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<p>Please do not take my word on this as gospel before one of us
tests it. Don't send it to Spotify yet until we know for sure. <br>
</p>
<p><br>
</p>
<p>Bob</p>
<p><br>
</p>
<p><br>
</p>
<br>
<div class="moz-cite-prefix">On 10/8/18 12:09 PM, Grimm | Eelco
wrote:<br>
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<blockquote type="cite"
cite="mid:F76AB116-FF43-4A88-B4A3-2CCA0AB01EA9@grimmaudio.com">
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<div>Hi Kevin,</div>
<div><br class="">
</div>
<div>Interesting point. The question then becomes how many fixed
point based subband decoders are still around (in percentage of
the total). Another question is whether the path from the
decoder to the volume block (that likely will perform the
normalization) is floating point. </div>
<div><br class="">
</div>
<div>All the best,</div>
<div>Eelco</div>
<div><br class="">
<blockquote type="cite" class="">
<div class="">
<div dir="ltr" class="">I'm pretty sure integer decoders are
still in use. Not on PCs or even smartphones but in
smaller audio appliances (e.g. Bluetooth speakers). In any
case, you've got to get back to integer at some point to
feed the DAC. So you either give the encoder the extra
headroom as Spotify is suggesting (see Ian's blog) or you
attenuate after the decoder as you've suggested. Maybe you
end up doing both conservatively in which case you've lost
perhaps 6 dB compared to 0 dBFS PCM which is obviously not
a small discrepancy.
<div class=""><br class="">
<div class="">
<div class="">
<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature">
<div dir="ltr" class="">Kevin Gross - AVA Networks</div>
</div>
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<br class="">
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<br class="">
<div class="gmail_quote">
<div dir="ltr" class="">On Mon, Oct 8, 2018 at 7:45 AM Bob
Katz <<a href="mailto:bobkatz@digido.com" class=""
moz-do-not-send="true">bobkatz@digido.com</a>>
wrote:<br class="">
</div>
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<div text="#000000" bgcolor="#FFFFFF" class="">
<p class="">Ian, it's been a while since I performed
this test. I would have to retest to be sure, but to
the best of my recollection, <b class="">the
clipping is ONLY on the repro side and only when
converted to fixed point.</b> Remember that all
the codecs (both encode and decode side) are 32 bit
floating point. <br class="">
</p>
<p class="">If you run an attenuator in the floating
point domain after the decoder, you can fix any over
issues which would manifest as clipping when
converted to fixed. Test it yourself. Run Apple's AU
lab with the round trip codec and Bitter placed in
critical places. <br class="">
</p>
<p class="">Then put a 24 bit dithering plugin and run
a distortion test on a sine wave to make sure it's
not an illusion. If you guys don't perform this test
before the weekend, I'll try to do it myself again.
<br class="">
</p>
<p class=""><br class="">
</p>
<p class="">Best wishes,<br class="">
</p>
<p class=""><br class="">
</p>
<p class="">Bob</p>
<br class="">
<div class="m_-238104789122760974moz-cite-prefix">On
10/7/18 7:39 PM, Ian Shepherd wrote:<br class="">
</div>
<blockquote type="cite" class="">
<pre class="">Hi All !
My recent blog post about lossy encode clipping has had quiet a bit of attention:
<a class="m_-238104789122760974moz-txt-link-freetext" href="http://productionadvice.co.uk/spotify-upload-true-peak/" target="_blank" moz-do-not-send="true">http://productionadvice.co.uk/spotify-upload-true-peak/</a>
Including an email from Robert Bleidt @ Fraunhofer. He’s asking if I have specific examples of encodes that have “baked in” the clipping, because his position is that it shouldn’t happen, these days.
I’d like to give him a helpful reply and I’ve experienced problems myself in the past with encoding from Logic and Audacity, for example, but the truth is I don’t have a collection of examples on hand to offer him.
Do any of you have recent examples that I can point him at, or know for sure of current encoders that consistently have issues with extremely loud content ?
Thanks for any suggestions,
Ian
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