compression question

[clearwind]

Is the video compression done by DV itself or by the software you used to capture (dump) the video?
I always thought that the source that saved in the DV tapes is the original AVI file without any compression.
But after I've read the post "sticky" on the first page, I doubt my thought.

I've captured the video from tapes with DV avi codec and get some good pictures, though I can still see some noise (caused by low bitrate) on the edge of objects. Then I re-captured the same source with uncompressed avi codec which produce some hell large video.
And when I view it, I "thought"it's better.

However, my question means that if the video is compressed by the DV device. Then what I've done (capture by uncompressed AVI) is meaningless.

Also, how much the storage a DV tape is (14GB)?


Lot of thanks. :)

[bb]

Originally posted by clearwind
Is the video compression done by DV itself or by the software you used to capture (dump) the video?
The compression is done by hardware in the camcorder, so the video on tape is already DV compressed. The "capture" process via firewire should be called "streaming", as it's nothing but copying the DV data from the camcorder to the PC's hdd through a serial device.

Originally posted by clearwind
I always thought that the source that saved in the DV tapes is the original AVI file without any compression.
Wrong assumption :)

Originally posted by clearwind
But after I've read the post "sticky" on the first page, I doubt my thought.
... with good reason.

Originally posted by clearwind
I've captured the video from tapes with DV avi codec and get some good pictures, though I can still see some noise (caused by low bitrate) on the edge of objects. Then I re-captured the same source with uncompressed avi codec which produce some hell large video.
And when I view it, I "thought"it's better.
How did you "re-capture" the video? Following the analogue path?

Originally posted by clearwind
However, my question means that if the video is compressed by the DV device. Then what I've done (capture by uncompressed AVI) is meaningless.
Exactly. Sorry.

Originally posted by clearwind
Also, how much the storage a DV tape is (14GB)?
Depends on the length. If you count the video only, there's a factor of 1.5 between SP and LP, too. DV is stored at a rate of ~3.5 MB/sec, so you can easily calculate the tape size in GB.

bb

[trevlac]

Here is a link with a nice short what is dv faq. It has the size calculated out for you ... ;)

http://graphics.csail.mit.edu/~tbuehler/video/dv.html

Here is a rather technical discussion of DV vs MJPEG. Depending on how you did your 'capture' test, this might be of interest.

http://www.adamwilt.com/DVvsMJPEG.html

[clearwind]

wow
thanks bb and trevlac

big helps there :cool:

[bb]

You're welcome. :)

bb

[theReal]

I've captured the video from tapes with DV avi codec and get some good pictures, though I can still see some noise (caused by low bitrate) on the edge of objects. Then I re-captured the same source with uncompressed avi codec which produce some hell large video.

You probably watched the DV file with the standard DV filter playback settings (which are half resolution and therefore bad). As soon as you configure the playback filter to play DV at full resolution there should be no difference to the uncompressed avi (that has been DV compressed before).

Uncompressed HD recording and editing is only needed for HD sources like 35mm film scans that you want to record back to 35mm film and show in a movie theater ;)