SD card Latency test tool

[zachtos]

Is there any testing tool out there that can determine latency for multi-file playback?

There are lots of tools that test sustained speed (class 4-10), but we only care if it is able to play multiple files well on Teensy. Kingston for example, is terrible at playing multiple sounds, and sandisk is OK. But, sandisk stopped selling 4 and 8gb cards that worked well, and now their 16gB cards are slower and have some distortion. I really need a way to test a batch of cards to know what is going on quantitatively.

 

[UhClem]

I suspect that this depends more on the software (which you don't describe) than on the SD card.

Any FAT library is going to create occasional pauses when it needs to search for a new cluster. If it does that poorly, then it could cause trouble. But you have to buffer enough data so that a delay in any one read isn't a problem.

I don't know if multi-block reads speed reads up as much as it does writes but it couldn't hurt. So allocate a bunch of data buffers at least 4K in size. Nice even multiples of 512 please and as many as you have memory for. It is also a good idea to make sure that an integer number of them fit in a cluster. Then have a process that reads in data whenever an empty buffer is available.