Re: Low latency filtering quality

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w-u-2-o
Posts: 6024
Joined: Fri Mar 10, 2017 1:47 pm

Re: Low latency filtering quality

Post by w-u-2-o »

I'm not sure everyone agrees with us, Mark! :D

But it was a fun experiment, thanks!
K1LSB
Posts: 721
Joined: Wed Feb 05, 2020 5:25 pm

Re: Low latency filtering quality

Post by K1LSB »

Scott,

SDR Console does offer the option to record an audio file in .wav format, so here are a couple of lossless files (shorter duration but still roughly 3MB file size each). If you're feeling up to critically A-B comparing them in Audacity it I'd be interested in your findings (I don't have the familiarity with Audacity that you do).
09-Mar-2022 18h00m47s, LowLatency.wav
(2.93 MiB) Downloaded 2239 times
09-Mar-2022 17h46m15s, LinearPhase.wav
(2.98 MiB) Downloaded 2240 times
Thank you for all your efforts,

Mark
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w-u-2-o
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Joined: Fri Mar 10, 2017 1:47 pm

Re: Low latency filtering quality

Post by w-u-2-o »

Hi Mark,

Looking at the files in Audacity, zooming in (you can zoom all the way in to individual samples!) the lossless files are different. Not grossly so, but definitely different.

However, if anything they sound even more indistinguishable to me.

You should learn how to use Audacity, it's a great tool. In this case it's so very easy, and fun:

1. Install Audacity, then run it.
2. Drag and drop each wav file into the Audacity window. You'll get a stereo track for each.
3. You'll see they are not time aligned. Mouse over the title bar of the "late" track (the cursor will turn into a hand), left click and drag it to the right spot (approx.)
4. Use the zoom buttons (magnifying glasses) on the toolbar to zoom to a level where you can count individual milliseconds (0.00x resolution in the time bar). The use the horizontal scroll bar at the bottom to scroll over to some easily viewable waveform. At this point you'll also see that the waveforms are grossly the same but vary in tiny details.
5. Repeat step 3 above to get them within 1ms, it's easy to do so.
6. Hit the play button. You'll be hearing both tracks.
7. Start hitting the solo buttons in turn, this will ping pong you back and forth between the two tracks.

73,

Scott
K1LSB
Posts: 721
Joined: Wed Feb 05, 2020 5:25 pm

Re: Low latency filtering quality

Post by K1LSB »

Thanks Scott, you make everything sound so easy!

Mark
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