Settings Dialog Box

The Analogue Capture Settings Tab

Note: The Video feature is only available on the PCI card version of DigiTV

One of the new features of DigiTV is the ability to take the real-time video from the PCI card's input and audio from the sound card's stereo input, and encode them directly into MPEG format.

This means that you can make a recording of whatever you want, be it from a web-cam, security camera, video recorder or set-top-box, in exactly the same way as you would for a TV recording (see Recordings).

Software-only MPEG conversion of analogue video demands an awful lot of processing power. To ensure the processing power requirement is as low as possible we have optimised our encoder using MMX, SSE and 3DNOW instructions where possible.

Because there are so many different parameters that can be fiddled with to get the quality of recording that you require, the setup page for the analogue section can look a little daunting at first, however it is easy to soon become familiar with its function:



Viewing

You can choose to either view the input as it comes into the card, ie raw, or after it has been encoded through DigiTV's software MPEG encoder. If you have selected Video/Audio Passthrough then recording will not be possible as the MPEG encoder will have been taken out of the processing path so that you can see the untouched video.

Using the passthrough has a couple of advantages though:

1/ It uses up much less CPU time because the MPEG encoder is disabled, and
2/ There is no delay in processing, so what you see/hear is exactly what is happening at that time (particularly useful if you're using DigiTV's analogue inputs to route your games console through to your computer monitor - the last thing you want is to see a delay of up to a second between what you do and what is displayed!)


Recording File

The recording filename specifies the destination filename for your analogue recordings. It has to be set for the recordings to be successful. The extension of this file will change automatically depending on whether you want to make a recording with just video, just audio, or both video and audio.


Video

Enabling video compression will ensure that there is a video component to your viewed/recorded stream and will enable all of the associated options.

You can set the aspect ratio to match that of the source material, for example a DVD player may be displaying 16:9 widescreen video squashed up into a 4:3 format (called anamorphic video) so you'll need to set the 16:9 option to un-squash it.

The resolution and bitrate settings are a compromise between taste and available CPU power. With the current revision of software it is not yet possible to encode full resolution (768x576) video at full frame rate (25fps), but settings below these maximum figures should give adequate results. If the original recording is being taken from a VHS player, then encoding at anything above VCD (352x288) resolution would waste CPU time as the original recording will have already lost much of its detail when being stored on tape.

Choose the options based upon the quality of the original video, and what your PC is capable of handling. Higher bitrates will give better quality video, but recordings will take up more space on your hard disk than lower bitrates.

Tests have shown that a 1.8GHz machine can provide real-time conversion for a 320x240 image with stereo sound, and with further optimisation it should be possible to have full-size video (768x576) encodable in real-time on currently available PCs.

Video doesn't have to be limited to the real-time variety. Use the Time-Lapse Video option to tell DigiTV to take a frame every few seconds, minutes or hours. Some very interesting effects can be obtained if the input is taken from a CCD camera, and this feature may be useful for security applications.

Please note that it is not possible to ask DigiTV to take the analogue video from a source other than the DigiTV card itself.


Audio

Setting the Enable Audio Compression option will allow stereo audio from the selected source to be compressed into MPEG format and added to the recorded file. The inputs can be either the microphone input or line input of the selected sound card. The quality of the audio is selectable from the Bitrate dropdown, where 44.1KHz is generally regarded as 'CD' quality.

Encoding the audio into MPEG is much faster than encoding the video, so there is comparably no time penalty incurred when encoding for higher quality audio.