AVCHD discs are incompatible with regular DVD-Video players, but play in many Blu-ray Disc players. A conventional single-layer 12 cm DVD can store 35 minutes of video recorded at the maximum bitrate the AVCHD specification allows for DVD media—18 Mbit/s. Hard disk drive A hard disk drive was added as an optional recording medium to AVCHD specification shortly after the new video standard had been announced. Presently, capacity of built-in HDDs ranges from 30 GB to 240 GB. Pros: Higher capacity than other media types, which allows for longer continuous recording. Cons: Sensitive to atmospheric pressure. The HDD may fail if the camcorder is used at altitudes above . Vulnerable to mechanical shock or fast movement. All HDD-based AVCHD camcorders employ non-removable disks. To transfer video to a computer the camcorder must be connected with a USB cable. Most camcorders require using an AC power adapter for this operation. The sound of moving magnetic heads may be heard in the recorded video when recording in quiet environment. Replacing a damaged HDD requires disassembling a camcorder and cannot be done by a consumer. Solid-state memory card Many AVCHD camcorders employ Secure Digital or "Memory Stick" memory cards as removable recording media. Solid-state memory cards offer rewritable storage in a compact form factor with no moving parts. Panasonic and Sony chose removable flash memory as the sole type of recording media in their professional AVCHD lineups, specifically AVCCAM and NXCAM. Until 2010, Sony insisted on usage of its own memory card format - Memory Stick. Since 2010, Sony has allowed using both Memory Stick as well as Secure Digital cards in its consumer and professional camcorders. Panasonic as well as other manufacturers of AVCHD camcorders use Secure Digital cards as removable flash media. Most models accept Secure Digital High Capacity cards (SDHC), while some models are also compatible with Secure Digital Extended Capacity (SDXC) cards, which offer higher transfer speed and capacity. Pros: Compact and lightweight. Does not require time for spin-up and initialization. Not vulnerable to magnetic fields. Can withstand a wider range of air pressure, humidity and vibration than HDDs. Can be easily backed up to DVD for viewing and for long-term archiving. Can store mixed media content, including still images like snapshot photos and still-frame captures. The recording section contains no moving parts, thus operation is almost silent; also a camera can be made more compact and less prone