 Here are some frequently asked questions about HDV, editing, shooting, and more.
- What is HDV?
The HDV specification embraces two types of high definition recording, 720p at a video bit rate of 19Mbps, and 1080i at a rate of 25Mbps. A 1080/60i HDV signal (1440 x 1080) is made up of 1080 lines of vertical resolution (number of lines from the top of the screen to the bottom), each line containing 1440 pixels of horizontal resolution, displayed at a rate of 60 interlaced fields, or 30 frames, per second. Standard definition DV records a 480/60i signal (720 x 480) in NTSC countries, which includes the U.S. These resolutions render the HDV uncompressed video bit rate at roughly 4.5x that of consumer DV. In order to reduce the uncompressed video bit rate to DV’s compressed 25Mbps, HDV adopts the same powerful MPEG-2 compression format that is used for digital broadcasts and DVDs. MPEG-2 for HDV combines intra-frame (intra = within frames) compression, used in DV recording with, the more efficient, inter-frame (inter = between frames) compression. Inter-frame compression organizes frames into groups of pictures (GOPs) or frames, where one GOP is equivalent to about 15 frames, or a half-second of video. Each GOP begins with one intra-frame (I-frame) containing a complete frame of video, similar to a frame of DV video, followed by predictive and bi-directional frames which encode only the changes in the incoming video relative to the complete I-frame. By exploring redundancies within each frame, in addition to between frames, the MPEG codec is capable of compression ratios in excess of 20:1, compared to only 5:1 for DV. This means that less than 5% of the uncompressed HDV video signal is actually recorded to tape, compared to 20% with DV. It also means that the impact of missing data with HDV is much greater than with DV. The video bit rates may be similar, but the importance of each recorded bit is not. The interdependency of all the frames in the GOP, to successfully reconstruct the GOP in its entirety, puts greater demands on the tape to maintain bit-for-bit signal integrity during playback. Errors and dropouts can not only compromise the reconstruction of a single frame, but can affect the decoding of the for HDV? Why entire GOP, causing blocks, freeze frames or audio dropouts to occur. HDV needs a high performance tape.
- What is the difference between the Sony and JVC HDV cameras?
- Do I need a new computer to edit HDV?
- How fast does the processor need to be to edit HDV?
- What is an intermediary codec?
- Why don't I want to edit the transport streams?
- What does the intermediary codec do to the transport stream?
- Does the intermediary codec come free with my camera or NLE?
- What is a transport stream? (A ts file?)
- Is the Audio format of HDV any good?
- How do I capture HDV?
- I heard that HDV has .5 second dropouts. Is this true?
- Do I need a new monitor to preview HDV files?
- How does the camera connect to my computer?
- Isn't HDV just too huge a data rate/stream to edit with?
- How do I deliver HDV files to a broadcaster or client?
- I'm confused by HDV and it's colorspace. I'm told it's different than SD. Is this true?
- Can Vegas/Final Cut Pro/Premiere/AVID control my HDV camcorder?
- In Vegas, my HDV images look squeezed. Why?
- In Vegas, I'm not getting 29.97 or 25 fps playback with Cineform intermediary files. Why?
- Is HDV interlaced the same way as DV? Is it upper or lower field first?
- I heard that HDV has bad motion artifacts. What's the scoop?
- Can I edit HDV in real time?
- .:Does the intermediary codec comes free with my camera or NLE?
- What is "Super-HAD?" Sony makes a big deal about it in their advertising.
- When I capture my HDV, its properties are 1440 x 1080 (from the Sony cameras) How come it's not 1920 x 1080; isn't that supposed to be the display size of 1080 HD?
Q: Hi Andrew, how is HDV different from HD?
A: Hi John, the term HD covers the entire spectrum of high definition recording formats. HDV is a subset of HDV, a specific recording format that is an inexpensive way of working with HD. Not all manufacturers support HDV, but it is becoming increasingly popular as an entry level way into the world of HD.
--Andrew Lock
Q: Hi Andrew, I have been wanting to get into high-def but concerned about the cost/benefit, and recently did a little test and was hoping to get your thoughts. I shot a community ballet last month -- the same program on 2 different nights -- using 2 different cameras. On the first night I borrowed a friend's $4000 Sony HDR-FX1 HD camcorder, and used Sony's best Digital Master tape. On the next night I used my tried-and-true Panasonic DVX-100, using Panasonic PQ tape (all tape from Edgewise I should add). I imported both into my PowerMac G5, edited in iMovie HD, burned DVDs on iDVD, and compared the 2 DVDs on 2 TVs in my house (SD and HD). Guess what -- the one shot in HD did not look any better!!!
In trying to figure out what happened, I should note that the ballet program was very long -- almost 2 hours. So is the problem the encoding of a large HD file down onto a small DVD disk? The HD movie file is 71 GB on my hard drive, while the SD movie file is only 25 GB. And of course the DVDs only hold about 4.3 GB. I should also note that I am experienced shooting on my DVX-100, and better at setting the lighting and color controls, etc. It was my first time shooting with the Sony HD camera, so I'm sure I was not optimized on the settings. However, I still would have expected to see better resolution on the DVDs shot with the HD camera.
It was also interesting to note that the HD footage, when viewed in iMovie, looked fantastic -- very sharp and beautiful. So it appears that the problem is in the translation from the NLE system to the DVD. But I need to distribute a good-looking product, not just see it myself on my own computer! So, at this point I really don't see an advantage of buying an expensive HD camera to replace my DVX-100 -- am I missing something?
A: Hi Jeff, your findings are not uncommon. Certainly, the long length of production would have had an adverse affect on the DVD encoding bitrate. However, there are a number of reasons why it is still beneficial to move to HD now:
1. On shorter projects output to DVD you will definitely see the difference in the HD quality footage.
2. If you plan to buy a new HDV camcorder, the small price difference makes it worthwhile and logical to upgrade at this point.
3. Shooting HDV requires different techniques and that need to be learnt, that will take an investment of your time.
4. Alternative HD distribution formats are available even now (such as D-VHS and WMV-HD on DVD), and HD-DVD and Blu-ray are starting to become a reality, so it's a good time to get prepared.
There's much more information about these points in my book, "How to Shoot, Edit & Distribute HDV" available through Edgewise.
--Andrew Lock
Q: Hi Andrew, I'm using Final Cut Express HD to edit and I have found that even the most common fonts once rendered can become fuzzy looking. It seems this is a common problem and I can find no solution other than not going above 16 points on most fonts. Any Advice?
A: Hi GD, I'm not a Final Cut user, so my best guess would be that the either the fonts you are using are too small, or you need to use a different output codec for a sharper image. Remember that TV resolution is very low compared with print, so small fonts will be somewhat fuzzy, that's why text needs to be kept reasonably large. Also, trying a different output codec might produce better results.
--Andrew Lock
Q: Hi Andrew, I make a pretty good living switching events live, saving them directly to a hard drive, doing simple titling and cutting, creating DVD's and selling copies of the final production. Currently I have 6 Canon GL-2's, two Videonics MXPro DV's and of course, all the equipment that allows me to switch events live (I can do two sites simultaneously) I do a lot of concerts, plays, dance recitals etc.
I show many of the events live on big screen projectors. I'd love to switch to HD production, but there seems to be NO HD switcher available except for the Edirol 440-HD. Its $12,000! Is there a switcher that would allow HDV switching via Firewire or some other cabling that is available or will be soon? It seems to be the piece of the puzzle that is missing. The new cameras are available at a reasonable price, the monitors, the editing software, etc. What about a switcher? Any rumors?
A: Hi Dan, you are right that at this time the Edirol is the only unit that will handle HDV switching for live events. I agree that there is a need for a device like that at a cheaper price range. One of the inherent challenges with switching any kind of firewire based signal is that there is a delay on the output, so the video lags behind the audio. That presents a real challenge for doing live i-mag (image magnification of the 'presenter' on big screens at the event. For recording, this issue can be overcome by delaying the audio to match the video. Mixers such as the DataVideo SE-800DV have that feature built-in, but they are still not HDV capable yet. I would guess that Newtek might release a Tricaster type product for HDV but at this time there is no firm news from any of the major companies.
--Andrew Lock
Q: Hi Andrew, I have been thinking of getting into switching, but don't know how to get started. You may recall from the many other times I have pestered you with questions that I do both legal and event video, but am a 1 man shop. But, for example, our school just added football and I was thinking how cool it would be to have something like a big screen, several cams, instant replay, etc. I bought your "How to Shoot Edit & Distribute HDV" book and it was very helpful. Do you have a book on this subject? Are there any others?
A: Hi Jeff, there are many factors to consider regarding switching. Firstly, it's a new skill to learn, and many people overlook this. It takes considerable time to learn how to select which camera to use at any particular time, and many people overlook this - it's not as easy as you might think. There are two main types of systems on the market to consider - direct switching via traditional video hardware, and computer controlled systems. In the former category, Panasonic generally have the best switchers for your market, and the MX-50 is considered an industry standard. In the world of computer switching, NewTek Tricaster is gaining in popularity. Features like instant playback are somewhat advanced and add another layer of complexity. Don't be dissuaded by my comments, I just wanted to let you know what you are getting into. Any new skill can be learned, and there's no reason why you can't do this.
--Andrew Lock
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