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What is the HDV format? What is the AVCHD format? and what is different between HDV and AVCHD ?
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High-definition (HD) video generally refers to any video system of higher resolution than standard-definition (SD).

AVCHD stands for Advanced Video Codec High Definition. AVCHD is a high definition (HD) camcorder format developed by Panasonic and Sony for use in their consumer camcorders.

AVCHD technology makes it possible for high definition video to be compressed during recording with a compact camcorder. AVCHD is two times as efficient as MPEG-2 and MPEG-4.

Compression is the main difference between HD and AVCHD:

HDV is a video format which records compressed (MPEG-2) video on some HD camcorders at either 720p or 1080i resolutions.

AVCHD is a new format of high definition video which, by using highly efficient compression (H.264), allows an HD camcorder to make long-time recordings of 1080i high definition video. There are AVCHD camcorder models which use a SD card, hard drive or optical disc.

Tech Spec Comparison

AVCHD uses MPEG-4 AVC/H.264 compression and encoding for video recording. HDV, on the other hand, uses MPEG-2 Main Profile @ High-1440. Anyone who has compressed an HD video feed to H.264 and to MPEG-2 High-1440 at the same bit rate will tell you that the H.264 version is noticeably better. And this is the first "rub" to HDV users -- AVCHD uses an almost identical data rate (24 Mbps) -- in an MPEG-2 transport stream wrapper.

There are other video advantages in the AVCHD format. For example, it allows for 16:9 aspect ratio pictures in HD with a raster size of 1920x1080 in addition to the HDV raster sizes of 1440x1080 and 1280x720. At the larger raster size, AVCHD has the potential to produce higher horizontal resolution than HDV. AVCHD recording supports 1080i/24/50/60, as well as 720p/24/50/60. Plus, the new format supports 16:9 and 4:3 SD raster sizes of 720x480 at 60i (NTSC) and 720x576 at 50i (PAL).

Digging a little deeper into the two specs, AVCHD has an advantage over HDV in luminance sampling of 1080 video. With the 1920x1080 raster, AVCHD uses a luminance sampling frequency of 74.25 MHz, compared to HDV's 55.7 MHz. In HDV, the higher luminance sampling frequency is reserved for its 720p recording modes, which may explain why 720p HDV can show higher horizontal resolution than 1080i HDV. When AVCHD is set to use the 1440x1080 raster, however, it appears that the standard requires the use of 55.7 MHz luminance sampling, and that will limit AVCHD's advantage solely to the superiority of H.264 encoding.

AVCHD calls for audio recording Dolby AC-3 for one channel or up to 5.1 channels, with data rates from 64 kbps to 640 kbps, or in PCM up to 7.1 at 1.5 Mbps per 2 channels. HDV is limited to two channels of audio compressed with MPEG-1 layer II to 384 kbps. The difference in audio specs might be a giveaway as to why yet another "consumer" HD format has been introduced.

Last update: 02:04 PM Tuesday, September 4, 2007

 



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