[Flac-dev] mid-side coding and bits per sample

[Eri Eri]

Dear list,

i'm doing a bit of analisys on flac's source code and i've run into something i can't quite grasp.

flac version 1.2.1

flaclib C

stream_encoder.c

function "process_subframes_"

line 2999

++++++++++++++++++++++
    if(do_mid_side) {
        FLAC__ASSERT(encoder->protected_->channels == 2);
        for(channel = 0; channel < 2; channel++) {
            const unsigned w = get_wasted_bits_(encoder->private_->integer_signal_mid_side[channel], encoder->protected_->blocksize);
            encoder->private_->subframe_workspace_mid_side[channel][0].wasted_bits = encoder->private_->subframe_workspace_mid_side[channel][1].wasted_bits = w;
            encoder->private_->subframe_bps_mid_side[channel] = encoder->protected_->bits_per_sample - w + (channel==0? 0:1);
        }
    }
++++++++++++++++++++++++

In that piece of code the encoder determines how many wasted bits there are in each channel (mid-side) and calculates effective BPS for each of them. What i don't understand is why it should add one bit to the BPS of the side channel "(channel==0? 0:1)", eventhough there is no "correction" to wasted bits. Could someone shed light on this?
Thank you very much in advance!
 		 	   		  
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