- It would be nice to think that you could just go and buy any computer, - install a bit of software on it and start using it to record and create - music. This idea isn't wrong, but there some important details that it - misses. -
-- Any computer that you can buy today (since somewhere around the end of - 2012) is capable of recording and processing a lot of audio data. It - will come with a builtin audio interface that can accept inputs from - microphones or electrical instruments. It will have a disk with a huge + It is nice to think that one could just go and buy any computer, install a + bit of software on it and start using it to record and create music. This + idea isn't necessarily wrong, but there are some important details that it + misses. Any computer that can be bought today (since somewhere around + the end of 2012) is capable of recording and processing a lot of audio data. + It will come with a builtin audio interface that can accept inputs from + microphones and/or electrical instruments; it will have a disk with a huge amount of space for storing audio files.
+
- When you are recording, editing and mixing music, you generally want to
- work with very little latency between the time that
- a sound is generated and when you can hear it. When the audio signal
- flows through a computer, that means that the computer has to be able to
- receive the signal, process it and send it back out again as fast as
- possible.
- And that is where it becomes very important what computer system
- you have, because it is absolutely not the case that any
- computer can do this job well.
+ However, when recording, editing and mixing music, it is generally desirable
+ to have very little latency between the time a sound is generated
+ and when it can be heard. When the audio signal flows through a computer,
+ that means that the computer has to be able to receive the signal, process it
+ and send it back out again as quickly as possible. And this is where it
+ becomes very important what computer system is being used for this
+ task, because it is absolutely not the case that
+ any computer can do it well.
- Routing audio through a computer will always cause some delay, but if it - is small, you will generally never notice it. There are also ways to work - in which the delay does not matter at all (for example, not sending the - output from the computer to speakers). + Routing audio through a computer will always cause some delay, but if it is + small, it will generally never be noticed. There are also ways to work in + which the delay does not matter at all (for example, not sending the output + from the computer to speakers).
+- The latency that you want for working with digital audio is typically in - the 1–5 ms range. For comparison, if you are sitting 1 m - (3 ft) from your speakers, the time the sound takes to reach your + The latency that is typically needed for working with digital audio is in the + 1–5 ms range. For comparison, if one is sitting 1 m + (3 ft) from a set of speakers, the time the sound takes to reach the ears is about 3 ms. Any modern computer can limit the delay to - 100 ms. Most can keep it under 50 ms. Many will be able to get - down to 10 ms without too much effort. If you try to reduce the delay - on a computer that cannot meet your goal, you will get clicks and - glitches in the audio, which is clearly extremely undesirable. + 100 ms; most can keep it under 50 ms. Many will be able to get down + to 10 ms without too much effort. Attempting to reduce the latency on a + computer that cannot physically do it will cause clicks and glitches in the + audio, which is clearly undesirable.
| Video interface | +Poorly engineered video interfaces (and/or their device drivers) can
"steal" computer resources for a long time, preventing the audio interface
- from keeping up with the flow of data
- |
|---|---|
| Wireless interface | +Poorly engineered wireless networking interfaces (and/or their device + drivers) can also block the audio interface from keeping up with the flow of + data. |
| USB ports | +When using an audio interface connected via USB, and sometimes even if + not, the precise configuration of the system's USB ports can make a big + difference. There are many cases where plugging the interface into one port + will work, but using different USB port results in much worse performance. + This has been seen even on Apple systems. |
| Internal USB Hubs | +Ideally, all USB ports should connect directly to the main bus inside the + computer. Some laptops (and possibly some desktop systems) come wired with an + internal USB hub between the ports and the system bus, which can then cause + problems for various kinds of external USB devices, including some models of + audio interfaces. It is very difficult to discover whether this is true or + not, without simply trying it out. |
| CPU speed control | +Handling audio with low latency requires that the processor keeps running + at its highest speed at all times. Many portable systems try to regulate + processor speed in order to save power—for low latency audio, this + should be totally disabled, either in the BIOS or at the OS level. |
| Excessive Interrupt Sharing | +If the audio interface is forced by the computer to share an interrupt + line (basically a way to tell the CPU that something needs its attention) + with too many other (or wrong) devices, this can also prevent the audio + interface from keeping up with the flow of data. In laptops it is generally + impossible to do anything about this. In many desktop systems, it is possible + at the BIOS level to reassign interrupts to work around the problem. |
| SMIs | +SMIs are interrupts sent by the motherboard to tell the computer about + the state of various hardware. They cannot safely be disabled, and they can + take a relatively long time to process. It is better to have a motherboard + which never sends SMIs at all—this is also a requirement for realtime + stock trading systems, which have similar issues with latency. |
| Hyperthreading | +This technology is becoming less common as actual multi-core CPUs become + the norm, but it still exists and is generally not good for realtime + performance. Sometimes this can be disabled in the BIOS, sometimes it cannot. + A processor that uses hyperthreading will be less stable in very low latency + situations than one without. |
| Excessive vibration | +This doesn't affect the flow of data to or from the audio interface, but + it can cause the flow of data to and from (spinning) disk storage to become + much slower. If a computer going to be used in an environment with + loud live sound (specifically, high bass volume), make sure it is placed so + that the disk is not subjected to noticeable vibration. The vibrations will + physically displace the read-write heads of disk, and the resulting errors + will force a retry of the reading from the disk. Retrying over and over + massively reduces the rate at which data can be read from the disk. Avoid + this.If you find this hard to believe, check + out this + video which shows the effects of merely shouting at your drives. This + is likely not an issue with contemporary SSD drives, which have no + spinning/head mechanisms. |
+ Richard Ames presents a long (28 + minute) video + that is very helpful if you want to understand these issues in more + depth. It is a little bit Windows-centric, but the explanations apply to + all types of computers and operating systems. +