Hi Dan,
I am a senior research scientist at RealNetworks that has been involved in
creating RealVideo since day 1. We take our customers concerns and critical
comments very seriously as we strive to create the highest quality Internet
video experience for our clients.
One of the features of the RealProducer and RealProducer Plus was to
simplify the encoding process. We wanted to hide advanced options that
could lead to a less than compelling end-user experience. However, we tried
to balance this by offering, to the sophisticated encoding customer, the
ability to alter various settings, e.g. video/audio/total streaming bit
rate, maximum encoded frame rate, choice of audio compression, smoothest vs
sharpest vs normal video compression modes, etc.
To address some of your issues:
(1) Like NetShow, our encoder is a variable frame rate compression engine.
One can't set the frame rate, because the frame rate is choosen by the
compression engine as a function of the complexity of the content, the
physical size of the content, and the requested bit rate. The
content-creator, however, can set which mode he/she would like to encode
(high frame rate or high spatial quality) and the _maximum_ encoded frame
rate. At high bit rates, the variable frame rate algorithm will typically
result in a constant frame rate at the maximum requested frame rate.
(2) To explain why the created file sizes are not what you might have
expected, I need to explain how streaming video over a finite capacity
channel works. Like NetShow, our player must pre-buffer data before
actually displaying the content. The pre-buffering of data allows us to
momentarily, throughout playback, exceed the finite capacity channel. We
need to exceed the channel capacity in order to send I-frames, frames which
allow random access, seekability, error resiliency, etc. So when one takes
into account the pre-buffering time, the streaming bit rate of the file is
exact!
(3) I'm not sure why changing the factory settings had no effect. It
appeared on your web site that you used 5.0K audio with 145K video which
must have involved a change to our default settings. The effect with max
frame rate would only be effective if you changed it less than 10 fps. The
variable rate control algorithm at 150Kbps gave roughly 10fps playback
throughout. Consequently, making max frame rate less than this average
would produce a noticeable improvement in spatial quality at the expense of
a lower frame rate.
With playback from local disk, I've notice that some high bitrate content
stutters in the first couple of seconds of playback. This is a bug which we
are fixing. However, I've not seen this behaviour with playback from a
server. With regard to your web site, I didn't notice any frame dropping
and/or stuttering on playback. Infact, in comparing the playback statistics
of the RealPlayer and NetShow, you will find a much higher frame rate
experience thoughout playback with the Real Player. One particularly
noteworthy feature is our ability in the Player to Frame-Rate-Upsample. We
actually display a higher frame rate than the encoded source by judiciously
performating temporal interpolation between frames.
I hope this has clarified some of the issues you have experienced.
Additionally, you might want to download our free basic G2 server. This
will improve the quality of experience to all end-users.
If you have any questions, please do not hesitate to email me.
Regards,
Dr. Gary S. Greenbaum
Senior Research Scientist
RealNetworks, Inc.
Seattle, WA 98101
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