HD on MiniDV

[Bryan Mitchell]

I was hoping that someone could point me in the direction of the most concise answer on a question I have. If an "HD" camera which shoots in 1080 such as the HV10 stores its video on a standard miniDV cassette, how is the picture any better than if it had been shot at the standard resolution?

Thank You,
Bryan

[Chris Hurd]

Originally Posted by Bryan Mitchell

in what ways is the footage superior?

You're asking a relative question that is incomplete. Superior to what? Standard definition?

How an HD camera can store footage on a miniDV cassette is by using an MPEG2-based encoding process which employs interframe compression over a series of images in the video sequence (called a GOP or Group of Pictures, of which there are fifteen if we're talking about 1080i), in contrast to standard DV compression (which is applied one frame at a time). The result is that the recording bandwidth is the same (25 megabits per second) while the size of the frame is much larger (1080 vs. 480).

In other words, how it works is by using a different compression method than DV. Does that help?

[Bryan Mitchell]

Sorry for my incomplete question. Before I saw your answer, I was already rewriting it. Hopefully it is somewhat more clear.

That does help some.

Are these picture groups, groups of two half frames?

[Chris Hurd]

Originally Posted by Bryan Mitchell

If an "HD" camera which shoots in 1080 such as the HV10 stores its video on a standard miniDV cassette, how is the picture any better than if it had been shot at the standard resolution?

I'm not following you... the difference should be obvious between DV (480) and HD (1080).

It doesn't matter that the recording media and bandwidth is the same -- in this case we're talking about a standard Mini DV cassette and 25 megabits per second. What matters is that the HD format going to that tape is using an entirely different encoding process than DV. And that's your short answer.

[Bryan Mitchell]

Does that mean that miniDV is simply inefficient in it's encoding? (I rewrote the original post before reading your response. Please don't take it as my disliking your response or finding it not simplistic enough. I'm simply trying to understand how more video is stored in the same space and if and how there are no sacrifices)

[Chris Hurd]

Does that mean that miniDV is simply inefficient in it's encoding?

No. That means that DV is simply different in its encoding (MiniDV is the tape -- DV is the format).

The primary difference is compression applied to one frame at a time (DV) as opposed to compression applied to a group of frames all at once. If you want an in-depth technical report of how it works, see this link:

http://www.humanvalues.net/hdv/#introduction

And carefully follow through the Introduction and Technical Overview found on that page. Hope this helps,

[Bryan Mitchell]

Thank You Chris.

[Michael Jouravlev]

Originally Posted by Bryan Mitchell

Does that mean that miniDV is simply inefficient in it's encoding?

DV is less efficient than HDV, correct.

Originally Posted by Bryan Mitchell

I'm simply trying to understand how more video is stored in the same space...

How ZIP could pack more than ARC, LZH could pack more than ZIP, and RAR can pack more than ZIP? Better algorithms. How MP3 can pack the same music in much less space than PCM? Lossy compression.

Originally Posted by Bryan Mitchell

...and if and how there are no sacrifices.

There are sacrifices. If you have a drop-out in one frame, you can lose 6 or 15 frames, depending on HDV type. Moving objects may may look worse. For best results, editing should be done on key-frame boundaries.

For more comprehensive answer just search "HDV" on the Net.