Definitions
Irregularity: An event of interest to preservation (Audio Recording Preservation Use Case).
Irregularity Image: An Image corresponding to an Irregularity (Audio Recording Preservation Use Case). It is represented as a JPEG file corresponding to that Irregularity.
Irregularity File: A JSON file containing information about Irregularities of the ARP inputs (Audio Recording Preservation Use Case).
Syntax
https://schemas.mpai.community/CAE/V2.1/data/IrregularityFile.json
Semantics
| Name | Definition |
| Offset | Integer value indicating the time offset (in milliseconds) between Preservation Audio File and Preservation Audio-Visual File. The time reference is the Preservation Audio File. |
| Irregularities | Array of Irregularities. Each Irregularity shall have at least an IrregularityID, TimeLabel and TimeReference. |
| IrregularityID | UUID [7] that identifies an Irregularity. |
| Source | “a”: if the Irregularity is detected by the Audio Analyser. “v”: if the Irregularity is detected by the Video Analyser. “b”: if the Irregularity is detected by both Audio Analyser and Video Analyser. |
| TimeLabel | Time Label indicating the timing of an Irregularity. The time reference is the Preservation Audio File. |
| AudioFileURI | URI of the Audio File related to an Irregularity. It is only used in the message between Audio Analyser and Tape Irregularity Classifier. |
| IrregularityType | Class of an Irregularity (see values in following Tables). |
| IrregularityProperties | Optional object containing additional specifications about the current Irregularity. |
| ReadingSpeedStandard | Speed standard applied during the digitisation phase. It can be one of the following values: 0.9375, 1.875, 3.75, 7.5, 15, 30. These values are in inch per seconds (ips). This field is optional. |
| ReadingEqualisationStandard | Equalisation standard applied during the digitisation phase. It can be one of the following values: “IEC”, “IEC1”, “IEC2”. The notation refers to documents [14,15]. The association with ReadingSpeedStandard shall be compliant to the values indicated in [14,15]. This field is optional. |
| WritingSpeedStandard | Speed standard applied during the recording phase. It can be one of the following values: 0.9375, 1.875, 3.75, 7.5, 15, 30. These values are in inch per seconds (ips). This field is optional. |
| WritingEqualisationStandard | Equalisation standard applied during the recording phase. It can be one of the following values: “IEC”, “IEC1”, “IEC2”. The notation refers to documents [14,15]. The association with WritingSpeedStandard shall be compliant to the values indicated in [14,15]. This field is optional. |
| ImageURI | URI of the Image related to an Irregularity. It is only used in the messages between Audio Analyser, Tape Irregularity Classifier, and Packager. |
Table 27 – Extended list of Irregularities that can be detected by the Video Analyser
| Code | Name | Definition |
| sp | Splice | Splice of magnetic tape to magnetic tape, or leader tape to magnetic tape (or vice versa). |
| b | Brands on tape | Most of the brands consist of the full name of the tape manufacturer, logo, or tape model codes. The brand changes in size, shape, and colour, depending on the tape used. |
| sot | Start of tape | It refers to what happens when the tape playback starts, at which point it is neither under tension nor in contact with the capstan and pinch roller. The distinguishing visual characteristic of this class is the tape coming in tension and in contact with the capstan and pinch roller. This happens at the beginning of the Preservation Audio-Visual File. |
| eot | Ends of tape | It refers to what happens when the tape reaches its end of playback, at which point it is neither under tension nor in contact with the capstan and pinch roller. The distinguishing visual characteristic of this class is the tape coming free or completely detached from the capstan. This happens at the end of the Preservation Audio-Visual File. |
| da | Damaged tape | It groups all kinds of damages on the surface of the tape and alterations of the tape shape. This class includes: |
| di | Dirt | Tape contamination and dirt: presence of mould, powder, crystals, other biological contaminations, or similar sullying. |
| m | Marks | Marks, signs or words written on the back of the tape (i.e., the nonmagnetic side) or on the adhesive tape of splices. |
| s | Shadows | The class contains frames in which shadows or reflections are temporarily cast on the tape by external objects in motion. |
| wf | Wow and flutter | Pitch variation due to the recording or playback equipment. If this effect is due to recording equipment it is detectable only on the Preservation Audio File and not on the Preservation Audio-Visual File. |
Table 28 – List of Irregularities that can be detected only on the Preservation Audio File
| Code | Name | Definition |
| pps | Play, pause and stop | Sound audio effects derived by play, pause or stop buttons during the recording. In a single tape several recordings from different sources can be recorded. This kind of irregularities cannot be identified in the digital video. |
| ssv | Speed standard variation | Instant when the recording has a variation of the speed (and, in case, of the equalization) standard. |
| esv | Equalization standard variation | Instant when the recording has a variation of the equalization standard without a change of the speed. |
| sb | Signal backward | Instant when a recording start playback audio signal backwards. This could happen in case of incorrect signal recording or digitization. |
The Irregularities that could be identified in both audio and video are: sp, sot, eot, da, di, and wf.
Considering that Brands on tape are usually very frequent and repetitive, only one occurrence (usually the first one) is considered as a valid Irregularity by the Tape Irregularity Classifier.
Shadows has no impact on the signal. They should be considered because they can have an important impact on the classification, but they should not be included in the Preservation Master File.
