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------------------------------------------------------------------------
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(edi-18) Intelligent system for setting the internal sample rate.
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- submitted: smassy, 17.10.2001
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- done: kaiv, 31.01.2002
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- added: edi-18 implemented; engine samplerate is now
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set automatically - if object sample rates don't
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match, an error is printed
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- added: ecasoundrc - 'default-audio-format'; same syntax
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as with the -f option; defaults to s16_le,2,44100,i
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- removed: ecasoundrc - 'default-samplerate'
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- removed: -sr option; not needed anymore
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- S.Massy, 17.10.2001:
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- When all objects have the same sr, use it as internal sr also.
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- When objects have different sr always set internal sr equal to the highest
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sr connected in the cs.
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if (-i:48000 && -o:48000) { sr = 48000 }
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if (-i:44100 && -o:22050 && -o:48000) { sr = 48000 }
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That would improve ecasound's ease of use for many as well as its
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apparent sound quality to a new user; because right now as soon as the
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internal sr and the objects' sr differ, sound quality drops
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dramatically because of the way ecasound converts sr's (as we
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discussed on the list a while ago.)
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Also maybe something similar should be done for rt objects. Because
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if you have something like `-i:test.wav -o:alsa" though test.wav is at
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a sample rate of 11025, alsa device is still open at 44100; ideally,
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-f and -sr should only be used to override (or for headerless
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------------------------------------------------------------------------
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- should be placed to ECA_CHAINSETUP::enable() (after input
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- ECA_ENGINE takes caref of initializing chains, so it's
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- issue a warning if -sr was not given and resampling results
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------------------------------------------------------------------------
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What if we just removed implicit resampling altogether? My reasoning
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- current resampling is not high-quality (mostly just causes
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- for any kind of realtime work, resampling should _not_
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be used (wastes cpu-resource for no good reason)
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- only real use for resampling is file format conversions
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- by removing the "resampling_needed()" check we
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make the common code path a little bit faster (although
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- we avoid problems with unexpected resampling
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As a result you could not execute a chainsetup, where sampling rate of
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one or more objects differs from engine's sampling rate.
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If this was done, implementation of 'edi-18' would be reduced to:
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- find the common sampling rate between audio objects
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- if found: set engine's rate to it
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- else: print an error message
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This would also make the -sr option obsolete.
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For cases where resampling is needed, a new audio object type could be
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added - something like:
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ecasound -f:16,2,44100 -i resample,22050hz_file.wav,44100 -o output.wav
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As a bonus, as now resampling would be a special-case operation, we are
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not limited to light resampling algorithms. In practise we could use a
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much more high-quality (=cpu-heavy) alternative (if someone has the time
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Documentation/archived/edi-18.txt
