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Author Topic: Downsampling APE  (Read 1652 times)

JONCAT

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Downsampling APE
« on: March 31, 2007, 11:25:57 am »

Curious if downsampling 24/96 ape files (high compression) would or should be too much for a 64bit 3gHz cpu (single core).

I get about 80% cpu usage and choppy playback of some recent vinyl test rips at 24/96 (encoded with 4.01b) when downsampling with the MC DSP to 16/44.

DC
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morrison

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Re: Downsampling APE
« Reply #1 on: June 11, 2007, 03:07:24 pm »

I have the same problem
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Alex B

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Re: Downsampling APE
« Reply #2 on: June 11, 2007, 03:42:23 pm »

... vinyl test rips...

Why do you guys test this? Is testing these recording and playback settings interesting in some weird way?

EDIT

I just noticed that Dr started this topic over two months ago. Perhaps he does not test this anymore...   ::)
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JONCAT

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Re: Downsampling APE
« Reply #3 on: June 11, 2007, 04:18:46 pm »

I was hoping to archive recordings in 24/96. Saves times with dither and conversion.....but of course added disk space.

Unfortunately no one replied to the thread, and if my A64 3ghz rig can't handle the format then very few of my friends will be able to listen to the tracks.

What's the big surprise with us trying to use the functionality of MC and MAC? Not everyone has higher sample rate capabilities on their PCs so this is an ideal way to allow people to playback such content at 16/44.

DC
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Alex B

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Re: Downsampling APE
« Reply #4 on: June 11, 2007, 05:32:24 pm »

I don't think you can achieve any improvement by going over 24-bit/44.1 kHz or 48 kHz when recording from an analog vinyl source. You can't achieve a better s/n than 16-bit can reproduce (= 96 dB). 24-bit can be useful if the recording volume is set to a lower "safe" level and if you do some processing with an audio editor. As far as I know, 96 kHz does not provide any audible advantage.

Even many professional recording engineers are not certain if 96 KHz provides any advantage over 48 kHz when working with original digital masters. Sometimes 96 kHz is used only because the label is going to publish a DVD-Audio or SACD version of the recording and the marketing promises of "high" resolution audio must be met.

In any case, have you tried wave playback for testing the resampler's CPU usage separately? I'd guess that the most of the CPU is needed for resampling, not for decoding. MC has a high quality Shibatch resampler that uses a lot of CPU.

With lesser HW you could try 48 kHz. Conversion from 96 kHz to 48 kHz is less complex than to 44.1 kHz. This would also avoid an extra resampling step because most cheap soundcards can't handle 44.1 kHz. A 44.1 kHz signal would be resampled to 48 kHz anyway before doing the DA conversion or sending the output to SPDIF.
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Alex B

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Re: Downsampling APE
« Reply #5 on: June 11, 2007, 06:45:51 pm »

I just tested an uncompressed 24/96 wave file. My 2.8 GHz P4 couldn't play the file properly when I used the 16/44.1 DSP setting. 24/96 converted to 16/48 had no audible problems though the CPU usage was still rather high.

I wonder if the code JRiver uses allows adjusting the used resampler mode.

At least foobar's ssrc plugin have five different quality settins. The so called Ultra quality setting seems to have similar CPU usage with MC's resampler. For playback purposes at higher sample rates (over 44.1 kHz) the two lowest quality settings of foobar's ssrc resampler are generally considered to be fine.
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