raw dv

[matriplex]

I want to ask some questions about capturing dv.
my question is: when we record anything on tape how does camera keep the video?
does camera compress the video when recording to tape with dv encoder?
or we compress the video when we capture the video with any software's dv encoder?
and do we have any chance to have raw dv when capturing?
if we have the chance; what are the advantages and disadvantages in quality and disk space?
with which programs can I capture raw video?

[jagabo]

The camcorder compresses the video before putting it on tape as compressed digital DV. When you capture, more of a transfer really, with the computer you are simply taking DV from the tape and putting it in an AVI file.

[redwudz]

The camera compresses the video from the image sensors to DV and records that on the tape. DV has about a 5:1 compression ratio. When you transfer it to the computer from the camera, that's just a file transfer, there is no capturing and you can't change the DV stream. You can modify it in the computer, but that's encoding.

You can't 'capture' raw video from the camera because there isn't any accessible. DV uses about 13GB per hour of hard drive space. There are higher end video cameras that use formats other than consumer DV and do have higher quality, but at a much higher price.

I suppose my question is: Are you having a problem with the quality of your DV? What's on your DV tape should be exactly what is transfered to your computer. If the quality seems to be lower, then it may be a viewing problem with the computer.

[matriplex]

thanks for reply but wyh is there a format(raw dv)?
if we transfer dv file as dv file no one doesn't need a raw dv format?
where is raw dv format used?

[edDV]

I want to ask some questions about capturing dv.
my question is: when we record anything on tape how does camera keep the video?
does camera compress the video when recording to tape with dv encoder?
or we compress the video when we capture the video with any software's dv encoder?
and do we have any chance to have raw dv when capturing?
if we have the chance; what are the advantages and disadvantages in quality and disk space?
with which programs can I capture raw video?

A typical DV format camcorder (Digital8, MiniDV, DVCAM, DVCPro) processes the camera section data from RGB into YUV (8 bit 4:1:1 sampling) and then encodes to DV format which applies 5x intraframe compression to make a 25Mb/s DV video stream. Intraframe compression occurs within a frame similar to JPeg. DV maintains all frames (as I frames) for easy editing.

The 25 Mb/s DV video stream is combined with PCM audio to make the DV format stream that is recorded to tape as data, or passed to the IEEE-1394 (firewire) link as a live DV stream. This could be considered "raw" DV.

When the tape is played back, the same "raw" stream data that was recorded is sent to the IEEE-1394 link as a "raw" DV format stream. At the computer end this stream can be processed in several ways but is usually just collected into an AVI file wrapper as DV-AVI . The resulting file is about 13.5 GB per hour and contains the same "first generation" DV data that was created in the camcorder's hardware DV encoder. There is no loss from recording to tape and/or streaming the DV data over IEEE-1394. So, "raw DV" is created in the camcorder's DV encoder and that same data is collected into the DV-AVI file with no loss.

Alternatively the IEEE-1394 DV stream could be routed to a transcoder and compressed in a different way to say MPeg2 or MPeg4 or decompressed to raw YUV. Decompression will not increase picture quality, it will just increase the stream datarate and file size.

With me so far?

PS: If you are talking about the "raw" *.DV format that is used on MAC, that is just a different file format structure. The data saved is the same as with DV-AVI.

The overall quality of the DV stream depends on the quality of the source. DV Format camcorders range from $250 consumer models up to $45,000 (plus) professional models. Most of the differences are in the camera section. The recorded DV format stream is the same for all.

[Cornucopia]

To add to that good explanation:

In addition to your camcorder doing the realtime compression while recording, it may do it for analog input pass through as well. Good feature to have if you've got a library of analog tapes.

Also, the DV-codec in your computer can encode or re-encode to DV (if you're rendering some processed/composited material), but for straight transfer & simple edits, it doesn't need to do that, just pass through the originally (camera)encoded frames.

Are you also asking if one can bypass the camera's compression and get a straight uncompressed RGB or YUV feed?
Most cameras will not allow you to do this, but a few will (read: $$$$). If they can, they'll be sending this out of the SDI outputs (if they've got it) or Composite/Component Analog outputs (whichever they've got).

Scott

[matriplex]

thanks for all replies.
As a result I can understand that the camcorder compresses the video as dv when recording on tape and we only transfer the file.
only a few cameras don't compress the video when recording on tape when we transfer that videos they are called as raw dv.
am I wrong?
please make clear sentences. I don't know English very vey well

[edDV]

thanks for all replies.
As a result I can understand that the camcorder compresses the video as dv when recording on tape and we only transfer the file.

A DV camcoder compresses to a raw DV stream. The raw DV steam is recorded to tape as stream data (usually not a file).

only a few cameras don't compress the video when recording on tape when we transfer that videos they are called as raw dv.
am I wrong?

This is not right. The DV encoder in the camcorder creates a raw DV stream that can be sent to tape or to the IEEE-1394 port as a live stream. Almost all DV format camcorders record raw stream data to tape. There is no file or operating system in the camcorder. Raw data is saved to tape. Raw data is played from tape to the IEEE-1394 port. There is no file until the data is collected at the computer.


PS: High end camcorders like the Sony XDCAM or Panasonic AG-HVX200 do have operating systems in the camcorder and are capable of creating a DV file in the camcorder. The XDCAM saves this file to a BluRay DVD. The AG-HVX200 saves the file to a PII flash card. In both cases, the camcorder can be accessed as an external disk drive for file transfer. This is not the case with normal DV camcorders.

There are other high end camcorders that can output an uncompressed live stream from the camera as SMPTE-259M serial data (aka "SDI"). In all cases any local camcorder recording to tape will be compressed (e.g. DV, Digital Betacam, HDCAM compression formats).

[matriplex]

I know I tired you but as a result can I say these?

1-Dv camcorder records the video(it is raw dv)
2-and then dv camcorder encodes (compresses) the video (it is only ''dv'')
3-after compressing dv camcorder puts the compressed video in to tape.
4-at the end we only transfer video from tape to computer as a file

if you help me I will be very happy.

[jagabo]

I know I tired you but as a result can I say these?

1-Dv camcorder records the video(it is raw dv)
2-and then dv camcorder encodes (compresses) the video (it is only ''dv'')
3-after compressing dv camcorder puts the compressed video in to tape.
4-at the end we only transfer video from tape to computer as a file

if you help me I will be very happy.

1) First the camera reads digital data from its CCD. Exactly what form that data takes varies depending on the CCD design. Let's just say at this point we have uncompressed digital image data.

2) The camera then compresses that data with a DV codec. It now has "raw DV".

3) It writes that data onto tape. It is still raw DV. This step is skipped when using a camera in pass-through mode.

4) It then sends that raw DV over the firewire cable to the computer. It is still raw DV.

5) The computer reads the raw DV from the cable, adds a little strutural and descriptive information, and puts it into a file. You now have a DV AVI file.

[edDV]

and if you read the DV video and audio from that file, it is identical to the data that was created in the camcorder's DV encoder. It is still first generation. That is the main advantage of digital recording.

[LucasNyX]

OK, I'm really impressed with that explanation.
So to finish it:
How can we import the files with THE BEST settings possible (about the RGB or the YUV told earlier).

About that I'm always having the aspect ratio (distortion) with problems... even when I put in Adobe Premiere PRO CS3 the DV NTSC settings (with the 720x480 (1,2 pixel)) marked.
Thanks very much.

[edDV]

Import files from what?

DV video, like DVD MPeg2 has non-square pixels. If you set a DV project (4:3 or Wide) in Premiere, aspect ratio should be handled automatically.

Explain your problem in more detail.

[jagabo]

I think Premiere handles everything in RGB so you may be screwed there.

[edDV]

Depends what he is doing and the I/O hardware used. Premiere Pro can work in YUV mode with hardware drivers.

[LucasNyX]

I said import , but i wanted to say only capture! Transport the video from the Camcorder(tape) to the PC by firewire.
But...
How can I use RGB or YUV (or any kind of settings about them...) in Premiere PRO?
And wich one of these are the best, and why?

About the Aspect Ratio distortion I think it's the aspect ratio of the pixels that is distorting the video. I recorded in True 16:9 in a Panasonic PV-GS500 and the problem persists even when I put DV widescreen project in Premiere PRO CS3...
Thanks!

[edDV]

Normally aspect ratio is set in the DV camcorder settings as 4:3 or wide (16:9). In both cases the DV format is 720x576* @ 25 Mb/s. The aspect setting applies a flag identifier to the stream data for 4:3 (default) or wide.

When you capture the stream to a file at the computer, usually the aspect ratio flag is set appropriately in the file header. Some older programs assume 4:3 regardless resulting in aspect ratio errors unless one manually edits the file properties.

Premiere Pro normally processes in RGB for filters and effects. This is hidden to the user who sees a DV project with ability to export in a variety of formats. Simple cut edits result in frame copies from the source file to the export file so no loss results.

Optionally Premiere Pro can work with YCbCr (real time) hardware. These cards support certain transitions and filters in hardware. Usually these cards work with simultaneous uncompressed source and record to a video server.


*720x480 in Brazil

[LucasNyX]

I've bought it in USA!
Isn't it NTSC?
720x480?????

P.S. - It realy sounds strange...

[edDV]

I've bought it in USA!
Isn't it NTSC?
720x480?????

P.S. - It realy sounds strange...

The original poster is from Turkey which would be 720x576. USA and Brazil use 720x480.

[LucasNyX]

Okay, Thanks by the way.
The last think to improove the knowledge;

Always capture it to another Hard Disk which doesn't have the OS installed.

Thank you all, Thanks edDV!

[jagabo]

Always capture it to another Hard Disk which doesn't have the OS installed.

That was true back in the days of slow drives and raw YUY2 captures. With DV capture it doesn't matter any more.