FAQ's: What is HDV 1 and HDV 2 Format?
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HDV 1 and HDV 2
HDV comes in two flavors, HDV1 and HDV2. However, there are differences: HDV1 from JVC records at 19 megabits per second in MPEG-2 with a resolution of 1280x720 pixels (progressive). HDV2 from Sony and Canon records in MPEG-2 at 25 megabits per second with a resolution of 1920x1080 pixels (interlaced). If you shoot JVC's HDV1, you won't be able to transfer through FireWire from a Sony HDV2 deck or camcorder. Sony's HDV doesn't play back on JVC either. Canon adds to the compatibility issues with an "F" setting on its camcorders that won't play back on either a JVC or Sony deck. In practical terms, this means that you'll either be digitizing directly from your camcorder or committing to HDV1 or HDV2 for your complete production and post chain.
HDV1 and HDV2 Specifications
| HDV1 (720p specification) | HDV2 (1080i specification) |
| Media | DV Tape |
| Video Signal | 720/60p, 720/30p, 720/50p,
20/25p | 1080/60i,1080/50i |
| Number of pixels | 1280 x 720 | 1440 x 1080 |
| Aspect ratio | 16:9 |
| Compression (Video) | MPEG-2 Video (profile & level: MP@H-14) |
Sampling Frequency
for Luminance | 74.25MHz | 55.7MHz |
| Sampling Format | 4 : 2 : 0 |
| Quantization | 8 bits (both luminance and chrominance) |
| Bit rate after Compression | 19Mbps | 25Mbps |
| Audio Compression | MPEG-1 Audio Layer II |
Audio Sampling
Frequency | 48kHz |
| Audio Quantization | 16 bits |
Audio Bit rate
after
Compression | 384kbps |
| Audio Mode | Stereo (2 channels) |
| Stream Type | Transport Stream | Packetized Elementary Stream |
| Stream Interface | IEEE-1394 FireWire (MPEG-2-TS) |
MPEG-2 Compression
DV and HDV compress images very differently. In DV, like HDCAM and Digital Betacam, the video-compression is purely intraframe, comparing and compressing within each individual image. It's the same kind of compression most photos used on the Internet (e.g., JPEG). Each frame is compressed independently. Since HDV is MPEG-2, it uses both intraframe and interframe compression. Interframe compression happens in what is called a GOP or group of pictures, made up of I, B and P frames. The I frame is encoded independently. The next frame to be encoded is a P or predictive frame, which anticipates changes in the video, discarding redundant information. Between the I and P frames, B or bi-directional frames fill in, looking both backwards and forwards. It's played back IBBPBBP etc., with the next I frame determined by the size of your GOP. Since most video has redundancy across frames, the method works well until there is a lot of change. While shooting HDV, be wary of rapid camera motion like fast pans, which can overwhelm the compression process.
Sony also recommends using its better quality HDV vs. DV tape. If you're unlucky enough to have a drop out on a recorded I frame, you have no back up immediately fore and aft. The glitch will affect everything in your GOP.
Advantages of the Two HDV Specifications
HDV1
Temporal resolution is lower, but it is progressive and reflects the
behavior of analog film.
Amount of data is smaller after de-compression which equals more realtime
and lower minimum system requirement.
HDV2
Higher temporal resolution (50/60i), this is positive with faster moving
elements in the picture.
Larger resolution and higher resolution make HDV2 closer to true HD.
Setting up a System
Setting up the best possible system for HDV editing with Liquid is pretty straight-forward.
All it takes is making sure that you have a good mix of quality components.
CPU
Minimum:
For HDV1, Single 2.8GHz. For HDV2 Single 3.0 GHz.
Recommended:
For HDV 1 and HDV 2, Dual 3.0 GHz or Higher
Benefit of more:
To do the math required to edit native HDV the processors play a very important role. The
faster the processor the more streams of HDV you will be able to edit in real-time. Please
note that if you have a slower processor, you can still edit and play back HDV. Lots of
demos of Liquid are done with HDV1 on laptops with a 1.6 GHz Pentium M.
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