[gstreamer-bugs] [Bug 619548] qtdemux: Guess bitrate if only one stream's bitrate is unknown

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=619548
  GStreamer | gst-plugins-good | unspecified

--- Comment #2 from Arun Raghavan <arun at accosted.net> 2010-05-31 17:47:14 UTC ---
As a reference for how far off this patch can be, I have a sample H.263 +
AMR-NB stream with the following parameters:

System bitrate (video size/duration): ~26304.5 bps
H.263 avg. bitrate (from header): 10250 bps
H.263 max. bitratE (from header): 26634 bps
AMR-NB bitrate (guessed): 16838 bps
AMR-NB bitrate (actual) 4750 bps

So because of the high variance of the video bitrate, the estimated bitrate was
>3x the actual bitrate.

This particular instance will be solved by the more accurate AMR bitrate
estimation in qtdemux that I will be submitting soon.

In the general case. the bitrate estimation is necessarily going to be
inaccurate at times, which could be misleading. I am wondering if it might not
be better to use an "estimated-bitrate" tag, or some such when we're not sure.
It would also be useful for other cases too, such as baseparse where we guess
the bitrate by taking a running average on the stream and thus can get wildly
inaccurate initial estimates. On the flip side, this requires that clients need
to figure out which to look for, based on the application and what its accuracy
requirements are.

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