dv and huffy theroy

[gavo]

If you captured through 1394 to huffy loseless and then made mjpeg to edit, would you get better quaitly as dv is lossy and what do there mean when there say dv is 4:4:1 in luma?

[trevlac]

If you 'captured' DV via firewire and re-compressed it to Huffyuv, you would probably not loose anything (but time). {Note: You would have to convert from the DV color to huffyuv color, and depending on how you did it there could be differences in your final result ... but I doubt you could see them}

If you then re-compress your huffyuv to mjpeg (which is generally lossy) you would loose more time and probably some data (depending upon how much you compress).

So in the end ... it is best to stick with what you have and not keep recompressing it.

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4:1:1 referres to NTSC luma being sampled at the full rate, and color being sampled at 1/4 the rate horizontally, and the full rate vertically.

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PS: I could be off the mark on my answer, because you could be talking about an SDI connection feeding 4:2:2 uncompressed data. I think an AJA (MAC) device does this thru a 1394 connection. But you probably don't have one of those. ;)

[gavo]

ok thanx so basialy dv camreas and dv codec are so simliar it best not to use any loseless codec?

[bb]

Originally posted by gavo
ok thanx so basialy dv camreas and dv codec are so simliar it best not to use any loseless codec?
DV camcorders have a (hardware) DV codec integrated, so you have the DV format already on the tape. When you "capture" the video to your PC, it's in fact a streaming (copy) process, which does not alter the video at all (neither does it alter the audio, of course).

DV is told to be stable across several generations, so there's no reason to switch to an uncompressed format (e.g. Huffyuv). If you modify and render your file many times, then you might be better off with Huffyuv.

There's no reason to use MJPEG in the video editing process, despite you need MJPEG for some special reason. It's just another format conversion which can decrease quality.

bb

[ADLANCAS]

Originally posted by bb
When you "capture" the video to your PC, it's in fact a streaming (copy) process, which does not alter the video at all (neither does it alter the audio, of course).
Is it possible to filter the video during streaming process ? Maybe with ffdshow ?
If yes,
Duration of copy process is increased ?
Do you know some applications that makes this process possible ?

Thanks,

Alexandre

[bb]

Originally posted by ADLANCAS
Is it possible to filter the video during streaming process ? Maybe with ffdshow ?
The DV capture programs I have used so far do not support filtering while streaming. There are programs to capture directly to MPEG-2, which may involve some MPEG-2 specific filtering, e.g. using MainConcept MPEG Encoder. But what you are looking for is not available as far as I know.

Originally posted by ADLANCAS
If yes,
Duration of copy process is increased ?
Do you know some applications that makes this process possible ?
The duration of the copy process is predefined by the tape speed, so you can't capture at speeds other than realtime. At least I don't know any camcorder that supports something like "double speed dubbing / capturing".

To sum it up, for DV sources you capture first, then edit, filter, and encode.

bb

[ADLANCAS]

thanks.

Alexandre

[Mug Funky]

i've heard that some DV decks can do varispeed, but i haven't been able to confirm this. it'd double your chances of dropping frames though (and my hard disks are barely up to it already)

[communist]

Faster than real-time dubs ? Only with SDI AFAIK.

[hanfrunz]

Faster than real-time dubs ? Only with SDI AFAIK.
Sorry thats wrong. SDI is always realtime. But there is an interface called SDTI (on BetacamSX-decks for example) and if you have an editing system supporting this you can import material in more than realtime. There also is an IMX-Deck calld e-VTR from Sony, which supports access via Ethernet (FTP) i think this can be faster than realtime too. I never heard of something like this for DV...

hanfrunz