Supported Parameters

The DV format specifies how to encode a variety of useful parameters within the DV data stream. These include, but are not limited to, the date and time of the recording, the timecode, the video stream format, the audio stream format and camera information. The Enosoft Enhanced DV Decoder supports decoding of all of these parameters. Other parameters may also be encoded within the DV data stream, however these are generally proprietary in nature and, at this time, are not supported. The decoder also supports an additional parameter that indicates the color space being used for the decoding of the video portion of the DV data stream.

The decoded parameters are incorporated into the decoded video frame in the form of overlaid text. The text format has the following fixed parameters:

• Fixed spacing, face and character size
• Fixed color (maximum legal white)

The background of the text overlay can be assigned one of three options: opaque (black), semi-transparent or transparent:

The position and appearance of each text overlay item can be controlled using the configuration utility.

Record Date

The date on which the source DV stream was recorded, if present, is extracted and represented by a string of characters with one of three formats:

• YY/MM/DD. e.g., 05/03/01 represents 1^st March, 2005.
• MM/DD/YY. e.g., 03/01/05 represents 1^st March, 2005.
• DD/MM/YY. e.g., 01/03/05 represents 1^st March, 2005.

The default format used by the decoder depends upon the short date format defined in the host computer's Regional and Language Options (see Control Panel).

It is possible that the audio and video streams have different record dates (e.g., following audio dubbing). Should this be the case, the date of the video stream recording is used.

Record Time

The time at which the source DV stream was recorded, if present, is extracted and represented by a string of characters with the general format HH:MM:SS. e.g., 23:56:00 represents 11:56pm.

It is possible that the audio and video streams have different record times (e.g., following audio dubbing). Should this be the case, the time of the video stream recording is used.

Note   The DV format specification is very clear about how to indicate whether or not a given parameter is present in the data stream. Some implementations of the DV format do not adhere to the specification, indicating the presence of valid parameter information even when such information is not present. The Enosoft Enhanced DV Decoder behaves as follows:

If the DV data stream indicates that valid parameter information is NOT present, the decoder returns an empty (or blank) result.

If the DV data stream indicates that valid parameter information is present but the corresponding decoded information is not meaningful, the decoder returns results such as "--/--/--" or "--:--:--;--".

Time Code

The timecode for the current video frame, if present, is extracted and represented by a string of characters with the general format HH:MM:SS:FF (non-drop frame) or HH:MM:SS;FF (drop frame). The selection of non-drop frame vs. drop frame depends upon the video system (PAL or NTSC, respectively).

Video Information

The decoder can display information about the format of the video stream being decoded. Specifically, the video system (i.e., PAL or NTSC) and the aspect ratio (i.e., 4:3 or 16:9) can be displayed.

Audio Information

The decoder can display information about the format of the audio stream being decoded. The display includes the audio sampling frequency (32kHz 16-bit Single Stereo Channel, 32kHz 12-bit Dual Stereo Channel, 44.1kHz 16-bit Single Stereo Channel, 48kHz 16-bit Single Stereo Channel). If the audio stream is "locked" (e.g., 32kHz 16-bit or 48kHz 16-bit DVCAM), the display includes a padlock symbol.

Camera Information

The DV specification permits information relating to the camera settings in effect at the time of the recording to be stored within the DV data recorded on tape. The majority of camcorders support recording a subset of settings, including the ones listed below. The Enosoft Enhanced DV Decoder displays this information in the following manner:

Hint: You can click on an item in the above image to get more information or scroll down to the item of interest.

Image Stabilizer

If the camera's image stabilizer was on at the time of the recording, the display will show . If the stabilizer was off (or no information has been recorded), the display will show .

Auto Exposure Mode

The following auto exposure modes are supported by the DV standard:

• Full automatic
• Gain priority mode
• Shutter priority mode
• Iris priority mode
• Manual

The decoder will display "AUTO", "GAIN", "SHUTTER", "IRIS" or "MANUAL". If no information is present, the display will show "-".

Shutter Speed

The DV specification allows the electronic shutter speed to be recorded. By definition, the speed is an exact multiple of the scan line rate. For NTSC, the scan line rate is 29.97 x 525 = 15734.25 lines per second; for PAL, it is 25 x 625 = 15625 lines per second.

However, Enosoft has identified that the shutter speed indicated by some camcorders (and video recorders that can decode the embedded information on tape) is not the same as that according to the DV specification.

For example, the Sony DSR-PDX10 supports twenty shutter speeds, ranging from 1/4s to 1/10000s. The camcorder can display the shutter speed on its built-in display. The values displayed by the camcorder do not fully agree with the values according to the DV specification. The Sony DSR-11 video cassette recorder displays the same information as the camcorder. The calculated vs. displayed values are shown below:

Careful analysis of the video signals with an oscilloscope suggest that the displayed values are a closer approximation of the real shutter speed rather than the value that the camcorder records to tape. Since different manufacturers of DV equipment may implement the encoding of shutter speed information in different ways, the values that the Enosoft Enhanced DV Decoder displays can be customized. See Mapping Shutter Speed Values in the Registry.

White Balance

If a white balance setting has been recorded, the decoder will display "WBx" where x is a decimal number between 0 and 6, inclusive. The DV standard defines these as:

0. Candle
1. Incandescent lamp
2. Fluorescent lamp of low color temperature
3. Fluorescent lamp of high color temperature
4. Sunlight
5. Cloudiness
6. Other

For 0 to 5, the values increase with increasing color temperature (approx. 1000 - 2000K for Candle to approx. 6500 - 8000K for Cloudiness).

When a white balance setting has not been recorded, a white balance mode may be indicated.

The following white balance modes are supported by the DV standard:

• Automatic
• Hold
• On-Push
• Preset

The decoder will display "AWB" (for Auto White Balance), "HOLD", "PUSH" or "PRESET".

If neither white balance setting nor mode information are present, the decoder will display "-".

Iris

The DV standard permits the f-number to be recorded. The possible values are:

"-" is displayed when no information has been recorded.

Gain

The DV standard defines an "Automatic Gain Control" parameter. In practice, this is the electronic gain that the camcorder applies to the raw, analog signal from the image sensor before digitizing. For many camcorders, this is a manual setting, hence the term "Automatic Gain Control" is a misnoma.

The DV decoder displays the gain in dB, ranging from -3dB to 36dB in 3dB increments, though not all camcorders support this range. When no information has been recorded, the decoder displays "-".

The official DV standard document contains a misprint that omits the formal definition of the range of values. The values used by the DV decoder are based upon Enosoft's analysis of information from a variety of camcorders that are able to display the dB value on the camcorder's display. Since it is possible that the values may be incorrect for some camcorders (though unlikely), the gain values can be configured. See Mapping Gain Values in the Registry for more information.

Color Space Information

Occasionally, it is useful to know what color space is being used for the decoded video. As with most video formats, DV employs a YCbCr-based encoding for the luminance and color information. The Enosoft Enhanced DV Decoder maintains the same format when decoding the video information. Some applications cannot directly process YCbCr (often incorrectly termed YUV) images, hence the decoder can provide the output in a number of formats, including RGB. The choice of color space depends upon a number of factors, including the application using the decoder and, for media player type applications, the hardware capabilities of the computer.

The internal format used by the decoder is Y41P. Additional YCbCr-type formats that are supported are YUY2 and UYVY. Conversion to these formats requires additional computation. No information is lost as a result of the conversion.

For applications that cannot directly process YCbCr-based data, the decoder can convert the native Y41P to 32-bit RGB. In addition to the extra computation required, conversion to the RGB color space can lead to some loss in accuracy of color representation.

Trial Version Spoiler

The time-limited trial version of the Enosoft Enhanced DV Decoder displays a scrolling Enosoft logo near the bottom of the video frame.

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Last Updated on Thursday, May 25, 2006.

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