Friday, June 4, 2010

About AVCHD>>>>

If you’re not familiar with the new AVCHD codec I’ve outlined some of its technologies with some direct comparisons to the tape-based HDV codec.

Announced in 2006 by Sony and Panasonic, this new industry-standard format is now supported by more than 30 companies and implemented in numerous camcorders, NLE systems, and consumer HD playback devices.

The AVCHD codec is considerably more modern than the older HDV codec. It uses a variety of techniques to achieve greater efficiency than MPEG-2, especially at low bitrates and when dealing with difficult material. AVCHD should be capable of delivering really amazing results but we’ll get into real world performance later on.
What’s beyond debate is that HDV has a resolution of 1440x1080 and uses the MPEG-2 compression codec, while Sony NXCAM or Panasonic AVCHD on the other hand uses full 1920x1080 HD with the more modern MPEG-4 AVC/H.264 codec (H.264 is what Blu-ray and Sky HD broadcasts use). And of course AVCHD’s efficiency makes it ideal for tapeless operation: it uses SD (Secure Digital) and SD/HC (High Capacity) cards, Sony Memory Sticks and other solid-state flash drives such as Sony’s dedicated HXR-FMU128 128GB flash drive.

AVCHD has twice the compression efficiency and considerably improved video performance, especially at lower bitrates, over the older MPEG-2 compression algorithm used in the HDV codec. HDV uses a “constant” bit rate of 25 Mb/s whereas AVCHD camcorders such as the NX5 use a more efficient “variable” bit rate, with a maximum quality setting of 24 Mb/s.
In contrast with MPEG-2 (HDV), in which inter-frame compression based on the correlation between adjacent frames uses fixed blocks of 16x16 pixels, AVCHD divides the blocks into multi-sizes as small as 4x4 pixels. With this method, it is able to use large blocks to process images that show only slight changes on the screen, and smaller blocks to process images that have considerable change. This raises the accuracy of motion compensation, which in turn, boosts the quality of fast-motion images while increasing compression efficiency.