When importing movies several consistency checks are applied and a warning message may be displayed in the Import Notes column under various circumstances. The most common messages and their meanings are shown below. (These warnings are fairly technical in nature and can usually be ignored.)
|Timecode jump||This indicates that the DV timecode in the captured movie is not strictly continuous, either because the original source tape has a timecode discontinuity, because frames were dropped during capture, or possibly because data corruption occurred or the movie was edited or rendered by computer. If the ‘strictly base clips on captured DV media’ import option is on each continuous segment is processed separately during import into CatDV.|
|Dropped frame(s) between ? and ?
Repeated frame(s) between ? and ?
|These indicate shorter timecode errors of just a few frames. CatDV treats these differently and does not automatically create a new clip at each point.|
|Timecode differs (DV/QT=?)||There are two ways to determine the timecode for a particular DV frame: either based on the QuickTime ‘timecode’ track or on the digital data stored in the DV stream itself. Usually these will give the same result but if you have dropped frames or other anomalies occurred during capture the results may be different and CatDV displays a warning during import. If you have set the ‘strict’ import option then CatDV will always try to use the DV timecode and generate new clips whenever it detects a jump, otherwise it uses QuickTime’s concept of the timecode (which may agree more with what other applications use) and displays the DV timecode for reference in the DV T/C field.|
|Incorrect length (? short of ?)||This means the length of the media in the movie does not match the overall length reported by QuickTime for the movie as a whole. This can occur if frames were dropped during capture but other frames are stretched out to maintain the overall movie length. Sometimes the movie is reported as being longer than it really is and the last frame appears as one long frozen still, stretching out to give the movie its overall length. In this case the length that QuickTime thinks the movie is is shown in the message but the clip in CatDV will be shorter and reflect the media that is actually present.|
|Audio sample rate mismatch||If a DV movie has a separate audio track this message indicates that the sample rate of the audio track doesn’t agree with that originally recorded in the DV stream. This can happen if the audio was resampled during capture, or if you capture a clip where the audio sample rate changes mid way through, in which case QuickTime can sometimes get confused about the sample rate and create an unplayable audio track.Unstable frame at start|
|Skipping unstable frame(s) at ?||When the camcorder starts recording a new scene the tape may not have stabilised fully and the DV data in the first frame or two may not have a valid timecode or date/timestamp. Where possible, the unstable data is ignored and the first valid date or timecode is used instead.|
|Video and Audio differ by ? seconds||This means the audio track is shorter than the video track by the amount shown. This may indicate dropped frames or some other capture problem, but it could also mean that the movie was edited or rendered, or that the camcorder doesn’t precisely lock audio and video samples.|
|fps invalid for PAL/NTSC DV||This indicates that the frame rate is not exactly 25 or 29.97/30 fps for PAL or NTSC respectively, perhaps because the movie was rendered by computer rather than captured with a camera, or because frames were dropped during capture.|
|Average ? doesn’t match nominal ? fps||The average frame rate (total number of frames divided by movie duration) doesn’t match the typical frame rate (this could mean the movie has some dropped frames).|
Many of these messages only apply to the clip representing the movie as a whole, which is hidden by default. You should therefore show hidden clips if you are trying to diagnose capture or import problems. You can also use the Media Information dialog to display more details about a media file.
Controlling how movies are imported
Use the ‘Strictly base clips on captured DV media‘ preferences option (which is on by default) to:
- produce a log that precisely matches the DV data, even if there are dropped frames or timecode discontinuities which might mean there are gaps in the captured media;
- ignore any QuickTime timecode track and read the timecode from the DV stream instead;
- ignore the movie length as reported by QuickTime and use the length of the media itself instead (bypassing an issue affecting some capture applications where the movie may be reported as being longer than it really is).
Turn off the ‘strict’ option:
- if you are unlikely to batch recapture the material from DV tape and it’s more important to reflect the file in its currently captured state;
- for improved compatibility with other applications which are likely just to use the QuickTime information;
- if you don’t want each timecode sequence to result in a separate clip.
If you get a warning about average and nominal fps not matching and the clip appears to have wrong timecode format try toggling the “Timecode format” advanced preference option. For DV files CatDV can determine the correct format easily but for other files it can base it on the average frame rate or the nominal frame rate (time scale / nominal frame duration).
You should not normally use the “Ignore DV timecode” option but if you do then CatDV will treat DV files as ordinary QuickTime files.