player will output RGB Full for all modes.

  • fullrange: The RGB Full (0-255) setting

  • limitedrange: The RGB Limited (16-235) setting

SetCustomModeline(roString modeline) As roBool

Sets the custom videomode with the supplied modeline (see Applying a Custom Resolution). The custom videomode can then be selected using SetMode.

GetModeForNextBoot() As String

Returns the target video mode of the device the next time it reboots. The return value is specified with the SetModeForNextBoot() method.

GetBestMode(connector As String) As String

Returns the highest video mode for this player that can be supported by the display via EDID. The video connector can be specified as "hdmi" or "vga" (these values are case sensitive). If the display does not return a resolution value over EDID (or if no display is connected), this method returns a blank string.

GetMode() As String

Returns the current video mode of the device, which is specified using the SetMode() method.

GetFailureReason() As String

Returns additional information when a member function returns false.

GetAvailableModes() As Array 

Returns all video modes supported by the player as an array of of entries. Each entry is an associative array with the following values:

• videomode string: A description of the video mode (a full list of modes can be found here)

• width int: The width of the video output

• height int: The height of the video output

• graphicsPlaneWidth int: The width of the graphics plane 

• graphicsPlaneHeight int: The height of the graphics plane

• framerate int: The frame rate of the video output

• interlaced boolean: A flag indicating whether the video output is interlaced (true) or progressive (false)

• overscan boolean: A flag indicating whether the video output is using an overscan setting or not

• colorspace string: The color space of the video signal ("rgb", "yuv420", or "yuv422")

• colordepth string: The color depth of the video signal ("8bit", "10bit", or "12bit")

• dropframe boolean: A flag indicating whether the video timecode utilizes drop frames 

• preferred boolean: A flag indicating whether the video mode is the preferred mode, which is configured using the SetMode() method

GetActiveMode() As AssociativeArray

Returns information about the current video mode as an associative array:

• videomode string: The current video mode (e.g. "3840x2160x60p")

• colordepth string: The current color depth ("8bit", "10bit", or "12bit")

• colorspace string: The current color space ("rgb", "yuv420", or "yuv422")

• preferred string: A "true" or "false" string indicating whether the current video mode is the preferred mode, which is set using the SetMode() method.

GetConfiguredMode() As AssociativeArray

Returns information about the video mode configured using the SetMode() method. This method returns an roAssociativeArray; see the GetAvailableModes() entry for more details about returned values. If the video mode is set to "auto", this method will return Invalid.

GetFPS() As Integer

Returns the current framerate of the video output.

SetDecoderMode(decoder As String, timeslice_mode As String, z_order As Integer, friendly_name As String, enable_mosaic_deinterlacer As Boolean) As Boolean 

Configures a video decoder for either standard mode or Mosaic mode. In standard mode, a single decoder is used to play a single video; in Mosaic mode, the decoder can be used to decode multiple videos from different local or remote sources. See the Selecting Decoders section below for more information on assigning video players to decoders in HTML or BrightScript.

• decoder: The video decoder to be used (decoder availability differs by model).

  • "4K": The primary 4K decoder (XTx44 models only)

  • "4K2": The secondary 4K decoder (XTx44 models only)

  • "4K": The sole 4K decoder (HDx24, XTx43, 4Kx42, XDx34, XDx33 and HDx24 models only)

  • "HD1": The primary HD decoder

  • "HD2": The secondary HD decoder

• timeslice_mode: The maximum resolution that the decoder will accept (at framerates up to 60p). If this resolution is the same as the decoder's maximum resolution limit, the decoder will use standard mode, not Mosaic mode.

  • "4K": 3840x2160

  • "HD": 1920x1080

  • "SD": 720x576

  • "CIF": 352x288

  • "QCIF": 176x144

• z_order: The z-order of the video window (in standard mode) or group of video windows (in Mosaic mode). A positive integer positions the video window(s) in front of the graphics plane, while a negative integer positions the video(s) behind the graphics plane. If there are two video decoders in use, the video window(s) of the decoder with the higher z_order value will be positioned in front. The graphics plane z-order can be modified with the roVideoMode.SetGraphicsZOrder() method, and the video decoder z-order can be modified with the roVideoPlayer.ToFront()/ToBack() methods.

• friendly_name: A human-readable name for referencing the decoder in HTML and scripts

• enable_mosaic_deinterlacer: A Boolean value indicating whether Mosaic-mode videos can be interlaced or not. Enabling the deinterlacer will allow playback of interlaced videos in Mosaic mode, but will reduce the number of Mosaic-mode videos that can be decoded simultaneously as well.

GetDecoderModes() As roArray

Returns an array of associative arrays, each one corresponding to a single decoder. Each associative array contains the following entries:

• decoder_name string: The system name of the decoder

• friendly_name string: The name of the decoder as specified when calling SetDecoderMode()

• max_decode_size string: The maximum resolution of the decoder, as set by system software. This value can be either "4K" or "HD"

• configured_decode_size string: The maximum resolution of the decoder that is specified when calling SetDecoderMode()

• mode string: The current mode of the decoder, which can be either "Regular" or "Mosaic"

• usage_count int: The number of videos currently being decoded by the decoder

• max_usage int: The maximum number of videos that can be decoded simultaneously by the decoder. The optimum max_usage limits are described below; the limit may be lower depending on a number of factors, including interlacing and frame rate.

  • 4K decoder:

    • 1 4K video

    • 2 HD videos

    • 4 SD videos

    • 8 CIF videos

    • 10 QCIF videos

  • HD decoder:

    • 0 4K videos

    • 1 HD video

    • 3 SD videos

    • 4 CIF videos

    • 5 QCIF videos

• mosaic_mode_interlace string: The current deinterlacing mode of the decoder, which can be either "Enabled" or "Disabled". This value is specified when calling SetDecoderMode().

Set3dMode(mode As Integer) As Boolean

Sets the 3D video output mode, which is specified by passing one the following parameters:

• 0: Standard mono video (default)

• 1: Side-by-side stereo video

• 2: Top-and-bottom stereo video

Screenshot(parameters As roAssociativeArray) As Boolean

Captures a screenshot of the video and graphics layer as a .jpeg or .bmp file. The screenshot is configured by passing an associative array of parameters to the method:

• filename string: The name and path of the image file that will be saved (e.g. "SD:/myscreenshots/screen.jpg"). If the specified directory does not exist, the screenshot will fail.

• width int: The width of the image file.

• height int: The height of the image file.

• filetype string: A string determining whether the image is a "JPEG" or "BMP" file type. Note that the file extension (".jpg" or ".bmp") is not appended to the filename by default and, if needed, should be included in the filename string.

• quality int: The image-quality value (between 0 and 100) of the screenshot. This parameter is set to 50 by default.

• async int: A flag that determines whether the screenshot should be taken synchronously or asynchronously. If set to 0, the function returns true  after the image file has successfully finished writing. If set to 1, the function will return true prior to saving the file, then return an roScreenShotComplete event once the file has finished writing.

• rotation int: The rotation of the screenshot image (in degrees). The default value is 0. Accepted values are 0, 90, 180, and 270.

GetResX() As Integer

Returns the current width of the graphics plane.

GetResY() As Integer

Returns the current height of the graphics plane.

GetVideoResX() As Integer

Returns the current width of the video plane.

GetVideoResY() As Integer

Returns the current height of the video plane.

GetOutputResX() As Integer

Returns the width of the display for the current video mode.

GetOutputResY() As Integer

Returns the height of the display for the current video mode.

GetSafeX() As Integer

Returns the horizontal coordinate for the upper-left corner of the "safe area". For modes that are generally displayed with no overscan, this will be zero.

GetSafeY() As Integer

Returns the vertical coordinate for the upper-left corner of the "safe area". For modes that are generally displayed with no overscan, this will be zero.

GetSafeWidth() As Integer

Returns the width of the "safe area." For modes that are generally displayed with no overscan, this will return the same as GetResX.

GetSafeHeight() As Integer

Returns the height of the "safe area." For modes that are generally displayed with no overscan, this will return the same as GetResY.

SetGraphicsZOrder(order As String) As Boolean 

Specifies the order of the graphics plane (which includes all graphical elements) in relation to the video plane(s). This method accepts three parameters:

• "front": Places the graphics plane in front of the video plane(s).

• "middle": Places the graphics plane between two video planes. This option is only applicable for models that have two video decoders (e.g. XTx44, XDx34).

•  "back": Places the graphics plane behind the video plane(s).

If the player is rendering two videos, the front and back options will always place the graphics plane in front of or behind both video planes. To determine the z-order of video planes in relation to one another, use the ToFront() and ToBack() methods provided by the roVideoPlayer object. The following table shows all possible video and graphics z-order arraignments that can be specified using the SetGraphicsZOrder() method and calling the ToFront()  and ToBack() methods on a "Video1" roVideoPlayer instance.

PauseGraphics(timeout_in_ms As Integer) As Boolean 

Suspends graphics compositor updates for the specified number of milliseconds (or until the ResumeGraphics() method is called), up to a maximum interval of 10 seconds. While the graphics compositor is paused, no visual elements will be updated (except for HWZ video, scrolling tickers, and off-screen Chromium textures). Use this method to combine Show(), Hide(), Raise(), Lower(), and SetRectangle() operations into a single v-sync update.

ResumeGraphics() As Boolean

Resumes the graphics compositor if it has been paused with the PauseGraphics() method.

SetImageSizeThreshold(parameters As roAssociativeArray) As Boolean 

Changes the maximum allowed size for images. Images sizes are measured in bytes using the following formula: image_width * image_height * 4.

The default image size limit is 35389440 bytes (equivelant to 3840x2160x32bpp) for XTx44, XTx43, XDx34, XDx33, and 4Kx42 models and 2621440 bytes (equivelant to 2048x1280x32bpp) for other models. Displaying images larger than the default value may deplete the graphics memory and cause a crash, so we recommend testing a script that uses this method thoroughly before deploying it in a production environment. This method accepts an associative array with the following parameters:

• width int: The image width value

• height int: The  image height value

• ignore int: A flag specifying whether the image size limit is enabled (0) or disabled (1)

AdjustGraphicsColor(parameters As roAssociativeArray) As Boolean

Adjusts the video and graphics output of the player using the following parameters, which can be passed to the method as an associative array: "brightness", "hue", "contrast", "saturation". Each parameter has a default value of 0 and can accept a range of values between -1000 and 1000.

ConfigureHdmiInput(parameters As roAssociativeArray) As Boolean

Configures EDID reporting for the HDMI input. By default, the input EDID includes video modes from the display attached to the HDMI output, some video modes supported by the player, and support for PCM audio up to 48kHz; it does not report proprietary media codecs that can be decoded by the device connected to the HDMI output, so you can use this method to announce such support if available at the endpoint. Using this method to change the default configuration will trigger a reboot on the player.

The passed associative array can contain the following parameters:

• MaxHdcpVersion int: The maximum supported version of HDCP advertised by the HDMI input. The default value is 2, which indicates support for HDCP 2.2. It can also be set to 1, which limits advertised support to HDCP 1.4.

• MaxSampleRate int: The maximum supported PCM audio sampling rate in Hz (e.g. the default sampling rate is 48000)

• MaxChannelCount int: The number of PCM channels that are advertised over EDID. The default value is 2, which allows for stereo mixdown. Increasing this value to 6 allows the source to send multichannel PCM. If AC-3 or E-AC-3 is enabled on the player, multichannel audio is supported regardless of the MaxChannelCount setting. 

• EnableAC3 int: A flag specifying whether AC-3 is not supported (0) or supported (1)

• EnableEAC3 int: A flag specifying whether E-AC-3 is not supported (0) or supported (1)

• EnableTrueHDMlp int: A flag specifying whether TrueHD MLP is not supported (0) or supported (1)

• EnableDTS int: A flag specifying whether DTS is not supported (0) or supported (1)

• EnableDTSHD int: A flag specifying whether DTS-HD is not supported (0) or supported (1)

• LockAudioToVideoClock int: A flag specifying whether the audio sample rate clock is locked to the audio clock (0) or video clock (1) of the incoming HDMI signal.

• EdidFilename string: Allows a valid EDID filename to be passed to the HDMI input (if the filename is not valid, it will be rejected and an error will appear in the log). In the example below, the HDMI input will be configured with the EDID from edid.bin on bootup:

SetHdmiMetadata(parameters As roAssociativeArray) As roAssociativeArray

Configures strings to be sent in the HDMI metadata. This method accepts an associative array with the following parameters:

• spd_vendor string: The vendor string

• spd_description string: The description string

This method returns an associative array, which can contain a single parameter:

• restart_required boolean: A flag indicating whether the player must be rebooted for the metadata changes to take effect

GetHdmiOutputStatus() As roAssociativeArray

Returns an associative array of Boolean and integer values if an HDMI output is currently connected to a display device. This method will return Invalid if the HDMI output is currently not connected to a display device. The associative array contains the following parameters:

• output_present boolean: A flag indicating wheter the HDMI output is connected to a display device

• output_powered boolean: A flag indicating whether the display device is on (i.e. RX powered)

• EOTF string: A string indicating the current electro-optical transfer function (EOTF) used by the display. The following are possible values:

  • "HDR (GAMMA)"

  • "SDR (GAMMA)"

  • "SMPTE 2084 (PQ)"

  • "HLG"

  • "unspecified"

• audio_bits_per_sample int: The number of bits per audio sample

• audio_format string: The format of the audio output. A "PCM" value indicates that the player is sending decoded output.

• audio_channel_count int: The number of audio channels in the output

• audio_sample_rate int: The audio sample rate (in hertz)

GetHdmiInputStatus() As roAssociativeArray

Returns an associative array of Boolean and integer values if an HDMI input is currently connected to the device. This method will return Invalid if there is currently no HDMI input source. The associative array contains the following parameters:

• device_present boolean: A flag indicating whether an HDMI input source is present

• width int: The width of the source video

• height int: The height of the source video

• interlaced boolean: A flag indicating whether the video source is interlaced

• frame_rate float: The framerate of the source video

• pixelClock float: The pixel-clock rate of the source video (in MHz)

• colorspace string: The color space of the source video

• audio_type string: The audio encoding of the source video

• audio_sampling_rate int: The audio sampling rate of the source video (in Hz)

GetCompositorCrc() As Integer

Returns the CRC of the Y and Cb signals as a single integer.

GetTxHdcpStatus() As roAssociativeArray

Returns an associative array indicating the current HDCP status of the HDMI output. The associative array currently contains a single key labeled state, which can have the following values:

• "not-required": HDCP is not required by the player. HDCP is required by the player if the video has been decoded locally and needs protection or if the script has called the forceHdcpOn() method. Note that, even if the "not-required" value is returned, HDCP might still be active in passthrough mode if an upstream HDMI source (i.e. a device connected to the HDMI input port on the player) has requested it.

• "authenticated": HDCP has been enabled and successfully negotiated.

• "authentication-in-progress": HDCP has been enabled, but authentication has not been completed.

• "authentication-failed": HDCP has been requested but could not be negotiated.

ForceHdcpOn(force As Boolean) As Boolean

Forces HDCP authentication on the HDMI output if passed True. Passing False to this method will prevent forced authentication attempts with subsequent hotplug events. This method will return False if the player does not support HDCP or if ForceHdcpOn() has already been called with the same value.

DisableHdcpRepeater(disable As Boolean) As Boolean

Prevents HDCP authentication from taking place on the HDMI input if passed True. The HDMI source will treat the player like any other non-HDCP authenticated HDMI sink. This method returns False if the HDCP state could not be changed, indicating that there's no HDMI input on the player or that HDCP has already been disabled.

SetBackgroundColor(color As Integer) As Boolean

Specifies the background color using an #rrggbb hex value (8 bits for each color). Hex codes like #ffffff will cause an autorun error, so you should use the decimal of hex code (for example, the decimal of #ffffff is 16777215). You can get this value from a hex to decimal converter website: Hexadecimal / Decimal Colors.

SetPowerSaveMode(power_save_enable As Boolean) As Boolean

Disables HDMI output, the syncs for VGA output, and the DAC output for component video. The absence of a signal will cause some monitors to go into standby mode.

IsAttached(connector As String) As Boolean

Returns True if the specified video connector is attached to an output device (i.e. the display EDID can be read successfully). This method can be passed the following parameters (note that they are case sensitive):

• "hdmi"

• "vga"

HdmiAudioDisable(disable As Boolean) As Boolean

Disables audio output if True. This method is set to False by default.

SetMultiscreenBezel(x_pct As Integer, y_pct As Integer) As Boolean

Adjusts the size of the bezel used in calculations for multiscreen displays, allowing for users to compensate for the width of their screen bezels. The calculations for the percentages are as follows:

x_percentage = (width_of_bezel_between_active_screens / width_of_active_screen) * 100

y_percentage = (height_of_bezel_between_active_screens / height_of_active_screen) * 100

The bezel measurement is therefore the total of the top and bottom bezels in the y case, or the left and right bezels in the x case. When this value is set correctly, images spread across multiple screens take account of the bezel widths, leading to better alignment of images.

SaveEdids(filename As String) As Boolean

Saves the EDID information of the display(s) connected via HDMI and/or VGA. The EDID fields are saved sequentially as raw binaries into the specified file. The EDID sets are two 2kb each, resulting in a maximum file size of 4kb. This method returns True upon success and False upon failure.

GetEdidIdentity(video_connector As Boolean) As roAssociativeArray

Returns an associative array with EDID information from a compatible monitor/television. Passing True with this method specifies EDID over HDMI, while passing False specifies EDID over VGA. These are the possible parameters returned in the associative array:

• serial_number_string

• year_of_manufacture

• monitor_name

• manufacturer

• text_string

• serial_number

• product

• week_of_manufacture

• unstable

The system will generate an roHdmiEdidChanged event when an HDMI cable is hotplugged and the EDID information changes. Calling GetEdidIdentity(true) at this point retrieves the new EDID information.

SetMpcdi(parameters As roAssociativeArray) As Boolean

Enables MPCDI using the passed parameters. See the MPCDI tech note for more information about configuring MPCDI on BrightSign players.

SetSyncDomain(domain As String) As Boolean 

Enables Genlock synchronization on the specified roSyncManager domain. To disable Genlock on the domain, pass an empty string to this method. To reconfigure an active Genlock synchronization, call SetSyncDomain() again using the domain name of the new or edited roSyncManager instance.

ifMessagePort

SetPort(port As Object) As Void

Posts events to the attached message port

ifUserData

SetUserData(user_data As Object)

Sets the user data that will be returned when events are raised.

GetUserData() As Object

Returns the user data that has previously been set via SetUserData(). It will return Invalid if no data has been set.

"Auto" Video Mode 

If the video mode is set to "auto," the BrightSign player will use the following algorithm to determine the best video mode to use based on connected hardware:

1. Try HDMI: If HDMI is attached, use the highest-resolution mode (as reported by the monitor) that the player supports.

2. Default to 640x480x60p.

3. If an HDMI hotplug event occurs at any point, recheck the monitor EDID to determine if the highest-resolution mode has changed. If it has changed, reboot the player and use the new video mode.

Selecting Decoders for Playback 

The system software selects which video decoder to use based on the resolution probed from the video file. In standard mode, it will attempt to select the decoder that has the closest maximum supported resolution (i.e. 1920x1080 for the HD decoder and 3840x2160 for the 4K decoder), without exceeding that maximum resolution. If a decoder has been configured for Mosaic mode, it will match the video resolution against the specified timeslice_mode instead. If both decoders support the same maximum resolution, you can select a decoder by matching the z-order of the roVideoPlayer instance (set using the ToFront() and ToBack() methods) with the z-order of the decoder (set using the roVideoMode.SetDecoderMode() method).

You can also select the decoder manually. First, configure the decoder(s) using the roVideoMode.SetDecoderMode() method. Then, use the friendly_name specified when calling the method to designate a decoder to use for video playback.

To select a decoder in BrightScript, pass an associative array to the roVideoPlayer.PlayFile() method containing the decoder:[friendly_name] parameter:

To select a decoder for HTML video, include the decoder:[friendly_name] property with the hwz attribute:

The max_usage of a decoder determines how many video players can be assigned to the decoder using the system software algorithm described above—video players beyond the  max_usage limit may be assigned to another decoder or not displayed at all. On the other hand, if you manually assign video players using the friendly_name of the decoder, you can assign more video players to the decoder than the max_usage limit, but this may cause unpredictable video-display behavior.