3GPP to AVCHD Converter

3GPP to AVCHD: Read the Extension Note First

AVCHD is the HD camcorder format Sony and Panasonic introduced in 2006: H.264 video and Dolby AC-3 audio carried inside an MPEG transport stream. This page produces exactly that payload — but it names the download .avchd, and .avchd is not an extension camcorders, players or editors recognise. The bytes are a plain MPEG transport stream; the filename is the only thing unusual about them.

So the first thing to know is the fix, and it is a rename. Save the download, change the extension to .mts, and the file becomes the thing your editor is looking for. We verified this by comparing the two directly: the same encode written as .avchd and as .mts came out byte-for-byte identical, and a stream probe reads the .avchd file as "MPEG-TS (MPEG-2 Transport Stream)" without complaint. Nothing is re-wrapped by the rename because nothing needs to be.

How to Convert 3GPP to AVCHD

1. Upload Your 3GPP File: Drag the .3gpp clip onto the page or click "+ Add Files". Several files can queue and convert with one set of settings.
2. Check the Codec Panel — There Is Nothing to Choose: Video Codec lists H.264 alone and Audio Codec lists AC3 alone, because those are the two payloads AVCHD defines. Every other codec is filtered out for this target, so the panel confirms rather than configures.
3. Set Quality and Resolution: File Compression opens on Quality Preset at "Very High (Recommended)", with Constant Bitrate, Variable Bitrate, Specific file size, Constant Quality and Constraint Quality also available. Video resolution opens on Keep original — leave it there for phone footage.
4. Convert, Download, Then Rename to .mts: Click Convert and save the file. Change the extension from .avchd to .mts before handing it to an editor. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark.

Which Extension Should You Rename To?

.mts — not .m2ts. The two are not interchangeable labels for one file, and picking the wrong one is the mistake that wastes an afternoon.

Because the .avchd download is plain 188-byte framing, renaming it to .mts or .ts is honest — the label finally matches the bytes. Renaming it to .m2ts is not: a BDAV file has a different physical structure, and a tool that validates the framing will notice. If .m2ts is genuinely what you need, convert straight to it with 3GPP to M2TS, which writes the 192-byte framing properly. If .mts is what you need, 3GPP to MTS skips the rename step altogether.

AVCHD at a Glance

Common Errors and How to Fix Them

• "My editor will not import the file" — nine times out of ten this is the extension, not the contents. Rename the download from .avchd to .mts and try again.
• "It plays in VLC but my camcorder rejects it" — a camcorder wants the whole BDMV folder structure with its index and playlist files, not a loose stream. A single file cannot be a disc, no matter what it is called. Import it into an AVCHD-authoring tool and let that tool build the structure.
• "The audio sample rate looks wrong" — there is no sample-rate control on this page, so the AC-3 encoder picks the nearest rate it supports to your source. AC-3 offers only 32 kHz, 44.1 kHz and 48 kHz. In our testing a source with an 8 kHz AMR-NB speech track produced a 32 kHz AC-3 track, while a 48 kHz source stayed at 48 kHz. A strict AVCHD importer that expects the 48 kHz audio camcorders record may object to the lower rate.
• "The output is much bigger than my 3GPP" — expected. A 3GPP clip is a low-bitrate mobile recording; AC-3 alone runs at a fixed bitrate regardless of how quiet the source was, and the transport stream adds a header to every packet. In our testing a 402 KB 3GPP clip produced a 639 KB file.
• "It looks like phone footage, not HD" — it is phone footage. See the FAQ below.

Frequently Asked Questions

Why does the file download as .avchd instead of .mts?

Because the output format on this page is named for the AVCHD specification rather than for the extension camcorders write. What comes out is a genuine MPEG transport stream carrying H.264 and AC-3 — the AVCHD payload — but the .avchd suffix itself is not something players and editors are built to recognise. Renaming the download to .mts costs nothing and fixes every downstream tool at once, because the bytes are already exactly what a .mts file contains.

Is renaming safe, or does it corrupt the file?

Completely safe here, and we checked rather than assumed: the same encode written with an .avchd name and with an .mts name compared as byte-for-byte identical, and a stream probe identifies the .avchd file as an MPEG-2 transport stream. Renaming only changes the label the operating system uses to pick a default application. The one rename that would be misleading is to .m2ts, because that spelling implies BDAV 192-byte framing which this file does not have.

Why is there only one video codec and one audio codec to choose from?

Because AVCHD defines them. The specification pairs H.264 video with either Dolby AC-3 or linear PCM audio, and everything else in the converter's normal codec list would produce a file no AVCHD tool would accept. Rather than let you build an invalid file, the page filters the dropdowns down to the legal choices — H.264 and AC3 — so the panel is there to confirm what you are getting, not to configure it.

Will converting my 3GPP clip to AVCHD make it high definition?

No. AVCHD is an HD-oriented format, but the converter can only work with the detail the source recorded, and .3gpp clips are typically QCIF (176x144) or CIF (352x288). Choosing a 1080p resolution preset spreads those pixels across a much larger frame, which produces a bigger file that looks softer rather than sharper. Leave Video resolution on "Keep original" and let your editor scale or window the clip on its HD timeline instead.

Can I burn the result straight to a disc a Blu-ray player will read?

Not from a single file. AVCHD discs need the full BDMV directory structure — index, playlist, clip information and stream folders, all using 8.3 filenames — which is derived from the Blu-ray specification. This converter produces the stream that belongs inside BDMV/STREAM, not the surrounding structure. Feed the renamed .mts to an AVCHD-authoring application, which builds the folders and writes the disc.

What is the difference between .mts and .m2ts, really?

Packet framing, and it is a physical difference rather than a naming convention. An .mts file is a plain transport stream: 188-byte packets, each starting with the sync byte 0x47 at offset 0. An .m2ts file is BDAV-framed: every 188-byte packet is prefixed with a 4-byte arrival timestamp, making 192-byte units with the sync byte at offset 4, and the whole file measures a couple of percent larger as a result. Camcorders write the first spelling; Blu-ray-style layouts use the second. Renaming one to the other changes the label and not the framing.

Should I be converting to AVCHD at all, or to MP4?

MP4 for almost every purpose. It carries the same H.264 video, plays on essentially everything, and needs no folder structure or rename — 3GPP to MP4 is the sensible default. AVCHD earns its place only when a specific camcorder workflow, authoring tool or editing project requires footage in that form, typically so an old phone clip can sit on a timeline beside real camcorder material.

Why does the audio get re-encoded rather than carried over?

Because AVCHD accepts only AC-3 or linear PCM, and a .3gpp clip almost never contains either. Most carry AMR-NB, a narrowband speech codec, or sometimes AAC. Neither is valid in an AVCHD stream, so the soundtrack is decoded and written out as AC-3. For a speech recording that transition is inaudible; for anything musical, remember the source was already band-limited by the handset and AC-3 cannot restore what was never captured.

How long do you keep my uploads?

Your .3gpp file travels over an encrypted connection, converts on our servers, and both it and the file we produce are deleted automatically a few hours later. Nothing is shared or made public and no account is required. Phone clips are small enough that the conversion typically finishes faster than the upload.