Free CFVT Practice Questions

Question 1

At a burglary scene, an examiner has authority to acquire a recorder's footage. The relevant interval will begin overwriting in about 30 minutes. The recorder is operating normally, and a native export with its player can finish in six minutes. A lower-resolution MP4 export is also available. Powering down would end the only authenticated session; the administrator cannot presently restore access. Which acquisition should take priority?

Accepted Answer

Begin the native export and retain the associated player and metadata.

Answer

Shut down the recorder and remove its drives for write-blocked imaging before attempting an export.

Answer

Make the lower-resolution MP4 export first to avoid a proprietary player.

Answer

Record the monitor output first to capture the displayed timestamps.

Question 2

In progressive video from a fixed CMOS camera, vertical bars on a sliding gate appear upright when the gate is stationary but lean when it moves rapidly across the same part of the image. Shortening the exposure makes the bar edges sharper without removing the lean. What mechanism best accounts for this combination of findings?

Accepted Answer

The sensor records the moving gate row by row at different times.

Answer

Radial lens distortion displaces the moving bars near the image boundary.

Answer

Motion blur integrates each bar over the duration of its exposure.

Answer

An incorrect pixel aspect ratio stretches the gate during playback.

Question 3

A vehicle's front tire crosses two surveyed ground lines 9.00 m apart along its path in source frames 101 and 111. Their presentation timestamps are 90,000 and 144,000 ticks, with a time base of 1/90,000 second per tick. Examination has established that these timestamps represent the elapsed capture time between the crossings. The file also reports an average rate of 25 frames/s, but its frame intervals vary. What average speed is supported, rounded to the nearest km/h?

Accepted Answer

54 km/h

Answer

15 km/h

Answer

81 km/h

Answer

74 km/h

Question 4

A verification log reads "SHA-256 match" when a forensic disk image reaches the laboratory. During acquisition, however, the tool recorded 128 unreadable sectors and substituted zeros at those locations. The comparison digest was calculated from the completed image, not the source disk. What does the successful verification establish?

Accepted Answer

The delivered image matches the acquisition output, including the tool's substituted bytes.

Answer

The matching digests verify that every source sector was acquired without alteration.

Answer

The matching digests establish that the unreadable source sectors originally contained zeros.

Answer

Analysis must be deferred until every previously unreadable sector has been recovered.

Question 5

A twelve-frame average makes a moving delivery van's registration plate less readable: characters acquire doubled edges, although each source frame contains only one plate. The frames were aligned to the stationary background. The selected images have comparable plate size, viewing angle, and illumination. What should change before averaging is repeated?

Accepted Answer

Register the plate itself across the source frames before averaging.

Answer

Sharpen the current average to separate the doubled character strokes.

Answer

Average additional background-aligned frames to improve noise suppression.

Answer

Use a temporal median while retaining the current background alignment.

Question 6

An examiner corrects lens distortion and uses surveyed floor points to establish a validated image-to-floor homography for a lobby camera. Two people's shoe-floor contact points are clearly visible. Their heads and one raised hand are also visible, but no vertical scene calibration has been performed. Which quantity can be measured using this floor transformation alone?

Accepted Answer

The floor-plane distance between the two visible shoe contact points.

Answer

Each person's height from the shoe-floor contact point to the top of the head.

Answer

How high the raised hand is above the floor directly underneath it.

Answer

The distance from the raised hand to the other person's head.

Question 7

A proposed "lossless intermediate" uses this sequence: decode 10-bit 4:4:4 video, convert the frames to 8-bit 4:2:0, then encode with lossless FFV1. The requirement is to retain the original decoded sample values. Where must the workflow change?

Accepted Answer

Feed the lossless encoder the original 10-bit 4:4:4 samples without the downconversion.

Answer

Replace FFV1 with uncompressed video after retaining the 8-bit 4:2:0 conversion step.

Answer

Upsample the converted 8-bit 4:2:0 frames back to 10-bit 4:4:4 before encoding them.

Answer

Change the output container from Matroska to AVI while retaining the existing sample conversion.

Question 8

Surveillance footage and photographs of a seized car agree in general body shape and paint color. However, sufficiently detailed views establish a fuel-filler door on the left rear quarter of the recorded car and only on the right rear quarter of the seized car. Road signs establish that the footage is not mirrored, and contemporaneous photographs rule out a later change to the seized car's body configuration. How much weight should the structural difference receive?

Accepted Answer

The reliable structural mismatch supports exclusion of the seized car.

Answer

The two agreeing class features outweigh the single conflicting structural feature.

Answer

A conclusion requires a fixed minimum number of matching or conflicting features.

Answer

The comparison must remain inconclusive unless the recorded registration plate can be read.

Question 9

Emergency personnel have isolated the electrical supply at a flooded business. A disconnected mains-powered video recorder is recovered with water still inside its enclosure and its hard drives visibly wet. An officer wants to reconnect it briefly because the native export function may offer the easiest access to the footage. What is the appropriate immediate response?

Accepted Answer

Keep it unpowered and arrange recovery by personnel equipped for liquid-damaged media.

Answer

Dry the outside of the enclosure, then attempt a short, supervised native export.

Answer

Remove the drives and immediately try write-blocked imaging before corrosion can progress.

Answer

Use a replacement power supply to test the recorder without relying on its wet supply.

Question 10

Moving moov ahead of mdat in a non-fragmented MP4 shifts the media chunks to new byte positions. The encoded samples, their order, and their intended timing remain unchanged. To make this reorganization playable, which entries require updating?

Accepted Answer

The absolute chunk offsets stored in stco or co64.

Answer

The decoding-time sample deltas stored in stts.

Answer

The encoded sample sizes stored in stsz.

Answer

The presentation-versus-decoding offsets stored in ctts.

Free CFVT Practice Questions

Domain 1: Acquisition of video files from various recording devices

Question 1

Domain 2: File verification and integrity

Question 2

Domain 5: Video file format conversion

Question 3

Domain 6: Video processing techniques

Question 4

Domain 9: Video enhancement/clarification

Question 5

Domain 11: Identification of damaged media

Question 6

Domain 13: Photogrammetry

Question 7

Domain 14: Comparative analysis

Question 8

Domain 19: Identification of video/image attributes and compression artifacts

Question 9

Domain 22: File format and metadata analysis

Question 10

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