Net-X -Code, videoQC, and Net-X-Copy provide a number of overlays you can superimpose on the video output. These can be enabled or disabled using various MediaCmd commands, which are detailed in this article. 
Here are the basic MediaCmd commands:
/**
* Enable/Disable the overlay entirely
* <BR>
* \li cmdType::ctSetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
*
* \li cmdType::ctGetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <HR>
*/
gsOverlayEnable = 111000,
http://127.0.0.1:500/VVWXMLMediaCmd?setvalue&cmdalt=OverlayEnable&position=1
To select what you want to display as a string:
overlay=ovcaptions,ovaudiometers&ovcaptionsource=cc1
This can added to the source file string, like:
srt://13.64.58.80:8033?mode=caller&overlay=ovcaptions&ovcaptionsource=cc1.
or the GS_VALUE
or overlay=ovcaptions,ovaudiometers&ovcaptionsource=1 (GS_CC_CC1)
Using the gsCommands through the webRTC port:
gsOverlayCC = 111003
position = 0 disable/1 enable
start = CC source (#GS_CC_DISABLE, #GS_CC_CC1, etc.)
http://192.168.100.224:1080/netx?request=set&client=192.168.100.224&group=8&channel=0&command=start&source=srt://13.64.58.80:8033?mode=caller&overlay=ovcaptions,ovaudiometers&ovcaptionsource=cc1&target=webrtc://0.0.0.0:5001
/**
* Enable/Disable the Audio Meter Overlay
* <BR>
* \li cmdType::ctSetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
* <BR> MEDIACMD::dwAudioChannels = total audio channels to display
*
* \li cmdType::ctGetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
* <BR> MEDIACMD::dwAudioChannels = total audio channels to display
* <HR>
*/
gsOverlayAudioMeters, 111001
http://127.0.0.1:500/VVWXMLMediaCmd?setvalue&cmdalt=OverlayAudioMeters&position=1
/**
* Enable/Disable the V-Chip overlay
* <BR>
* \li cmdType::ctSetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
*
* \li cmdType::ctGetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <HR>
*/
gsOverlayVChipEnable, 111002
http://127.0.0.1:500/VVWXMLMediaCmd?setvalue&cmdalt=OverlayVChipEnable&position=1
/**
* Closed caption overlay setup
* <BR>
* \li cmdType::ctSetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::dwStart = CC source (#GS_CC_DISABLE, #GS_CC_CC1, etc)
*
* \li cmdType::ctGetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::dwStart = CC source (#GS_CC_DISABLE, #GS_CC_CC1, etc)
* <HR>
*/
gsOverlayCC, 111003
http://127.0.0.1:500/VVWXMLMediaCmd?setvalue&cmdalt=OverlayCC&position=1&start=1
/**
* Enable/Disable the Timecode overlay
* <BR>
* \li cmdType::ctSetValue
* <BR> MEDIACMD::dwPosition = 0 disable, GS_TCSOURCE_LTC/GS_TCSOURCE_VITC enable
* <BR> MEDIACMD::lSpeed = 0..16 Timecode Size
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
*
* \li cmdType::ctGetValue
* <BR> MEDIACMD::dwPosition = 0 disable, GS_TCSOURCE_LTC/GS_TCSOURCE_VITC enable
* <BR> MEDIACMD::lSpeed = 0..16 Timecode Size
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
* <HR>
*/
gsOverlayTimeCode, 111004
http://127.0.0.1:500/VVWXMLMediaCmd?setvalue&cmdalt=OverlayTimeCode&position=1&start=100&end=200
/**
* Enable/Disable the watermark
* <BR>
* \li cmdType::ctSetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::lSpeed = Opacity
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
* <BR> MEDIACMD::arbID = path to watermark
*
* \li cmdType::ctGetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::lSpeed = Opacity
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
* <BR> MEDIACMD::arbID = path to watermark
* <HR>
*/
gsOverlayWatermark, 111005
http://127.0.0.1:500/VVWXMLMediaCmd?setvalue&cmdalt=OverlayWatermark&position=1
/**
* Enable/Disable source format
* <BR>
* \li cmdType::ctSetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
*
* \li cmdType::ctGetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
* <HR>
*/
gsOverlaySourceFormat, 111006
http://127.0.0.1:500/VVWXMLMediaCmd?setvalue&cmdalt=OverlaySourceFormat&position=1
/**
* Enable/Disable custom text element
* <BR>
* \li cmdType::ctSetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::lSpeed = 0..10 for text element
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
* <BR> MEDIACMD::arbID = String
*
* \li cmdType::ctGetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::lSpeed = 0..10 for text element
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
* <BR> MEDIACMD::arbID = String
* <HR>
*/
gsOverlayCustomText, 111007
http://127.0.0.1:500/VVWXMLMediaCmd?setvalue&cmdalt=OverlayCustomText&position=1&clipid=sometext
/**
* Enable/Disable vectorscope overlay
* <BR>
* \li cmdType::ctSetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::lSpeed = Size
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
*
* \li cmdType::ctGetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::lSpeed = Size
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
* <HR>
*/
gsOverlayVectorScope, 111008
http://127.0.0.1:500/VVWXMLMediaCmd?setvalue&cmdalt=OverlayVectorScope // Not yet
/**
* Enable/Disable waveform overlay
* <BR>
* \li cmdType::ctSetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::lSpeed = Size
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
*
* \li cmdType::ctGetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::lSpeed = Size
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
* <HR>
*/
gsOverlayWaveform, 111009
http://127.0.0.1:500/VVWXMLMediaCmd?setvalue&cmdalt=OverlayWaveform // Not yet
/**
* Enable/Disable histogram overlay
* <BR>
* \li cmdType::ctSetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::lSpeed = Size
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
*
* \li cmdType::ctGetValue
* <BR> MEDIACMD::dwPosition = 0 disable/1 enable
* <BR> MEDIACMD::lSpeed = Size
* <BR> MEDIACMD::dwStart = X location
* <BR> MEDIACMD::dwEnd = Y location
* <HR>
*/
gsOverlayHistogram, 111010
http://127.0.0.1:500/VVWXMLMediaCmd?setvalue&cmdalt=OverlayHistogram // Not yet
