Proposal DC Management
|Proposal pages help us get from feature requests into actual plans. This page is a proposal for automatically removing DC bias.|
Proposal pages are used on an ongoing basis by the Audacity development team and are open to edits from visitors to the wiki. They are a good way to get community feedback on a proposal.
- Note: Proposals for Google Summer of Code projects are significantly different in structure, are submitted via Google's web app and may or may not have a corresponding proposal page.
The proposal is an option (defaulted to on) to apply a low frequency high-pass filter to all audio in Audacity so that DC offset is removed.
- None so far.
- For most users of Audacity for audio processing:
- DC offset is not audible (so may not be corrected by the user) but reduces headroom for subsequent processing
- Differences in DC offset cause unwanted clicks where audio is tacked together
- It is suggested that where a waveform is inherently asymmetrical, such as in recordings of brass instruments, Audacity's DC removal method (making the average positive and negative sample values equal) may create an offset.
DC offset is an offsetting of a signal from zero. On the Audacity waveform it would mean that the waveform in default view appears not to be centred on the 0.0 horizontal line.
This page contains detailed discussion about better management of DC offset, which is asked for on Feature Requests.
The cause is almost always a fixed voltage offset before the analogue signal is converted to digital values. This voltage is known as a DC offset, and is normally so small as to not be noticeable, but with defective or poor quality hardware it may become big enough to to be a problem. This can also happen if another piece of equipment in the audio chain is defective and producing a large voltage with is being fed through to the computer.