ASF to AVCHD Converter

ASF to AVCHD: A Locked Codec Pair, and a File That Needs Renaming

AVCHD is the camcorder format Sony and Panasonic introduced jointly in 2006 for consumer high-definition recording: H.264/AVC video and Dolby Digital AC-3 audio multiplexed into an MPEG transport stream. ASF is Microsoft's Advanced Systems Format, the container behind Windows Media — the same structure that .wmv and .wma files use, normally holding Windows Media Video with Windows Media Audio.

Pushing one into the other is a compatibility move, and there is nothing to get wrong on the codec side because there is nothing to choose. What does need explaining is the file you end up with, and what it is not.

How to Convert ASF to AVCHD

1. Upload Your ASF File: Drag the .asf onto the page or click "Add Files" to browse. Several files can be queued and converted with the same settings, each uploaded over an encrypted connection.
2. Leave the Codecs Alone: Video Codec contains one entry, H.264, and Audio Codec contains one entry, AC3. Those are the only two lists on this page because they are what the AVCHD specification permits. There is nothing to configure and nothing to get wrong.
3. Choose a Resolution and Compression Mode (Optional): Video resolution opens on Keep original; Preset Resolutions offers 720p and 1080p among others. File Compression opens on Quality Preset at Very High (Recommended), with Specific file size, Constant Bitrate, Variable Bitrate, Constant Quality and Constraint Quality alongside — Constant Quality is a real CRF here, on a 16-51 scale where lower is better. Trim takes a Start time and Duration in seconds or as HH:MM:SS.sss.
4. Convert and Download: Click Convert and take the file. It is processed on our servers and deleted automatically after a few hours. No sign-up, no watermark.

Walk-through: What the .avchd File Actually Is

The download is named with an .avchd extension, and that deserves an explanation, because AVCHD is a specification rather than a file type. Real AVCHD recordings are named .mts on the camcorder and .m2ts after they are imported to a computer; nothing in the specification ever produces a file called .avchd.

Inside the download is an MPEG transport stream carrying an H.264 video track and an AC-3 audio track — which is exactly the AVCHD stream format. A file produced this way probes as format mpegts, with plain 188-byte transport packets whose sync byte sits at offset 0. The implication is about file associations, not about the data:

• VLC, mpv, MPC-HC and ffmpeg-based tools identify the stream by inspecting it, so they open the file as downloaded.
• Camcorder software, Blu-ray authoring tools and most consumer players decide what to do from the extension. Rename clip.avchd to clip.mts or clip.m2ts and they will pick it up. Nothing is re-encoded by renaming; the bytes are already correct.
• If you would rather not rename anything, ASF to MTS writes the same kind of transport stream with the conventional camcorder extension already on it, and ASF to M2TS writes the post-import naming. Note that those two pages default to AAC audio, so if AC-3 is what you need, either switch the Audio Codec there or use this page and rename.

The second thing to be clear-eyed about is what a loose stream is not. This is not an AVCHD disc or memory card. A player-ready AVCHD volume also needs the BDMV directory structure, the STREAM folder, the clip-information and playlist files and the index metadata — all written by authoring software such as multiAVCHD or tsMuxeR. The file this page produces is the correct input to that step, not a substitute for it. Copying it loose onto an SD card will not make a camcorder recognise it.

AVCHD at a Glance

The Three Transport-Stream Targets Compared

The .m2ts distinction is real rather than cosmetic: the transport-stream muxer infers BDAV framing from the output extension, so .m2ts gets the 192-byte packet layout Blu-ray uses and .mts and .avchd get plain 188-byte packets. Which one an authoring tool wants depends on the tool.

Common Errors and How to Fix Them

• "Nothing on my computer will open the file." The .avchd extension has no file association anywhere. Rename it to .mts or .m2ts, or open it in VLC, which ignores the extension entirely.
• "My camcorder software or Blu-ray player rejects it." Two usual causes: the extension (rename it), or the fact that a loose stream is not a disc. Authoring software has to write the BDMV and STREAM structure before a player treats it as AVCHD media.
• "The picture looks soft after I selected 1080p." A standard-definition Windows Media source has no HD detail to recover; upscaling stretches the pixels it already has. Keep the resolution at or near the source size and spend the bits on quality instead.
• "The file is enormous." A transport stream adds overhead and provides no compression benefit of its own, and "Very High" is a generous preset. Switch File Compression to Constant Bitrate and pick a rate inside the AVCHD envelope, or use Specific file size.
• "The ASF will not convert at all." Most likely DRM. ASF is the container Windows Media DRM was built around, and a protected file cannot be decoded by any converter. Check whether it plays in VLC; if VLC refuses it too, that is your answer.
• "Audio and video drift apart." Some Windows Media files, especially ones captured from streams, carry irregular timestamps. Setting an explicit resolution and a constant bitrate makes the encoder re-time the output cleanly.

When This Doesn't Work

AVCHD is a rigid specification — defined resolution tiers, defined H.264 levels and a 24 Mbit/s ceiling, raised to 28 Mbit/s for 1080/50p and 1080/60p under the 2011 AVCHD Progressive amendment. A non-conforming source has to be constrained to fit, which is why some clips end up downscaled or capped. Just as important, this page produces the stream, not a playable disc; that final step belongs to authoring software. And if the destination is anything other than a camcorder or AVCHD-authoring workflow, remember that ASF to MP4 is almost always the better target — a universally playable file with no renaming, no folder structure and no bitrate envelope to respect.

Frequently Asked Questions

Why does the file have an .avchd extension instead of .mts or .m2ts?

Because AVCHD names a specification rather than a file type — camcorders write .mts and computers use .m2ts once a clip has been imported into a BDMV folder. The .avchd file you download holds the same H.264-in-transport-stream bytes; the extension is a label your workflow may or may not accept. If a tool insists on a different name, rename it. Nothing about the payload changes and no re-conversion is needed.

Why can I not choose AAC or any other audio codec here?

Because AVCHD does not allow it. The option lists on this page contain exactly one entry each: Video Codec is H.264 and Audio Codec is AC3. The specification permits Dolby Digital AC-3 or uncompressed linear PCM and nothing else, so the page offers AC-3 rather than letting you build a file that calls itself AVCHD and then gets rejected by the first hardware player that reads it. If you want AAC in a transport stream — perfectly reasonable when the destination is a computer or a media server — use ASF to MTS, where AAC is the default.

Is the file I download a finished AVCHD disc or memory card?

No. What you get is the AVCHD video stream. A player-ready disc or card also needs the BDMV directory structure, the STREAM folder, the clip-information and playlist files and the index metadata, all of which authoring software writes around your stream. This file is the correct input to that step, not a replacement for it, and copying it loose onto an SD card will not make a camcorder recognise it.

Will converting a standard-definition ASF to AVCHD make it high definition?

No. AVCHD is a high-definition format but it cannot invent detail that was never recorded. Plenty of Windows Media files are 480p or smaller, and selecting 1080p under Preset Resolutions stretches those pixels across a bigger frame, producing a soft, upscaled image in a much larger file. The output is genuinely HD only if the ASF source already was. Stepping up only as far as 720p is the gentler compromise if a device insists on an HD frame.

Why does my Windows Media audio get re-encoded?

Because ASF and AVCHD have no audio codec in common. ASF carries Windows Media Audio, and AVCHD requires AC-3 or linear PCM, so there is no way to keep the original track inside a conforming stream. The video is re-encoded too — even an ASF that already contains H.264 is decoded and compressed again rather than copied through, since this pipeline has no pass-through path.

What bitrate keeps the file inside the AVCHD envelope?

AVCHD caps at 24 Mbit/s, dropping to 18 Mbit/s for material recorded to DVD media, and the 2011 AVCHD Progressive amendment raised the ceiling to 28 Mbit/s for 1080/50p and 1080/60p. Switch File Compression to Constant Bitrate and stay under whichever applies to your target device. For a standard-definition Windows Media source, anything above roughly 8 Mbit/s is spending bits reproducing artefacts the source already had.

What is the difference between the .mts and .m2ts pages?

Framing, not codecs. The transport-stream muxer infers its packet layout from the output extension: .m2ts gets BDAV framing, where each 188-byte transport packet is prefixed with a four-byte arrival timestamp for a 192-byte packet, and .mts and .avchd get plain 188-byte packets with the sync byte at offset 0. Blu-ray structures use the BDAV form. Which one your authoring tool or player expects is worth checking before you commit to a long encode.

Can I convert just one section of a long recording?

Yes. Switch Trim from Unchanged to Time Range and enter a Start time and a Duration, either in plain seconds or as HH:MM:SS.sss. Only that window is decoded and re-encoded, which also makes it the fastest way to test a resolution and bitrate combination before committing to the full file. To split a source into several separate clips instead, use Video Cutter first.

Should I convert my ASF to MP4 instead?

For nearly everything except a camcorder or AVCHD-authoring workflow, yes. MP4 plays on phones, browsers, smart televisions, editors and media servers with no folder structure, no authoring step and no renaming — use ASF to MP4. Pick AVCHD only when a specific device or tool genuinely requires an H.264 transport stream with AC-3 audio. To go the other way and open AVCHD footage somewhere modern, AVCHD to MP4 is the conversion.