<div dir="ltr"><div><br></div><div>Opus is specifically designed to survive tandeming but you need to keep the frames aligned and not mess with the gain, which your tools probably do not do.<br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Nov 16, 2017 at 10:58 PM, encrupted anonymous <span dir="ltr"><<a href="mailto:sergeinakamoto@gmail.com" target="_blank">sergeinakamoto@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>using iTunes i've noticed that AAC is</div><div>very good at re-encoding own lossy sound.</div><div>let's test Opus!</div><div><br></div><div>neroaacenc.exe -q 0.75 -if 000.wav -of 001.m4a</div><div>neroaacdec.exe -if 001.m4a -of aac001.wav</div><div>wavdiff.exe 000.wav aac001.wav</div><div>Comparing 000.wav - aac001.wav...</div><div>Max diff: -17.3867dB</div><div>RMS diff: -33.0851dB</div><div>Mean diff: -32.4582dB</div><div><br></div><div>opusenc.exe --bitrate 512 "000.wav" 001.opus</div><div>opusdec.exe 001.opus opus001.wav</div><div>wavdiff 000.wav opus001.wav</div><div>Comparing 000.wav - opus001.wav...</div><div>Max diff: -22.5646dB</div><div>RMS diff: -39.0425dB</div><div>Mean diff: -38.7372dB</div><div><br></div><div>Opus @482kbps is much better than AAC @288kbps.</div><div>now let's see what happens after 10 passes</div><div><br></div><div>Comparing 000.wav - aac010.wav...</div><div>Max diff: -16.1286dB</div><div>RMS diff: -32.3361dB</div><div>Mean diff: -31.715dB</div><div><br></div><div>AAC stepped back just a little</div><div><br></div><div>Comparing 000.wav - opus010.wav...</div><div>Max diff: -7.61385dB</div><div>RMS diff: -20.3666dB</div><div>Mean diff: -20.1286dB</div><div><br></div><div>Opus made complete disaster, but HF looks</div><div>good (so it isn't an error in frames</div><div>synchronisation of wavdiff program).</div><div><br></div><div>And no, i'm not going to do ABX test at high</div><div>bitrates because i'm not wavdiff.exe, and i'm</div><div>not going to do ABX tests at low bitrates</div><div>because i don not use them.</div><div><br></div><div>FLAC is good, but MIDI is better. Lossy codecs</div><div>"reverse-engeneering" audio back to MIDI, that's</div><div>what they do :)</div><div><br></div></div><div id="m_1631935980190637709DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br>
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