NCast Telepresenter Reference Manual
Sometimes a media file is placed on a web server and is played without the assistance of a streaming
server. In such instances the location of the media data required for progressive download needs to be
optimized. Optimization rearranges the audio and video blocks within the file. Optimization does not
significantly affect the size of a file, but adds slightly to the post-Session processing time required. Uncheck
this box if files will not be used in progressive download environments.
4.3.10. Transcode Timing
The time needed to transcode files to other formats and resolutions depends on several different factors.
For an XGA-sized image on an M4 using these settings:
•
Video - MPEG-4, 1024x768, 30 fps, 5000 kbps
•
Audio - AAC 44100Hz, Mono, 64 kbps
•
1 hour recording
the transcoding times to H.264 were measured as follows:
•
1024x768 - 55-48 minutes
•
640x480 - 41-38 minutes
•
320x240 - 26-25 minutes
Four different bitrates were used (from 4000 Kbps to 125 Kbps). The higher resulting values are for higher
bitrates, and the lower values are for lower bitrates. The bitrate doesn't impact transcode time very much.
The transcode time is influenced mainly by the video size and framerate.
For 1920x1080 transcodes these settings were used:
•
Video - MPEG-4, 1920x1080, 30 fps, 5000 kbps
•
Audio - AAC 44100 Hz., Mono, 64 kbps
•
1 hour recording
Transcoding times to H.264:
•
1920x1080 - 142-124 minutes
•
1280x720 - 109-101 minutes
•
640x360 - 53-51 minutes
Transcoding times to Theora are quite lengthy because this first generation implementation has not yet been
optimized as much as some of the more mature codecs.
4.4. C
HANNEL
S
ETTINGS
- L
AYOUT
4.4.1.
Frame Size
The Frame Size defines the dimensions of the Frame, a surface (capture surface or “the canvas”) which is
the primary imaging surface on which the composite image (Main PIP Overlays) is
drawn. The resolution and aspect ratio of the transmitted or archived media stream aligns exactly with the
resolution and aspect ratio of the Frame. Consequently, selection of one of the default frame sizes and
aspect ratios, or definition of a custom Frame Size and possibly a custom Aspect Ratio is the first step in
defining the format of the media stream which will be produced by the Telepresenter. The Frame can have
any dimension or aspect ratio, with the limitation that the maximum dimensions are 1920 x 1200.
Once the frame is defined, the next step is the (X,Y) placement and (W,H) sizing of the primary or “Main”
image stream. Typically the “Main” stream is sized at “Full-screen” which means that the primary stream is
scaled to the full dimensions of the frame. It is useful to note, however, that the primary stream can be
dimensioned to a smaller size than the full frame size. The unused space might then be reserved for the
secondary image stream (the PIP image, but placed outside the boundaries of the Main image) and possibly
NCast Corporation
Revision 2.2
Page 54
