Sidebar 2: Example: Portland State Chamber Choir: Amazing Grace: Noisefloor Analysis
This graph examines the run-out noise (at around 5:24) for the original WAV file recorded by John Atkinson, MQA (with and without decoding) and the underlying MQA channel noise in this recording (also with and without decoding). Also shown are reference levels for 16, 18 and 20-bit TPDF dither in a channel sampled at 88.2kHz (footnote 1).
In the graphs the noise-floor curves overlay for both MQA decoded and Original master.
We can also see that the shaped HF noise introduced by the MQA encoder and 'heard' without a decoder is removed by the decoder.
Note: The noise seen by a Legacy (no-decoder) listener is the sparse signalling channel, not lossy noise in the file.
Without Decoder (at 44.1kHz): MQA channel noise is lowest around 4kHz @ 17.5 bits with a channel capacity of 15.8 bits which has been shaped.
With Decoder: MQA channel noise is lowest around 5kHz @ 20.1 bits with a channel capacity of around 19 bits in an 88.2kHz channel, which has been shaped to exploit the content (footnote 2).
Footnote 1: The analysis uses 21.53Hz bins (=44100/2048 and 351800/16384) giving an offset of +13.33dB wrt 1Hz. Footnote 2: Of course not all DACs can reach this low level of in-band noise.
This graph examines the run-out noise (at around 5:24) for the original WAV file recorded by John Atkinson, MQA (with and without decoding) and the underlying MQA channel noise in this recording (also with and without decoding). Also shown are reference levels for 16, 18 and 20-bit TPDF dither in a channel sampled at 88.2kHz (footnote 1).
In the graphs the noise-floor curves overlay for both MQA decoded and Original master.
We can also see that the shaped HF noise introduced by the MQA encoder and 'heard' without a decoder is removed by the decoder.
Note: The noise seen by a Legacy (no-decoder) listener is the sparse signalling channel, not lossy noise in the file.
Footnote 1: The analysis uses 21.53Hz bins (=44100/2048 and 351800/16384) giving an offset of +13.33dB wrt 1Hz. Footnote 2: Of course not all DACs can reach this low level of in-band noise.
