Capturing via Firewire -- is the video compressed twice?

[donpedro]

Is it something like this?

Yes.

...there is DV type 1 and type2 (type1 has 1 stream for video and audio and type2 has separate streams for video and audio). Is the DV that got output from the ADVC-100 of a certain type?

It is more like different wrapper type. Each DV AVI have to be type1 or type2.

...to capture the output from the ADVC-100. When I capture I could chose what format I wanted the capture to be saved in.

It will read DV (decode) and re-encode it to new file type (codec). Re-encode = loss.

I just want to know what is the best way (least loss of any original data)

Just capture in DV AVI. It is just data copy. Capturing (encoding/conversion) is done by ADVC-100 before it hits PC.

[donpedro]

You might want to read this too

https://www.videohelp.com/forum/viewtopic.php?t=155686

[techgeek]

You might want to read this too

https://www.videohelp.com/forum/viewtopic.php?t=155686

donpedro, this topic and the one you pointed me to have really helped. I think I got it but just one more time for myself.

When the DV is sent over the firewire it is written into the avi file with no loss (as long as I dont pick one of those options to switch it to a different file format where loss would then occur). Now the avi file whether type1 or type2 has the same DV content in it; the DV (or candy as someone said) is in the wrapper but slight variation of the wrapper whether type1 or type2 (1 stream or 2 streams, maybe different avi file size but either way no loss has occured). At this point the DV/candy is the same as it was before it left the capture device via the firewire cable, ie. no loss has occured.

The DV in the avi container (the candy in the wrapper) is on the PC and ready for various possible transactions.

It is these later transactions (viewing, editing, converting to another format, etc) where the video/audio data is retrieved from the wrapper and I suppose depending on how it is retrived (which codecs used, is it converted to some other format, etc) where some loss can occur.

I feel the first two paragraphs are close to what I have been reading and I think the 3rd is where depending on what I want to do true video/audio content, loss can occur. Is this right?

[donpedro]

It is these later transactions (viewing, editing, converting to another format, etc) where the video/audio data is retrieved from the wrapper and I suppose depending on how it is retrived (which codecs used, is it converted to some other format, etc) where some loss can occur.

Hmm... not sure if you can call it loss. I would rather call it difference. Yes. There will be difference when you add (for example) text to video and save it again as DV AVI.

When you are converting there is an loss anyway. Not sure if playback/conversion is affected by codec though. I would think that only save (encoding) will make difference. But I might be wrong on this one.

As far as canfy goes.... type1 and type2 describes where is filling :P inside or on top :P (just trying to be funny)

[MrMungus]

I give up.

So what I'm gathering is that yes, you can transfer raw data to your PC but no, you probably can't display it unless it's encoded.

Wrong ! It is already encoded and compressed and you can't view it
like that. You need to DEcode it to raw bitmaps for display.

You also need to DEcode DV to raw bitmaps before you can ENcode
the raw bitmaps to another format like MPEG2

Well I learned a lot this week.

Thanks for your explanation.

[Nick Burns]

OK. I've read through this post and all subsequent links. My capture from a VHS-C through my ADVC-100 is the same data regardless if I use Scenalyzer, WinDVD, or DVIO. The codec makes no difference. Right?

At what point DOES the codec come into play? Is that only when I'm viewing it on the computer?

I've captured with DVIO, which only gives the option of TYPE 1 or 2, no codec. Isn't there a tool to show me what codec it's using?

The light is finallying dawning on me regarding this. (I hope )

[ZippyP.]

OK. I've read through this post and all subsequent links. My capture from a VHS-C through my ADVC-100 is the same data regardless if I use Scenalyzer, WinDVD, or DVIO. The codec makes no difference. Right?

Right.

At what point DOES the codec come into play? Is that only when I'm viewing it on the computer?

The ADVC-100 is a hardware converter and has a DV codec built in, the canopus one I believe (dunno for sure). If people are choosing a codec it is so that they can open the file on their PC.

[vitualis]

At what point DOES the codec come into play? Is that only when I'm viewing it on the computer?

I've captured with DVIO, which only gives the option of TYPE 1 or 2, no codec. Isn't there a tool to show me what codec it's using?

The light is finallying dawning on me regarding this. (I hope )

Transferring DV via firewire to your PC is exactly that. Transferring... copying of digital data. There is no recompression stage.

However, rather than dumping raw bits onto your HDD, most capture programs organise that digital video data into a form that is useful -- i.e., in an AVI container be it Type 1 or Type 2.

You don't need a codec to write the raw data as a Type 1 or type 2 AVI file (e.g., DVIO).

However, the raw digital video data is still compressed/encoded in the DV compression format. So if you want to UNDERSTAND (i.e., view) the data, you need a DV codec.

Here's an analogy.

If I only understand English, I can still receive (transfer) a message in Spanish via a telephone by writing down each letter at a time into a book (AVI container). However, if I want to understand what the message actually means, I still need a Spanish interpretor (codec).

You need a DV codec to be able to do anything with the transferred DV video.

Regards.

[donpedro]

...and when you edit and resave it in DV Codec or sending back to tape. You need codec for that too.

[dwiesel]

I need to discuss/question one item that I don't think was specifically raised (I hope I'm not out of the scope of this forum): the quality difference between a DV AVI file and an UNCOMPRESSED AVI file when your source is analog (i.e. from VHS). Being a newbie, please correct me if I'm wrong, but in trying to create the highest possible quality MPG (and I am a stickler), here are my steps, and results:

I have a Pinnacle AV/DV capture card along with the Studio 8 software, and also have Ulead capture software. Both capture analog to an AVI file; however, Pinnacle only captures up to DV quality, whereas Ulead will let me capture to a much larger uncompressed AVI file.

So now I had to figure out which combination of source files and rendering software yielded the best results. Ulead did poorly regardless of the source file (seems to create slight vertical lines). Pinnacle was better, but I wasn't sold. I decided to try TMPGenc and in every test it did a better job.

Regardless of what software I used to render, I found the following to always be true: going from uncompressed AVI to MPG gave a better picture than DV AVI to MPG. It seems to make sense, since capturing to DV is one compression step, and then to MPG is a second compression step. I just assume use TMPGenc to perform one compression from the uncompressed AVI to MPG. I will say that the DV AVI still looked very good, but not as good. Again, this is for those who are trying to achieve the absolute best MPG…for many, the difference may be slightly noticable, but negligable…especially when you consider how huge these uncompressed AVI files can get!

I hope this helps; I also welcome feedback from the experts to either support/dispute explain this technically. Thanks.

[dwiesel]

A correction on my last post: I discovered that the Pinnacle software I'm using DOES capture to an uncompressed AVI --I had to choose the last "custom" setting (it was either YUV or YUY1).

In comparing it to the Ulead AVI of the same source/length, it tends to be slightly smaller (yet another variable to wonder about), it has the same number of frames but the number of samples is slightly less. I'm thinking this has an insignificant affect on the final MPG, as I converted both to MPG and could see no apparent difference. Does anyone know if there is any significance to the different size AVI files? Thanks.

[duhmez]

for lossless encoding, use huffyuv . Its lossless, perfectly as good as uncompressed. And about 1/3 the filesyze.

[dwiesel]

HuffyYUV huh? Thanks, i'll try it.