Earlier in the week I remarked on the the live Pink Floyd release, ‘Pulse’, on DVD. You may recall that this has the surround soundtrack in two formats: 448kbps (the maximum specified for DVD) and 640kbps (the maximum specified for Dolby Digital in any format). I noted that:
my impression was that the 640kbps version was a decibel or two louder than the 448kbps version, so that would immediately invalidate any A-B comparison without a great deal of setting up
I’ve finally finished playing with receivers of limited capability, so this morning I installed a rather nice Denon AVR-4310. This has rather fuller signal information screens than the low cost receivers, so I played one of these discs again.
Yes, the 640kbps version has a Dolby Digital Dialogue Normalization (‘dialnorm‘) value of -4dB, which is a very common value for this. But the 448kbps version has a dialnorm of -5dB. Assuming that the same source mix was used for both encodes, the 448kbps will come out one decibel quieter than the 640kbps. If you see any comments around that 640kbps sounds markedly better than 448kbps based on listening tests on this disc, bear this in mind. A 1dB boost just about always makes things sound ‘better’.