Measurements of Cut-off Frequency and Avarage Bit Rate of OggVorbis RC3 Encoder


OggVorbis RC3 has been released, in which VBR encoding quality is uniquely specify by -q n values.
Once q value is set, cut-off frequency of LPF is determined internally, indicating that no one knows
cut-off frequency explicitly.
In addition, the avarage bit rate can't see until the encoding has started.
Just for user's reference, cut-off frequency and avarage bit rate are mesured as function of -q value.


[Experimental]
A 10 sec white noise .wav file is generated from CoolEdit Pro(v1.2) as an original.
The original is encoded to .ogg file, decoded to .wav by using Sound Player Lilith(v.988a), and
the resultant .wav is analyzed by WaveSpectra(v1.20).
White noise has almost flat frequency responce in audio frequency range, as shown in Fig 1.
The frequency responce taken with -q 0.00(,cut-off 15,068Hz, 75.1kbps) is shown in Fig 2.



   Fig 1 Frequency responce of original white nose (44.1kHz, 16bit, dual mono)

   Green shows actual wave, and red is the peak hold value.





   Fig 2 Frequency responce of q=0.0 (avarage bit rate 75.1kbps)



[Results]