What's block size?

[357mag]

Next to sample rate in Preferences there is something called block size. What should that be set at if you are recording at 48000?

[Gibson_GM]

Layman's answer: 64, 128 or 256, as your machine is capable of using without glitching out. The lower the number, the less latency you'll experience while recording.

1024 on playback to lower the burden on the CPU while processing (mixing, adding FX/vsts etc).

[King Stupid]

It's the buffer. The lower it is, the lower the latency.
Also, the higher chance of glitches and buffer underruns.

[serr]

Originally Posted by 357mag

Next to sample rate in Preferences there is something called block size. What should that be set at if you are recording at 48000?

It's very literally the latency control. The lag from input to output.

If you are playing live through the computer and thus monitoring live inputs along with processed sound through the computer, you need to not have any perceivable lag. The block size is the latency control for that.

The caveat is there will be a limit to how low you can set it and still have stable dropout free audio! Too laggy of an interface (it's baseline inherent latency) and/or too slow of a computer means you can't really do live sound. If you can't set low enough for no lag without losing stability, well that's a show stopper.

That's the long and short there.

For post work (ie mixing) where you no longer monitor any live performance in real time, set the block size to a high setting like 512 or 1024 samples. (Always multiples of 32 samples.) Leave your CPU for mix processing.

And now you know why some people monitor live inputs with the low latency digital mixers built into audio interfaces! Bypass the DAW and leave the block size set high for stability.

PS. 48k sample rate does in fact lead to the lowest latency possible with the lowest CPU hit. Going to 96k cuts the latency in half but typically uses more than 2x CPU, for example. 44.1k doesn't really lower the CPU use for the increased latency at that rate.

[Tadamori]

for recording at 48kHz, a block size of 128 or 256 samples is usually ideal, balancing low latency with stable performance.

[Coachz]

Block Size in Reaper: A Quick Explanation

Block size in Reaper refers to the amount of audio data processed by your computer's audio interface at a time. It's a crucial setting that affects latency (delay) and CPU load.

How it works:
Smaller block size: Lower latency (less delay between playing and hearing), but higher CPU load.
Larger block size: Higher latency, but lower CPU load.
Where to find it:
You can adjust the block size in Reaper's preferences:

Go to Preferences > Audio > Device.
Look for the Request block size option.
When to use what:
Low latency: For recording instruments or playing with minimal delay (e.g., guitar, vocals), use a smaller block size (like 64 or 128).

High CPU load: If you're using many plugins or processing heavy audio, a larger block size (like 512 or 1024) can help prevent audio dropouts.

Remember: The optimal block size depends on your computer's specs, audio interface, and the complexity of your project. It's often a matter of finding the best balance between low latency and stable performance.

[souk21]

Don't know if this was mentioned but some hardware don't respect the "Request block size" setting in REAPER and have a separated software to choose the block size.