Audio Memory Capacity of AP-16+

[jukingeo]

Hello All,

I just popped back into the site after a small hiatus and I see that the AP-16(+) has been released.   After reading the documentation I am already hooked and I am going to be placing an order for one soon.   I am really happy to see that the EFX-TEK genii (Jon & John) have really upped the ante and even included a STEREO amplifier on board.   I can see myself ordering several of these boards in the future as they eliminate the need to have external amplification.  So double thumbs up there ;D

Now, this might be somewhat of a rudimentary question, but since the AP-16+ relies on SD card memory, I would be correct in assuming that the total capacity of the card would be limited to the SD memory card.  That being said, what is the largest card I can put into the AP-16+?   Normally I wouldn't give it too much thought if the format used was MP3, BUT since the AP-16+ uses the much larger .wav files, capacity does come into play.

Now I read that 44.1khz is the maximum sample rate...but what is the minimum?

Thank You,

Geo

[JonnyMac]

Here's our logic with the AP-16+

1) MP3s require a decoder chip and a license fee is tagged to that -- increasing price

2) MP3 decoding can cause start-up delays that does not happen with WAV files

3) The MP3 compressor was developed when media was small (capacity) and expensive -- things have flip-flopped (cheap and massive)


The SD card firmware in the AP-16+ will work with FAT16 and FAT32 formatted cards.  FAT16 has a 2G file size limit, FAT32 has a 2T file limit (neither is likely to happen with a single WAV file).

The math.  A WAV file has a 44-byte header followed by the sample data.  For a 16-bit stereo file each sample uses four bytes.  At 44.1kHz this means that one second of audio is 176,400 bytes (0.168M*).  So... let's say you have a 1G card.  That card could theoretically hold about 6086 seconds of audio.  I say about because files use clusters.... it's too boring to get into.  

Think of it this way:  You can store about 6,086 seconds of 44.1kHz, 16-bit stereo audio per Gig*.  That's 101 minutes (1 hour, 41 minutes) per gigabyte.  Approximately.

This should put away any worries about audio storage for the AP-16+, especially as it's difficult to find cards smaller than 4G anymore.


* Note: 1M = 1024 x 1024 = 1,048,576
* Note: 1G = 1024 x 1024 x 1024 = 1,073,741,824

[JonnyMac]

Whoops, forgot to answer the last question: Technically, there is no minimum sample rate, but you may notice some aliasing (degradation of sound quality) below 22kHz.  It's minor, but noticeable (to me through decent speakers, anyway). 

Based on the math explained above, use 44.1kHz for all stand-alone files, and drop to 32K or 22.05K if you want to use the "S" (speed/pitch) feature through the serial link.

[jukingeo]

Here's our logic with the AP-16+

1) MP3s require a decoder chip and a license fee is tagged to that -- increasing price

2) MP3 decoding can cause start-up delays that does not happen with WAV files

3) The MP3 compressor was developed when media was small (capacity) and expensive -- things have flip-flopped (cheap and massive)

Understood, I ran into the same problem with licensing in regards to a virtual jukebox project I was working on with another fellow.  That is reason enough right there.   Thusfar, though, I don't have anything that uses an SD card so I don't know their capacities in context with say something like a memory stick, which is my main 'swap media' of choice.

The SD card firmware in the AP-16+ will work with FAT16 and FAT32 formatted cards.  FAT16 has a 2G file size limit, FAT32 has a 2T file limit (neither is likely to happen with a single WAV file).

The math.  A WAV file has a 44-byte header followed by the sample data.  For a 16-bit stereo file each sample uses four bytes.  At 44.1kHz this means that one second of audio is 176,400 bytes (0.168M*).  So... let's say you have a 1G card.  That card could theoretically hold about 6086 seconds of audio.  I say about because files use clusters.... it's too boring to get into.  

Think of it this way:  You can store about 6,086 seconds of 44.1kHz, 16-bit stereo audio per Gig*.  That's 101 minutes (1 hour, 41 minutes) per gigabyte.  Approximately.

NAWWWICE!  That is fantastic.  

This should put away any worries about audio storage for the AP-16+, especially as it's difficult to find cards smaller than 4G anymore.

* Note: 1M = 1024 x 1024 = 1,048,576
* Note: 1G = 1024 x 1024 x 1024 = 1,073,741,824

And those little SD cards get THAT big?   That is amazing.  Well, looks like I will be putting in an order for an AP-16+ soon.  While I loved the AP-8, this is a tremendous step forward for haunters.  Did I say I like the built in amps?

Whoops, forgot to answer the last question: Technically, there is no minimum sample rate, but you may notice some aliasing (degradation of sound quality) below 22kHz.  It's minor, but noticeable (to me through decent speakers, anyway). 

Based on the math explained above, use 44.1kHz for all stand-alone files, and drop to 32K or 22.05K if you want to use the "S" (speed/pitch) feature through the serial link.

Well for the ambiance track, that would be at 44.1, but for something like a monster roar that is being played through a small 6" extension speaker, I could drop the sample rate.  However, given the big picture you presented above, I probably wouldn't have to bother and just go with 44.1 samples throughout.

Now in terms of the speed...you have to go to 32k or 22k if you want to pitch the sample UP, correct (since 44.1k is the top limit)?  But you can pitch down without having to to 32k or 22k, correct?

Thanx again for the info.

Geo

[JonnyMac]

Yes, you can pitch down ANY sample rate.