Is DV AVI Loss-Less Compression?

[rkr1958]

I've been backing up my 1-hour DV tapes but capturing them to my hard driver and then recording them back out through my camera to a backup tape. Here's are my questions:
(1) Is the AVI video captured from these tapes compressed?
(2) If so, is this compression loss-less?
(3) Assuming no computer glitches in writing to the backup tapes, should I expect any degradation in the quality of the video on the backup tapes versus the quality on the original tapes?

[mbellot]

As long as you are doing all of your transfers via Firewire (IEEE1394) and *not* editing the footage then the copy should be identical to the original.

DV is not lossless, but what you are doing (if you are doing it like I described) adds no further loss because you are not recompressing the DV file, only sendig it back out to the camera. The "loss" was already in the original file.

If you edit the AVI, your editing package will recompress some/all of the AVI resulting in a small loss of quality (depends on the codec used). Intelligent editors (like Premiere) only recompress "around" edits and leave the bulk of the AVI untouched.

[JHebert]

The DV format is compressed when you first record the tape on the camcorder. The compression is NOT lossless, although this is a common misconception. The DV compression ratio is around 5:1 with a bitrate of about 25Mb/s (or 3.6MB/s). However its a very high quality format so don't let that bother you.
However, when you copy a DV tape by transferring from Cam<>PC via Firewire that process does not cause any additional loss because it is basically just a digital copy process. If you edit the video on the PC before sending it back to the Camcorder I guess the recompression of the edited portions might cause some loss but I think it would be relatively minor.

[rkr1958]

Thanks for the replies ... let me be more specific and see if I understand. Since I'm running W98SE I have do the capture in four segments due to the FAT32 4-GB file size limitation. I'm capturing through firewire card and using Pinnacle Studio DV. I then add a "title" in front of the four captured AVI-segments. The only rendering required is for this title. I then record back out to my DV camera and a new tape. What I've heard you two say is that the AVI segments on the backup tape will have the same quality as the AVI on the original tape. Is this correct?

[JHebert]

I don't know about Pinnacle Studio DV specifically, but most good editing programs will only re-render any edits you make to the video, and any additional stuff like titles or transitions, but leave the rest of the original video intact without re-rendering it. It sounds to me that since you are only adding a title segment at the beginning, the rest of the video should be left intact and not suffer any quality loss when you copy back to tape.

[rkr1958]

Thanks ... Appreicate your help.