DV Capture

In this tutorial and trouble-shooting guide, we'll show you how to capture video from your camera or other DV device on Linux using the Mainactor DV Capture Tool.

In the current version of the capture tool, only DV sources and output formats are supported. If you wish to use another type of source or file format, you will find some information here.

Before you start the capture process, you should ensure your device is connected and the relevant drivers are loaded. If you are unsure about the drivers required, the tool will provide some useful information which may assist in configuring your system.

To start the tool, select the DV Capture tool from the Tools menu. You must select a Capture Driver by selecting from the list provided:

Note that not all of the drivers shown here will be available by default on all systems.

Once a driver is selected, the detected device or devices will be listed in the Capture Device list. This may take a few seconds.

Nothing showing up? Check that your device is turned on and is properly connected. If you have multiple firewire hosts in your system, check the 'Master of the Known Universe' profile, otherwise check the trouble-shooting guide.

You should find that the transport control (located below the preview area) should become active once a device has been located. Normal video devices should be controllable from here without further configuration.

To capture, it is normally sufficient to press the red record button to the right of the tranport controls. If you haven't selected a Capture File, you will be presented with a dialog to specify the directory and file name to use:

The file name you specify doesn't need to include the file extension and the tool will automatically ensure that files are not overwritten by adding a unique 3 digit identifier (so, if you select /home/user/capture, the tool will create files as /home/user/captureNNN.XXX). Similarly, if you select a file such as captureNNN.dif, then the tool will remove the extension and the numeric id and create new files safely.

If your device isn't playing prior to pressing the record button, then it will automatically be started.

For your convenience, you can press the Escape key to hide or show the widgets surrounding the preview area.

Captured files will be registered in your project browser. They will have their own folder name based on the name of the file you specified (so in our example above, all files would be added to a 'capture' folder).

You may control the length of the total capture via the Time settings and the size of each file can be controlled via the File Split Size selection. Scene splitting will be applied if requested - it will force the creation of a new file per recording session from your source.

The tool can be tuned to suit your requirements. The following sections show recommended configurations for various user profiles:

• I have a Camera and some Pre-recorded material
• I have a Camera and want to do Live Captures
• I have an Analogue to DV Converter
• I have Multiple Devices
• I am the Master of the Known Universe

A general trouble-shooting guide can be found here.

I have a Camera and some Pre-recorded material

By default, the tool is configured for this behaviour. You should connect your camera and put it into VCR mode and you can use either the tool transport control or the camera's controls.

I have a Camera and want to do Live Captures

You should connect your camera and place it in Camera or Photo mode and turn the volume down on your computer speakers to avoid feedback.

The default configuration may not be ideal for live capture work since it tries to issue a play command when you start capture - to disable this, enter Capture Settings and turn off 'Play on Capture' (if you don't and you have a tape in your camera it may get overwritten - you have been warned).

I have an Analogue to DV Converter

Typically, Analogue to DV converters behave like cameras so configuration is similar to Camera usage - in the experience of the developers, it is better to disable 'Stop on Close' and 'Play on Capture' for these devices.

I have Multiple Devices

This should just work - by default, it will issue a stop when you change from device to the next (controlled by the 'Stop on Close' flag). If you wish to override this behvaiour and have total control over which device is playing externally to the tool, disable 'Stop on Close' and the 'Play on Capture' flags.

Capturing from multiple suitable devices at the same time is not supported (... at the moment anyway).

I am the Master of the Known Universe

This covers everyone who has any obscure requirements.

If you wish to capture from another PC or non AVC1394 compliant device, disable 'AVC1394 Required', 'Stop on Close' and 'Play on Capture'.

If you have multiple firewire cards and your DV device is not located on the first card, change the 'IEEE1394 Port' accordingly.

If you wish to capture from a non-broadcast channel, then change the 'Channel' accordingly.

Q: DV Capture is reporting that no Drivers are loaded

A: As root, check that either raw1394 or dv1394 are loaded (you can use the lsmod command for this). If neither are loaded, try using modprobe to load them (modprobe raw1394 and modprobe dv1394 - as long as one of them works, you should be able to capture).

Q: DV Capture is reporting that no Drivers are loaded but lsmod says that raw1394 is

A: Check that the permissions of /dev/raw1394 allow access by non-root users.

Q: DV Capture is reporting dv1394 loaded, but it's not working

A: Check that you have /dev/dv1394 device or change the Capture Settings 'Source' setting when the DV1394 driver is selected. More details can be found at linux1394.org.

Q: I've done all that, but I'm still having problems with device configuration

A: Check the documentation on linux1394.org and if that doesn't help, report the issue to the mainconcept linux forum.

Q: Playback is jerky, especially when I maximise the window.

A: Make sure your hardware supports YUY2 accelerated video (you will be able to check that by running the xvinfo command as your normal user). If you have a graphics card produced by nvidia or another closed source oriented manufacturer, check their web site for linux drivers.

Q: I'm seeing badly corrupted video in the preview

A: One persons definition of 'bad' is not the same as anothers - the intention of this section is to resolve issues where the image is broken up, swapped around or mangled in some obvious, non-subtle way. The suggested resolution is to try changing the Video Driver in the Capture Settings from 'accelerated' to 'unaccelerated'.

Q: The preview image looks jagged, wobbly or ugly

A: Most cameras produce interlaced video, as opposed to progressive - this basically means that in every frame, there are actually two frames. The first and second frames are interleaved on alternate rows of each image and while this looks fine on a TV which expects interlaced video, it can look ugly on a PC monitor. The current preview implementation does not offer proper deinterlacing, but you can try changing the Deinterlace option in the Capture Settings to 'top field' or 'bottom field'.

Q: Ouch the audio sounds bad...

A: Select a sensible audio driver, such as dsp or alsa - the default will probably be for esd on many systems and it has a rather annoying habit of sounding squashed and unpleasant.

Q: Whoops - I've messed up - how do I reset to the defaults?

A: Close the tool and remove the .mvl.DVCaptureEngine1.ini file located in your home directory.

Q: How come the capture preview looks better or is smoother than the editor preview?

A: Lots of reasons - mainly it's down to the fact that the capture tool has no effects to apply to the video and we're dealing with the source directly. Note that a computer rendering of a DV stream is quite different to a TV playback and DV simply looks better on a TV.

At the point of writing, the only video that Mainactor will edit directly is DV. This means that if you wish to use a TV card that supports the video4linux driver or an mpeg source such as a DVB card, you will have to capture from these using independent tools and transcode to a DV format to use it in Mainactor. A number of tools exist in the Open Source world for this and it is Mainconcept's intention to provide support for other file formats and codecs in future revisions.