Question About DV Data-Code Display

[Steve McDonald]

My Sony camcorders, both DV and Digital8, record data-code imbedded in the signal, that can be called onscreen, in two sections, with pushes of a dedicated button. This button is found on the camcorder remote controlers and also on the VCRs for these formats. The first section includes the date and time from when the recording was made and the second part has the camera settings.

When I put a Sony-recorded cassette into my JVC DV VCR, there seems no way to call up this data-code.
There is nothing in the JVC controls or manual that relates to data-code. Also, when I re-record on the JVC deck with a playback signal sent by FireWire from a Sony DV or Digital8 camcorder or VCR and then play this back into the Sony unit, only the date and time part of the data-code remains. The camera settings part is blank on the Sony display when the recording is cycled through the JVC re-recording process. This part of the data-code is also blank on the Sony display when I put such a JVC re-recorded cassette into a Sony unit and play it back there. When I re-record between two Sony DV or Digital8 units using FireWire, all the data-code is preserved.

The question is, does a JVC DV camcorder record data-code and if so, how much data does it contain?
How about other brands? Do they have variations in the type and amount of data-code they record and display? Are there differences in the amount of data-code they preserve in re-recordings of sources from units of other brands? Do other brands use different encoding for this data that is partly or fully incompatible with Sony units?

Is it just that my JVC HR-DVS3U VCR, which is a relatively low-cost model, has these limitations and other JVC models have full data-code functions?

I was under the assumption that all DV equipment was made to support the same specifications for the format.

Steve McDonald

[Rob Lohman]

This is one of the must unclear things of DV, for two reasons:

1) it is unknown whether there is a standard to what gets stored where (at least that is unknown to me)

2) it is unknown what which camera writes

The DV stream contains additional blocks with extra information
called VAUX blocks. In these blocks there are standard positions
for timecode, date and time as you found out already.

I did some tests on my XL1S and it seemed to also record certain
shooting parameters like shutter speed and gain.

I could not decode how this was stored exactly (I knew where)
and whether this was according to any standard (ie, the shutter
settings is always in these bytes and on such a scale).

From my little research I don't think such things are standard
and will work between decks and camera's (as your tests seems
to conclude as well). It might even clear sections out that it
doesn't understand (which again seems to be happening with
your testing as well).

All in all it is a very messy thing and I don't think it is as well
defined as the EXIF standard for JPEG is for example. That is
a real shame.

[Jeff Donald]

EXIF is a developing standard in and of itself. It is include in files other than JPEG, such as TIFF and various implementations of RAW. The DV standards calls for a certain data and provides an area for their writing. But no standard exists for the extra data beyond the DV spec.