Confusion over DV video and filters - Is it being reencoded?

[Colmino]

Welp, here's a post to peg somebody as a newbie if there ever was one. So far, I gather that DV video is not raw video, in spite of its dramatic storage requirements (some 12GB per hour), nor is it lossless. To paraphrase, it uses discrete cosine transform (DCT)-aided lossy data packing.

So far so good. Okay, on to manipulating the video with filters and whatnot, in Avisynth or VirtualDub. From what I'm reading, all that needs doing is to have the proper codec installed, and VirtualDub can manipulate the DV file directly. That much seems reasonable. But then what? If you're doing little modifications here and there, you're going to want to save your progress frequently, perhaps in stages. Would VirtualDub then save the changes as DV video?

That's where I'm stumped. If it saves it as DV video, which is lossy, we have unavoidable degradation of the video. So does it save it as raw, then? How much drive space would an hour of raw video suck up?

There's probably an easy answer to this one. Sending the video directly from VirtualDub to TMPGenc (or whatever) is not what I'm after, though.

[sacajaweeda]

If you alter it you recompress it with your choice of codec when you save it to a new file via full processing mode. If you just scene chop with VDub you can direct stream copy using the original format.

[Colmino]

If you alter it you recompress it with your choice of codec when you save it to a new file via full processing mode.

Alright. So, probably a pretty standard methodology would go something like: "Capture" DV video from camcorder using software (undetermined; not yet researched), filter / cut etc. from within Avisynth or VirtualDub, save as raw, pass raw to encoder of choice, and pass the results to DVD authoring software of choice.

That sound about right? And I'm still curious to know how much space an hour of video would take up on the drive. (Let us assume 720x480 60 fields per second with whatever's a standard high-quality stereo audio feed, or else whatever standard DV video uses.)

[sacajaweeda]

I've outlined my basic process in another thread...

https://www.videohelp.com/forum/viewtopic.php?p=814752&highlight=#814752

[vhelp]

When working with DV .avi source files ...

If you do any editing, (ie, cuting or joining) there shouldn't be any loss of
quality.

But, if you start adding Filtering, you will obviosly have loss. You have to
re-save (or re-encode) to DV format again. If you re-save an DV .avi source
file in DV format (using another DV codec) using the "Save as AVI" you'll
be re-encoding to DV, even though your source is DV. Double-edge sword
here.

But, if you select "full processing", and save as, you will not be "re-encoding"
to DV :P

Hope that made some sence.
-vhelp

[Colmino]

But, if you select "full processing", and save as, you will not be "re-encoding"
to DV.

Alright, pretty much what I thought, thanks. Which leaves my last question. How much data would that result in? Let's assume a 12GB DV file (one hour).

[vhelp]

It would still be 12g an hour.

As long as your source .AVI is an hours worth in length, when you choose
DV, it will size at ~12g.

Same goes for is you choose another codec that is specific in size, like DV is :P

Huffy will vary on content, just like others will. It will depend upon the type
of codec and its compression specifics.
-vhelp

[MrMungus]

When working with DV .avi source files ...

If you do any editing, (ie, cuting or joining) there shouldn't be any loss of
quality.

But, if you start adding Filtering, you will obviosly have loss. You have to
re-save (or re-encode) to DV format again. If you re-save an DV .avi source
file in DV format (using another DV codec) using the "Save as AVI" you'll
be re-encoding to DV, even though your source is DV. Double-edge sword
here.

But, if you select "full processing", and save as, you will not be "re-encoding"
to DV :P

Hope that made some sence.
-vhelp

You could always use a different program and export to MPEG-2...right?

[vhelp]

@ MrMungus,

Yes, you can.

You could use the codec: Matrox MPEG-2 I-frame and save to whatever
level of MPEG-2 compresion (datarate) you like (ie, Preview; Industrial;
Broadcast and Digital) But, remember.. it's I-Frame, and not your tipicle
MPEG-2 IBP frame setup. This codec is good for tradeoffs to Huffy or DV.
It's a matter of tastes and what you are doing that would require an MPEG-2
codec .AVI project :P

-vhelp

[MrMungus]

@ MrMungus,

Yes, you can.

You could use the codec: Matrox MPEG-2 I-frame and save to whatever
level of MPEG-2 compresion (datarate) you like (ie, Preview; Industrial;
Broadcast and Digital) But, remember.. it's I-Frame, and not your tipicle
MPEG-2 IBP frame setup. This codec is good for tradeoffs to Huffy or DV.
It's a matter of tastes and what you are doing that would require an MPEG-2
codec .AVI project :P

-vhelp

He couldn't export to IBP with something like Ulead?

[Colmino]

It would still be 12g an hour.

As long as your source .AVI is an hours worth in length, when you choose
DV, it will size at ~12g.

I meant if you don't choose to reencode it as DV again, but rather (eg, after filtering and other "destructive" processes) choose to save as raw. At least I think that's what you meant above when you said

But, if you select "full processing", and save as, you will not be "re-encoding" to DV.

Could be I'm again missing something critical.

[vhelp]

I may have the term incorrect :P

I mean that in order to get the standard eticits of MPEG-2, he would have to
encode the usual way (ie, TMPG or other MPEG encoder)

The item I mentioned above, is a CODEC.

I guess, you could probably re-MUX this to a standard MPEG-2, but I could
be wrong on this, and because of it being a CODEC, it could lack the tipicle
ingrediants that require a "standad" MPEG author, (assuming one is going for a
DVD project for instance)

Look at it this way. when a person is dressed for work, he/she:
* A - is wearing only underware. Still dressed, but very lean, and prob. in-appropriate.
* B - or, is wearing underware, pants, shirt, socks and shows - has all the
...ingrediants or attributes to make up a qualified person for the job.

A is the CODEC, while
B is the real-deal.

-vhelp

[bugster]

But, if you select "full processing", and save as, you will not be "re-encoding"
to DV :P

Hope that made some sence.
-vhelp

In virtualdub, when you select "full processing" you have to select a codec for it to encode to. That codec could be 'none' in which case it would save the video as uncompressed or 'raw' avi. For NTSC video at 29.97fps and 720*480 res this is about 60Gb per hour. You could select DV if you had an approriate codec installed, or any other.

When ANY application applys any sort of filter or transformation to a video, it works on the uncompressed frames to do so (in the PC's memory of course). If you want to then save this you have to either re-encode or save it as raw avi. (or frameserve the raw avi frames to another encoder). Only cuts and splices can be saved without re-encoding.

Some apps will only re-encode the portions you have changed (if you only applied transitions for instance), but many will re-encode the whole thing.

Hope this helps.

[MrMungus]

I may have the term incorrect :P

I mean that in order to get the standard eticits of MPEG-2, he would have to
encode the usual way (ie, TMPG or other MPEG encoder)

The item I mentioned above, is a CODEC.

I guess, you could probably re-MUX this to a standard MPEG-2, but I could
be wrong on this, and because of it being a CODEC, it could lack the tipicle
ingrediants that require a "standad" MPEG author, (assuming one is going for a
DVD project for instance)

Look at it this way. when a person is dressed for work, he/she:
* A - is wearing only underware. Still dressed, but very lean, and prob. in-appropriate.
* B - or, is wearing underware, pants, shirt, socks and shows - has all the
...ingrediants or attributes to make up a qualified person for the job.

A is the CODEC, while
B is the real-deal.

-vhelp

Well, I tried this as a test with Ulead MSP 6.0 and then tried to use the MPEG-2 file as a source file in TMPGEnc DVD Author and got a GOP error. That's weird. I don't think I can output to a DVD-compliant MPEG-2 in MSP6. Anyone know if you can in MSP7?