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Configuration_Video.md

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This section explains how to use settings related to the video.

Bandwidth and congestion control

There are two kinds of video bandwidths: upload and download.

Upload: Bandwidth (kbps) used by the video stream (RTP + RTCP) from the MCU to a single endpoint.

Download: Bandwidth (kbps) used by the video stream (RTP + RTCP) from the one endpoint to the MCU. This user-defined value will be forwarded to the remote endpoint using the SDP and RTCP-REMB and it’s up to this one to respect it or not. For more technical information, check here.

The configuration file allows setting the maximum upload and download bandwidths to use. If these values are undefined then, the upload bandwidth is computed following this formula:

video-max-upload-bandwidth (kbps) = ((video-width * video-height * video-fps * motion-rank * 0.07) / 1024)

For example, 720P video stream @15 frames per second with medium (2) motion rank will consume 12807201520.07 = 1935360 bps = ~1890 kbps unless video-max-upload-bandwidth entry is defined.

Congestion-ctrl-enabled = yes
video-max-upload-bandwidth = -1 # in kbps, <=0 means undefied
video-max-download-bandwidth = -1 # in kbps, <=0 means undefied
video-motion-rank = 2 # 1(low), 2(medium) or 4(high)
video-fps = 15 # [1 - 120]

Configuration 12: Setting video bandwidth and congestion control

  • Congestion-ctrl-enabled – whether to enable draft-alvestrand-rtcweb-congestion-03 and draft-alvestrand-rmcat-remb-01. Check here for more information.
  • video-max-upload-bandwidth - defines the maximum bandwidth (kbps) to use for outgoing video stream (per endpoint). If congestion control is enabled then, the bandwidth will be updated based on the network conditions but these new values will never be higher than what you defined in your configuration file
  • video-max-download-bandwidth - defines the maximum bandwidth (kbps) to use for incoming video stream (per endpoint). If congestion control is enabled then, the bandwidth will be updated based on the network conditions but these new values will never be higher than what you defined in your configuration file
  • video-motion-rank - defines the video type. Supported values: 1 (low, e.g. home video security systems), 2 (medium, e.g conference call) or 3 (high, e.g. basketball game).
  • video-fps - defines the video framerate for the mixed stream regardless the input fps. Supported values: [1 – 120].
  1. To check available bandwidth: http://www.speedtest.net/
  2. To check bandwidth usage: iftop.

Output size, pixel aspect ratio and letterboxing

The output (MCU → endpoints) mixed video size is independent of the input sizes (from the endpoints). video-mixed-size configuration entry is used to set the preferred value.

Accepted values are:

  • sqcif(128x98)
  • qcif(176x144)
  • qvga(320x240)
  • cif(352x288)
  • hvga(480x320)
  • vga(640x480)
  • 4cif(704x576)
  • svga(800x600)
  • 480p(852x480)
  • 720p(1280x720)
  • 16cif(1408x1152)
  • 1080p(1920x1080)
  • 2160p(3840x2160) If no value is defined then, the mixed video size is assumed to be equal to vga (640x480). 720p, 1080p and 2160p are commonly named HD, Full HD and Ultra HD.
video-mixed-size = vga

Configuration 13: Setting output mixed video size

In this beta version, it’s not allowed to set arbitrary values because of backward compatibility. The final version will probably allow this.
To draw the speaker and listeners video on the output mixed video we need to resize these frames to feet the destination. The video frames are linearly resized following a specific Pixel Aspect Ratio (PAR) before being letterboxed.

video-speaker-par = 0:0
video-listener-par = 1:1

Configuration 15: Setting Pixel Aspect Ratio
A PAR equal to 1:1 means “skip the linear resizing” and a value of 0:0 means “skip both linear resizing and letterboxing”.
Common PAR values: 1:1, 16:9 or 4:3.

Jitter Buffer

video-jb-enabled configuration entry is used to enable or disable video jitter buffer. It's highly recommended to enable video jitter buffer because it's required to have RTCP-FB (NACK, FIR, PLI... as per RFC 5104) fully functional. Enabling video jitter buffer gives better quality and improves smoothness. For example, no RTCP-NACK messages will be sent to request dropped RTP packets if this option is disabled. It’s also up to the jitter buffer to reorder RTP packets. For more technical information, check here.

video-jb-enabled = yes # no to disable

Configuration 14: Enabling or disabling video jitter buffer

Zero-artifacts

It’s up to the MCU to decode all video streams from the endpoints, mix them before sending the result. If RTP packets are lost on one stream then, artifacts will be introduced on the mixed frame (result). Enabling zero-artifact feature fix this issue. There are some requirements on the endpoints to have this feature fully functional. For more technical information, check here.

video-zeroartifacts-enabled = yes # no to disable

Configuration 15: Enabling or disabling zero-artifact

Mixing type

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Overlays

The configuration file allows managing the overlays (font size and type, position, watermark…).

overlay-fonts-folder-path = ./fonts/truetype/freefont
overlay-copyright-text = Doubango Telecom
overlay-copyright-fontsize = 12
# full path: ./fonts/truetype/freefont/FreeSerif.ttf
overlay-copyright-fontfile = FreeSerif.ttf
overlay-speaker-name-enabled = yes
overlay-speaker-name-fontsize = 16
# full path: ./fonts/truetype/freefont/FreeMonoBold.ttf
overlay-speaker-name-fontfile = FreeMonoBold.ttf
overlay-speaker-jobtitle-enabled = yes
overlay-watermark-image-path = ./images/logo35x34.jpg

Configuration 16: Video overlays

  • overlay-fonts-folder-path - defines the base folder path where to look for the font types. The default fonts come from ftp://ftp.gnu.org/pub/gnu/freefont. For more fonts (not free), we recommend http://www.dafont.com/.
  • overlay-copyright-text - defines the copyright text to display on the mixed video. Comment the line to disable this feature.
  • overlay-copyright-fontsize - defines the font size to use to draw the copyright text.
  • overlay-copyright-fontfile - defines the font file to use to draw the copyright text on the mixed video. The full path to the TruType file will be ‘overlay-fonts-folder-path+"/"+overlay-copyright-fontfile’.
  • overlay-speaker-name-enabled - whether to draw the speaker's name on the mixed video.
  • overlay-speaker-name-fontsize - defines the font size to use to draw the speaker's name (and job title) on the mixed video.
  • overlay-speaker-name-fontfile - defines the font file to use to draw the speaker's name on the mixed video. The full path to the TruType file will be ‘overlay-fonts-folder-path+"/"+overlay-speaker-name-fontfile’.
  • overlay-speaker-jobtitle-enabled - whether to draw the speaker's job title on the mixed video.
  • overlay-watermark-image-path - defines the full path to the image to use to watermark the mixed video. Comment the line to disable this feature.

For more technical information, check here.

To test test the overlays we highly recommended using the WebRTC Telepresence client.

Patterns

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