What is Redaction in Video, Audio, and PDF

What is Redaction in Video, Audio, and PDF

Redaction is the deliberate omission or concealment in a multimedia recording of information. Redaction involves removing sensitive information from data such as documents, audio files and videos. Redaction in its application may include but is not limited to, video recorded by body-worn cameras, 911 phone calls, digital video recorder systems, in-car video systems, jail or prison phone services, crime scene videos, crime scene photos, and video evidence collected during investigations.

As with paper documents, before releasing outside the organization, it is normal for organizations to redact confidential information, material of a graphic nature, or information that is restricted by privacy provisions. Typically, it requires editing a digital text by censoring, but not necessarily omitting, specific words, phrases or whole paragraphs. The sections to be redacted are essentially blacked out to prevent them from being read. This is often done in government or court documents where these sections are blacked on individual copies that need to go to organizations or people that do not have the right authorization or privilege to know of certain pieces of information. If redaction is applied to electronic documents, however, it simply means the permanent removal of information and not the obscuring of it.

Reasons for Redaction

For varied reasons, law enforcement and organizations release multimedia. These include, but are not limited to:

  • Enhanced transparency;
  • Freedom of information act or other requests for open records;
  • Public disclosure for safety alert or suspect identification assistance;
  • For research use;
  • Use in criminal or civil litigations;
  • Court order or a Judge’s ruling.

Before release, an organization may be required to redact information contained within a recording. Redaction is most often necessary to preserve individuals’ privacy or to comply with regulations and laws governing the protection of information that is personally identifiable. These include, but are not limited to:

  • Health records covered by the Act of Health Insurance Portability and Accountability (HIPAA);
  • Regulations on criminal justice, covered by the Criminal Justice Information Services (CJIS);
  • A victim, suspect, prosecutor or bystander’s identity;
  • Techniques and methods of investigation;
  • Sensitive metadata such as GPS coordinates, serial numbers or personal identifiers.

Before sending the content to the practitioner, decisions must be made on what information is to be redacted.

What is Video Redaction

Redaction may be used in the process of making unclassified portions of a secret recording available to the public or may be used to protect people’s privacy. An example of the redaction of video involves blurring the faces of people captured by surveillance cameras. This is necessary when the system is being tested or maintained by a person who lacks the required authorization to view faces, for example.

Forms of Video Redaction

When deciding on the most appropriate form of redaction, you have to carefully consider the desired outcome, based upon the type of information you’ve been requested (if applicable) and any existing legal or organizational requirements. Two forms of redaction are discussed below.

  • Global: In video redactions, filters like mosaic, blur or a solid shape, are applied to entire segments of the video recording. This method of redaction can be done with open-source software and scripted to perform bulk editing, but provides little control over the edits applied. Global redaction may not be necessary to comply with specific requests for information, as all text will be similarly obscured; however, it is undoubtedly ideal for preparing a recording that is released to the press or the public on a voluntary basis. The preferred approach for audio redaction is to substitute the whole audio signal with a tone within a section and the corresponding channel.
  • Selective: This redaction is for videos only and requires the user to monitor specific content and track object(s) across frames that are sequential so as to apply the filter(s) selectively. With professional, purpose-built, and competent video redaction software, this method of redaction can easily be done.

Video Redaction Filters

There are several filters available for the redaction of video segments. The type, effect, and strength of the filter added to the recording will ultimately be determined by the video recording, video circumstances, justification for redaction, and organizational procedures.

Examples of commonly used filters in video redaction include mosaic, blur, and solid form (e.g., color-filled rectangle, oval, or circle). It is highly advisable to select a filter that is irreversible once rendered and exported from the video redaction software.

  • Solid Shape: This filter can be defined by any shape and color; however, the shape’s opacity must not permit visibility of the edited material.
  • Blur: Blurring aims to reduce image clarity by using a mathematical algorithm to change pixel values. This process, when applied to selected areas of the video, makes them unidentifiable. When using this redaction, all filtered content must be sufficiently covered by the degree of blurring.
  • Mosaic (Pixilation): This filter distorts the selected region by horizontally and vertically copying pixels into adjacent pixels. Ensure that the cell size or pixel matrix size makes all redacted content unidentifiable when using the mosaic filter.

Combining of multiple filters can also be used to ensure complete redaction of identifiable objects.

What is Audio Redaction

An audio recording transcript is a written record of what has been said during the interview. It could be a transcript of an interview with a witness, a conversation by telephone like a 911 call, or videos from a video camera worn by a person.

Although getting a transcript of an audio from a recording is helpful, understanding what was being said is often necessary.

If the audio recording itself is released to another entity, then any sensitive information in that recording must also be deleted. This is referred to as audio redaction. The sensitive information is usually replaced by a controlled signal or silence.

Audio redaction should be based on a transcript provided by the requestor and marked with a clear indication of what content should be redacted. The findings should be checked for consistency upon completion of the redaction. Redacted audio should be substituted with a coherent and distinct regulated signal, but not distracting from the surrounding audio. The signal’s consistency indicates clearly to the listener that redaction has taken place.

If it is necessary to redact audio from a video recording, care must be taken to keep the audio and video streams synchronous.

  • Tone(Bleep, Beep): The recommended audio redaction signal is a single tone or set of sounds. The sounds should be distinctive but not distracting from other content. Once established, this signal should be used for all redaction activities to create a consistent expectation for the listener.
  • Silence: Silence is generally not a recommended method of redaction, as a redacted segment can be confused with original content that contains silence. Silence should only be used when multiple simultaneous audio channels require independent redaction and an inserted tone risks masking content on another channel.

What is PDF Redaction

Now that new documents are being generated on computers, filled out on computers, and exchanged via computers; it makes sense that computer programming options are the only way to redact sensitive information on PDFs. In PDF, redaction applies to the editing of text either by omission of certain details for publication. Recorded interviews are usually transcribed. Redaction removes portions of text or images from a PDF file indefinitely and replaces them with black rectangles. The remainder of the document is not compromised and can usually be viewed and printed.

PDF redaction involves two main steps – select areas for redaction, and then apply redactions:

  • Select words, paragraphs, pages or images, and apply redaction-marks. Text and image redaction marks are not destructive. They show which sections are selected for redaction in the PDF document.
  • When you are satisfied that all your redaction marks are suitably placed, and you want to remove content marked for redaction permanently, then you apply redactions.

OCR and Automated Redaction

There have been major technological advances in the 21st century which offer an automated option to the redaction process. Many companies have vast amounts of non-searchable, image-based PDFs, typically coming from design packages as scans faxes or outputs. Instead of using a dark marker on documents, many Recorders now use OCR to analyze scanned images of paper documents. OCR technology transforms scanned images into a digital format that allows search engines based on rules to identify sensitive information in the text. To recognize potentially confidential information, the search engine uses a combination of words, phrases, text patterns, proximity, and location. For example, in a document, the engine can find the keyword “SSN” followed by a pattern of numbers like xxx-xx-xxxx. Combining the keyword with the text format gives high confidence that the potentially sensitive information needs to be redacted.


Technology is required in order to redact information from recordings. Video redaction software allows importing, updating, modifying and exporting of your recordings. Choosing video redaction software with adequate features is essential to perform redaction work within the framework of the practitioner’s organizational procedures and capabilities. The program should at least be able to decode different types of video and audio codecs, allowing recording to be trimmed and provide options for video and audio filters (e.g. blur, solid form, tone). We also recommended that the program be able to track objects automatically for the adjustment of shape, size and location. Before use, emphasis should be placed on software testing and validation to ensure that once rendered, the results are irreversible.