The new AVCHD high definition video standard stores video as files rather than tapes. This is very handy for video/asset management, but runs into a problem with very long clips.

With tape based recording, you can just record for as long as the tape goes. For files, as they get large, they have to be split. This is due to underlying limitations with the file system where the clips are saved (i.e. the memory card or hard disk drive on the camera).

You will find that for large AVCHD clips, the camera will split the files at either the 2Gb or 4Gb mark. AVCHD clips are different to other older video standards in that they are very highly compressed. This is achieved by storing a full image (also known as a keyframe or I-frame) only once, then just storing changes from then on.

When a file is split there is no keyframe at the start of second (and subsequent) clips, so VoltaicHD cannot convert these 'spanned' clips in isolation because they continue on from the previous clip.

Luckily, this is not a big problem. All you have to do is re-join the clips before converting them. Be aware that this will create one large file the size of all the spanned files put together. Make sure you have enough disk space.

Warning: this joined file will take a long time to convert. The converted file will almost certainly not play on your computer due to the file size. You will still be able to edit the file to produce a manageable movie.

Here's how you do it.

File joining on the Mac

The Mac solution requires running a command under the Terminal. Many users will not have had to do this before, but don't worry - its easy. Just follow these steps.

Open a Terminal window. The Terminal application can be found in your Applications folder under Utilities

Go to the directory where your spanned clips are located. You will need to use the Unix change directory command 'cd'

cd Movies/MyAVCHDclips

Enter the following command and press Enter:

cat file001.MTS file002.MTS > newfile.MTS

where file001.MTS and file002.MTS are your files to be joined.

This will take a while! Leave it for at least an hour before checking on your results.

File joining on the PC

Our PC solution uses a command line solution also. Here's what you do.

Open a command window. On XP you do this by going to the Start menu, select Run... enter cmd and click OK.

Go to the directory where your spanned clips are located. You will need to use the change directory command 'cd'

cd c:\Documents and Settings\justin\Desktop\Clips

Now use the copy command to combine the files.

copy /b file001.MTS+file002.MTS newfile.MTS

where file001.MTS and file002.MTS are your files to be joined.

This will take a while! Leave it for at least an hour before checking on your results.