- the Delay Before a Transfer of Data Begins Following an Instruction for Its Transfer, also Known as “Delay”
- in Digital Audio Processing there are Several Components of Latency
- Latency is Only Problematic when Recording a Band (No Problem for Mixing / Mastering Except that After Pressing Play it Takes Time to Hear Something when Latency Heavy FX Processors are Used)
- the Most Important is the “Round Trip Latency” which is the Delay from Initially Sending Audio into a Computers Audio Interface Input, to the Moment the Same Audio is Available at the Computers Audio Interface Output
- you can Never Record and Listen at the Same Time with Zero Latency for Several Reasons
- Mostly Because of the Sample Buffer in the Computer which is the Buffer, thus Finite Time the Computer Needs to Process Data which is Measured in Samples (Minimum 14 Samples in 2017 but More Often 32 or 64 for Most Interfaces)
- while 128 to 256 is a Good Compromise to Handle Latency and CPU Load as Audio Must Keep Flowing at the Sample Rate Being Used
- to Empty a Buffer of 32 Samples at 44.1kHz a Computer Needs Around 0.73ms (or 0.00073 Seconds)
- Since Round Trip Latency Needs Buffering at the Input and Output Stage you Need to Double the Time, i.e. for 32 Samples 2 x 0.73ms = 1.5ms
- In Addition, an Analog Audio from a Mic or Amp Must Go into the Interface and be Converted to a Digital Data Stream Using an A to D Converter (A/D) and that Conversion Adds More Delay
- and After Zipping through the DAW, to Listen to Audio the Interface Must Convert the Data Stream Back to Analog Using the D/A Converter which Adds Even More Delay
- so A/D Needs About 1ms and D/A Needs About 1ms, thus the Initial 32 Samples 1.5ms Delay Receive at Least Another 2ms and can Increase from 3ms to 6ms (that is Sound Travelling 1-2 Meter through Air)
- these Delays are Affected by the A/D and D/A Hardware and the Drivers Used by the Audio Interfaces
- DAW Itself Does Not Add any Delay Beyond the Buffer Latency
- but DAW FX Processors such as Linear Phase EQ, Lookahead Featured FX, Convolution can Add Thousands of Samples (from 2048 to 8192)
- e.g. 2048 Samples at 44.1kHz Result in Over 46ms of Delay (which is Nearly a Slap Back Delay)
- During Mixing / Mastering the DAW Automatically Compensates for Any Delay with a PDC (Plugin Delay Compensation), i.e. Aligns All Tracks Equal to the Plugin Delay
- while During Recording it is Simply the Best to Not Use Plugins that Add a Delay Beyond the Buffer Latency
- while a Singer / Musician can Live with a 5ms Delay, a Drummer Might be Concerned Even with a 4ms Delay
- Thunderbolt Interfaces can Provide a Low True Round Trip Latency of Under 2ms
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