@nurbs, I agree with you. Some info:
The bsi (Bit Stream Information) is the part of header with fields like:
bsid
bsmod
acmod
if((acmod & 0x1) && (acmod != 0x1)) /* if 3 front channels */ {cmixlev}
if(acmod & 0x4) /* if a surround channel exists */ {surmixlev}
if(acmod == 0x2) /* if in 2/0 mode */ {dsurmod}
lfeon
dialnorm
...
The fields cmixlev and surmixlev can indicate the coeficients to mix the center and surround channels to obtain a stereo audio.
@OvejaNegra
I never see others values than default in these fields, I think is better ignore them.
The mix (dpl2) used by eac3to is:
L' = 0.5 x L + 0.3535 x C + 0.433 x SL + 0.25 x SR
R' = 0.5 x R + 0.3535 x C - 0.25 x SL - 0.433 x SR
only options -mixlfe (use LFE in mix) -phaseShift(+-90º for SL-SR) can be used.
eac3to is a transcoder, and not a player, for HD audio then the option to apply the DRC or DialNorm isn't considered.
You can safely use BeLight (BeSweet) for your both purposes.
Dialog Normalization:
Was an obsolete attempt to normalize the sound volume to avoid change the volume button in audio equipment. Assume than the normal dialog volume is -31dB, then if the value of this field in BSI is -27dB make a -4dB attenuation to all channels in the stream.
Like only Ac3 uses this value, instead solve a problem make all ac3 streams to low volume compared with TV commercials, CDAudio, mp3 and so on. The best option is put -31dB then decoders don't attenuate the signal.
Sorry also for my english, if you don't understand me, you can use the
spanish Doom9 forum