[linux-audio-dev] int32 to int24 conversion speeds not bad ! (for ardour for example)

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Subject: [linux-audio-dev] int32 to int24 conversion speeds not bad ! (for ardour for example)
From: Benno Senoner (sbenno_AT_gardena.net)
Date: Thu Jun 08 2000 - 13:23:36 EEST


Hi,
I just made a little experiment:

Sometime ago there was the discussion about reading/saving the
audio data in 32bit or 24bit when using for example a harddisk recorder like
ardour in conjunction with the Hammerfall.
Notice 24bit samples on disk means 25% less data compared to the 32bit samples.
And not only you save space but you can run a higher number of tracks
simultaneously , since you cut the bandwidth by 25% too.

I made a little test program which simulates all the needed
24bit<-->32bit conversions on a Hammerfall with all 52 channels active.
(26 input and 26 output)

results:
on my PII400 it takes about 9.5secs to process 10240000 (10million)
frames (notice 1 frame = 1 sample x 52 channels).

That means about 1078000 frames / sec

At our 48000Khz rate , we get a mean CPU usage of about:
48000 / 1078000 = 0.0445 = 4.45%

And of course with the faster CPUs this value drops to 1-2% which is negligible.

I think that everyone of us producing 24bit HDR apps should include this
32bit<-->24bit conversion option, because it will allow a higher number
of simultaneous tracks and especially people with not-so-fast disks
will benefit from this.

I attached my benchmark code.

comments ?

Benno.



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