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Old Feb 17, 2010, 4:02 AM   #1
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Default An interesting read on AVCHD


This is the standard compression system used for high-definition video onto conventional MiniDV tapes, and supports either 1280 x 720 progressive (720p) or 1920 x 1080 interlaced (1080i) resolutions. HDV uses MPEG-2 compression, and the bit rate after compression is 25 Mbps, which results in very good video quality. MPEG-2 has been known to be susceptible to block noise and errors, but the high bit rate of HDV reduces the risks of these types of issues.
Some "1080i" HDV camcorders have a resolution of 1440 x 1080, while the resolution of others is 1920 x 1080. The maximum resolution after compression onto MiniDV tapes is 1440 x 1080. So any HDV camcorder with a resolution of 1920 x 1080 will be down-converted to 1440 x 1080 to fit onto the MiniDV tape and then up-converted to 1920 x 1080 when displayed.
A camcorder with '24p' resolution mode can record video at 24 progressive frames per second (films/movies are filmed at this rate) in addition to the traditional camcorder video rate of 60 interlaced frames per second. Despite having to be converted to 60 interlaced frames per second when recording onto HDV/MiniDV tapes, the 24p mode should still provide a distinct, film-like look compared to recordings shot in regular 60i mode. This feature is normally found in higher-end camcorders.

This is a new compression system used in DVD and HD-based camcorders which allows the recording of high-definition video onto existing DVD media. AVCHD uses MPEG-4/H.264 compression, which is more efficient (allowing longer recordings onto a smaller amount of disc space) than the MPEG-2 compression used with HDV. Although there are mixed opinions, many experts claim that the video quality of HDV camcorders is superior to current AVCHD-based camcorders, which use a bit rate of 12-15 Mbps (compared to 25 Mbps for HDV), resulting in picture noise and other artifacts in some models.
However, unlike HDV, AVCHD is a dynamic format that can be improved over time as the AVCHD standard has a maximum claimed bandwidth of 24 Mbps. Also, AVCHD does not have the resolution limitations of HDV, which means it can support a full 1920 x 1080 interlaced resolution compared to the unconverted 1440 x 1080 resolution of HDV. Although there are no models currently utilizing this full resolution, this should provide another significant advantage over HDV when AVCHD camcorders with full 1080i resolution become available. This and the superior MPEG-4/H.264 compression lead many experts to believe that AVCHD will eventually surpass HDV/MiniDV in video quality.
Sensor Size/Resolution

Generally speaking, the larger the sensor (or number of sensors) and/or the larger the resolution on the sensor(s), the better the overall video quality. Camcorders either have one or 3 sensors, with the 3 sensor models usually providing increased color fidelity and saturation. There are 2 basic types of sensors in most camcorders, CCD and CMOS:
CCD - CCDs have traditionally been more sensitive to light, which usually produces a better dynamic range along with better overall uniformity. They consume more power then CMOS and are usually more expensive to produce.
CMOS - Traditionally, CMOS sensors were more susceptible to noise, causing poor low-light performance, but camcorder makers have made a great deal of improvements to their CMOS sensors. CMOS also has a faster data transfer rate capability and consumes less power for better battery life.
Although all theses differences are historically true, CMOS sensors are improving with each generation of camcorder, pushing CCD and CMOS sensors closer and closer in their characteristics and performances. Therefore, it is recommended each model is evaluated on its own image quality merits.
Low Light

Lux is a light measurement equal to one lumen per square meter. Every camcorder has a lux rating, which equates to how little light is needed to record an image. So the lower the lux rating, the better the camera performs in low light. However, there is no standard method of producing this rating from brand to brand, so real-world testing and/or reviews are a much better indicator of low-light performance.
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Old Feb 17, 2010, 10:31 AM   #2
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Interesting read. Where is this from?
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