What is the AVCHD file format?
AVCHD (Advanced Video Codec High Definition) is a camcorder recording format jointly developed by Sony and Panasonic in 2006. It is primarily a folder hierarchy, not a single file - the .avchd extension is rare in practice. When encountered as a single file, it contains an MPEG-2 Transport Stream identical to an .mts clip, identified by the TS sync byte 0x47 at offset 0 repeating every 188 bytes.
The full AVCHD structure follows a Blu-ray-derived layout under PRIVATE/AVCHD/BDMV/STREAM/. Individual video clips are numbered .mts files; per-clip metadata resides in .clpi files under CLIPINF/; playback order is defined by .mpls playlist files. Video is compressed with H.264/AVC; audio uses Dolby Digital AC-3 or Linear PCM at 48 kHz.
AVCHD 2.0 (2011) extended the specification to support 1080/60p and stereoscopic 3D. A key practical constraint is the 2 GB per-clip limit imposed by FAT32 memory cards; cameras split clips automatically and playlists tie the segments together. When archiving footage, always copy the entire BDMV folder tree - copying only the .mts stream files discards playlist and spanning metadata. Consumer cameras have largely moved to MP4 with H.265/HEVC for 4K capture, making AVCHD primarily a legacy camcorder format.
Security & safety
RISK: LOWAVCHD/MTS is passive compressed video data with no scripting. Opening it is safe. The practical caution is to avoid sketchy 'AVCHD codec pack' or 'AVCHD converter' downloads - VLC and HandBrake are the trusted free tools. A malformed .mts could trigger parser bugs, but this is theoretical for normal camcorder footage.
Format details
in a nutshellPrograms that open AVCHD files
Windows4 apps
VLC media player
Open-source Drag an individual .mts file (from BDMV/STREAM) into VLC for instant playback - no extra codecs needed. 
HandBrake
Open-source Open any .mts clip or the AVCHD folder in HandBrake, choose MP4 preset, enable Deinterlace for 1080i footage, Start Encode. 
DaVinci Resolve
Freemium Import the AVCHD folder for full multi-clip edit with spanning; free version handles AVCHD well.
HD Writer AE (Panasonic)
Free Panasonic's own AVCHD importer - bundled with Panasonic camcorders; imports full AVCHD disc with playlists. 
macOS3 apps
iMovie
Free File > Import Media, select the AVCHD folder or camera; iMovie transcodes AVCHD on import. Built into macOS.
Final Cut Pro
Paid Import the AVCHD camera folder; Final Cut handles spanning clips and playlists natively. 
Linux2 apps
Technical details
deep spec| Format type | BDMV-derived folder hierarchy for camcorder recording; .avchd as a single file is an MPEG-2 Transport Stream |
| Video codec | H.264/AVC (MPEG-4 Part 10) |
| Audio codec | Dolby Digital AC-3 or Linear PCM |
| Transport stream packet size | 188 bytes per packet; sync byte 0x47 at the start of each packet |
| Byte order | Big-endian (MPEG-2 TS packet headers) |
| Audio sample rate | 48 kHz |
| Supported resolutions | 480i, 480p, 720p, 1080i, 1080p (AVCHD 2.0 adds 1080/60p and stereoscopic 3D) |
| Per-clip file size limit | 2 GB (FAT32 memory card constraint; camera splits clips automatically) |
| Color encoding | 8-bit YCbCr 4:2:0 (standard); AVCHD Progressive supports 10-bit in some profiles |
| Encryption | None in standard camcorder AVCHD; some Blu-ray AVCHD implementations use AACS |
| Folder structure | PRIVATE/AVCHD/BDMV/STREAM/ for .mts clips; CLIPINF/ for .clpi metadata; PLAYLIST/ for .mpls order files |
| Developers | Sony Corporation and Panasonic Corporation (joint specification, announced NAB Show 2006) |
| Specification versions | AVCHD v1.0 (2006): 1080i/720p H.264; AVCHD 2.0 (2011): adds 1080/60p and 3D support |
| Released | 2006 (AVCHD specification v1.0, jointly by Sony and Panasonic) |
| Latest version | AVCHD 2.0 (2011, adds 3D and 60p support) |
| Open standard | Yes · royalty-free |
| Specification | en.wikipedia.org |
AVCHD conversions
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