[mythtv] CalcReadAheadThresh always the same. Bug or feature ?

[John]

I have been trying to trace down problems with playing BBC HD, and came 
across the following behavior. I was trying to find out if the BBC 
bitrate being reported / picked up wrong was the problem, and noticed 
the behavior below.

Behavior is the same in SVN 13502 13528 and 13755.

BBC1 - SD

Input #0, mpegts, from 'myth://192.168.254.4:6543/17306_20070623235642.mpg':
  Duration: N/A, bitrate: 15256 kb/s
  Stream #0.0[0x91a], 1/90000: Video: mpeg2video, yuv420p, 720x576, 
1/25, 15000 kb/s, 25.00 fps(r)
  Stream #0.1[0x91b](eng), 1/90000: Audio: mp2, 48000 Hz, stereo, 256 kb/s
  Stream #0.2[0x91c](eng), 1/90000: Data: 0x0000

2007-06-23 23:56:43.378 
RingBuf(myth://192.168.254.4:6543/17306_20070623235642.mpg): 
CalcReadAheadThresh(3063884464 KB)
                         -> threshhold(64 KB) min read(0 KB) blk size(32 KB)


Astra HD

Input #0, mpegts, from 'myth://192.168.254.4:6543/64003_20070624000216.mpg':
  Duration: N/A, bitrate: 22255 kb/s
  Stream #0.0[0x85], 1/90000: Video: mpeg2video, yuv420p, 1920x1088, 
1/25, 21999 kb/s, 25.00 fps(r)
  Stream #0.1[0x86](eng), 1/90000: Audio: mp2, 48000 Hz, stereo, 256 kb/s

2007-06-24 00:02:22.593 
RingBuf(myth://192.168.254.4:6543/64003_20070624000216.mpg): 
CalcReadAheadThresh(3063884464 KB)
                         -> threshhold(64 KB) min read(0 KB) blk size(32 KB)

BBC HD (Also reports wrong rawbitrate)

Input #0, mpegts, from 'myth://192.168.254.4:6543/13940_20070624000309.mpg':
  Duration: N/A, bitrate: 640 kb/s
  Stream #0.0[0x90e], 1/90000: Video: h264, yuv420p, 1440x1080, 1/25, 
500 kb/s, 25.00 fps(r)
  Stream #0.1[0x910](NAR), 1/90000: Audio: mp2, 48000 Hz, stereo, 256 kb/s
  Stream #0.2[0x911](eng), 1/90000: Data: 0x0000
  Stream #0.3[0x90f](eng), 1/90000: Audio: ac3, 48000 Hz, stereo, 384 kb/s


2007-06-24 00:03:22.318 
RingBuf(myth://192.168.254.4:6543/13940_20070624000309.mpg): 
CalcReadAheadThresh(3063884464 KB)
                         -> threshhold(64 KB) min read(0 KB) blk size(32 KB)

Is the estbitrate / rawbitrate wrong, or is this setting of the 
threshold irrelevent to the setting of the buffer. I had assumed the 
buffering to increase with bitrate from looking at the code and the list 
archives ?


John