DSF oversampling. D64 vs. D128. Real advantage of sound?
Educational line
Many times people ask me about necessity of oversampling DSF (1-bit HD audio files) from D64 to D128. This is a complex issue. Many links in viewed chain. But we try to watch possible advantages of D64 to D128 conversion. At least theoretically for almost ideal conditions.
How compared D64 and D128
1. As source file took WAV-file (sample rate 176 kHz) contains sweep sine 0 ... 20 kHz.
2. Source WAV was converted to files DSF D64 (further DSF-D64) and DSF D128 (further DSF-D128) via AuI ConverteR 48x44.
3. File DSF-D64 was converted to file DSF D128 (further DSF-D64-D128) via AuI ConverteR 48x44.
4. Files DSF-D64, DSF-D128 and DSF-D64-D128 was converted to WAV files for comparing in spectrum analizer.
Attention: All pictures showed below depend on algoritms of spectrum analizer (FFT length, applied window, overlap, ...), encoding and decoding PCM to DSF and DSF to PCM.
For experiments you can download AuI ConverteR 48x44 FREE
WAV, FLAC, AIFF, ALAC, (1-bit audio) ISO, DFF, DSF, WMA, mp3, CD-audio...
WARNING: DSF, DFF is supported in maximal PROduce-RD and configurable Modula-R
FREE demo mute 2 second silence in the output middle of ISO tracks, DSF, DFF
with length more 3 minutes
Comparing
Here showed cuts by level of sonogramm (frequency-time spectrogramm). Vertical axis is frequency, horizontal axis is time.
Level -4 dB. Peak of sweep sine signal lower this level.
Original PCM DSF-D64 DSF-D64-D128 DSF-D128
Level -5 dB. Here we watch sweep sine signal (green arrow point it out). Its frequency grow with time.
Original PCM DSF-D64 DSF-D64-D128 DSF-D128
Level -132 dB. Here we watch noise (red arrow point it out) at DSF-D64. Other files while haven't noise.
Original PCM DSF-D64 DSF-D64-D128 DSF-D128
Level -137 dB. First noise peaks appear at DSF-D64-D128. DSF-D128 has pure sweep sine as before.
Original PCM DSF-D64 DSF-D64-D128 DSF-D128
Level -140 dB. DSF-D128 has pure sweep sine as before.
Original PCM DSF-D64 DSF-D64-D128 DSF-D128
Level -164 dB. DSF-D128 has first noise peaks. DSF-D64-D128 almost hidden under noise. DSF-D64 hidden.
Original PCM DSF-D64 DSF-D64-D128 DSF-D128
Rapidly
Noise floor of DSF-D64 begin at -132 dB, DSF-D64-D128 at -137 dB, DSF-D128 at -164 dB.
Resume
1. Noise floor of DSF-D128 better DSF-D64 converted to D128 at 27 dB.
2. Noise floor of DSF-D128 better DSF-D64 at 32 dB.
3. Noise floor of DSF-D64 converted to D128 better original DSF-D64 at 5 dB.
Thus
If we convert PCM to DSF, using of D128 give us gain of useful loudness range 32 dB.
If we convert DSF-D64 to DSF-D128 we have gain of useful loudness range 5 dB.
These values depend on audio conversion software and hardware used for playback and methods of measurement.
For DSF we get improvement of noise level when converting D64 to D128
Update: experiment was executed with old version of AuI ConverteR. Modified D64 modulator work better and currently not difference between D64 and D64, upsampled to D128.
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