Published by PitchChanger · Updated · How these guides are made
How to use this workflow
Read the selection in frames
Open Audio Trimmer, load a short file and set both fades to 0 while checking timing. Note the displayed selection frame count.
Convert each boundary separately
Multiply milliseconds by sample rate and divide by 1,000, then round each boundary. Subtract the rounded start from the rounded end.
Preview and save the result
Choose Preview result, then Download WAV. Check the saved frame count and listen at both cut points before using the clip.
A frame contains one sample from every channel
At 44,100 Hz, one frame spans about 0.022676 ms. At 48,000 Hz it spans about 0.020833 ms. Stereo adds a second sample at the same time position; it does not halve that interval. Audio sample frames are different from video frames.
The browser decode step can resample a file to its AudioContext rate. Use the decoded rate for this calculation, rather than assuming that a 44.1 kHz source always stays at that rate inside a waveform tool.
Reproduce a 1.001–2.003 ms selection
The table is an original calculation verified by calling the current trimSelection engine on one-second silent buffers at each stated rate. Fades were disabled. Silence isolates frame-count behavior; it does not test whether a musical cut sounds natural. The engine copies frames from start up to, but excluding, end.
Swipe or scroll sideways to read all columns.
| Decoded rate | Start frame | End frame | Saved frames | Saved duration |
|---|---|---|---|---|
| 44,100 Hz | 44 | 88 | 44 | 0.997732 ms |
| 48,000 Hz | 48 | 96 | 48 | 1.000000 ms |
Why subtracting times first can give the wrong count
At 44.1 kHz, the requested boundaries map to 44.1441 and 88.3323 frames, which round to 44 and 88. The actual start is 0.997732 ms and the exclusive end is 1.995465 ms. The requested time difference is 1.002 ms, but the copied interval contains 44 frames.
Always round the boundaries before subtraction. If two very close entries round to the same frame, there is no valid nonempty selection. Increase the end or move the start; adding more displayed decimals cannot create half a frame.
Frame accuracy does not guarantee a clean word ending
After checking timing, listen for a clipped consonant, breath or discontinuity. Move the boundary to preserve the sound you need. A short fade changes the copied samples but does not recover a word ending that was excluded. There is no automatic zero-crossing snap or silence detection in this trimmer.
This workflow saves one contiguous WAV interval. Use the cutter for several retained pieces, or the converter after trimming if a recipient needs MP3. Keep the original and record the rate and frame indices when an exact handoff matters.
Common questions
Does 0.001 ms field spacing mean microsecond audio precision?
No. The field can describe a finer time than the sample grid. At 48 kHz, boundaries still resolve to whole frames about 0.020833 ms apart.
Does an end frame of 88 include frame 88?
No. The retained interval ends before frame 88. Starting at frame 44 and ending at 88 copies 44 frames.