Preserving miniDV quality in exported movie

[chiragmp]

I have a Sony miniDV camcorder. I imported the contents to MacBook Pro using iMovie '11. The tape was split and captured as several "clip###.dv" files. The extension is ".dv".

Now I want to merge these several clip###.dv into one big file - tape1.dv, without losing accuracy/resolution. So I dragged all the clips into iMovie's project area. I don't want to add any transitions, titles, etc. I just want to merge the clips into a single file - that's all. So after dragging and dropping all the clips into the project area, I selected "Share -> Export Using QuickTime -> Movie to DV stream". In this popup window under Options, I have these selections:

DV Format = DV
Video Format = NTSC
Scan Mode = Interlaced
Aspect Ratio = 4:3
(checked) Preserve Aspect Ratio Using = Letterbox
Audio Format Rate = 48.000KHz

The merged tape1.dv (iMovie adds the .dv extension) is not the same quality as the individual clip###.dv!! tape1.dv is decidedly grainier than the individual clip###.dv. What am I doing wrong here? Are there any options that I can use to preserve the original quality of the source material? File size is not a concern.

Thanks for your help.

[aedipuss]

were the originals widescreen 16/9 or 4:3? the checkbox in "preserve aspect ratio using = letterbox" is weird. dvavi isn't ever letterboxed unless used in a 16/9 movie inside a 4:3 resolution for dvd. that would cause the entire video to be re-encoded.

[chiragmp]

Hi aedipuss,

The original source material is 4:3. I am basing it on the fact that I have another tape that when captured in iMovie creates more "rectangular" clips than this particular miniDV tape that creates more "square" clips. Is there a good way to confirm this in the imported clip - like querying the clip property?

The "preserve aspect ratio using = letterbox" was my selection. Would that be the cause of video degradation? By default, it was unchecked. Should I uncheck it when creating the merged tape1.dv? I am not interested in creating a DVD, yet. I just want to collect 50 clips into one meaningfully named file without loss of quality.

Thanks.

[aedipuss]

dvavi can be either 4:3 or 16/9, but nothing else. there is no square version. properties should show 720x480 4:3 or 720x480 16/9.

i would try unchecking the letterbox option.

[JohnnyMalaria]

If the .dv files are true .dv files then you can simply concatenate them via the command line. .dv files contain only the data for the DV stream itself - there are no wrappers etc (such as Quicktime .mov or .avi etc). I vaguely recall reading that some .dv files created by Mac apps are not true .dv but have some padding. Anyway, I'm not at all familiar with Unix but the Windows command line equivalent would be:

copy /b part1.dv+part2.dv+part3.dv tape.dv

to join three .dv clips together. The /b tells the OS to treat the files as binary and not text.

This preserves everything and affects nothing whatsoever. It definitely works on the Windows platform and I have used it with .dv files generated on a Mac.

I'm sure someone can translate for the Mac.

John.