How to convert MTS to MP4 on Mac (AVCHD camcorder footage)

The camcorder came out of a drawer, or the SD cards turned up in a box, or someone handed you a hard drive labelled “family videos 2009–2014”. You plug it into your Mac expecting a folder of videos and find a folder called PRIVATE containing one item named AVCHD. No clips, no thumbnails. When you do dig the video files out, they’re called 00000.MTS, 00001.MTS, 00002.MTS, and they don’t behave like videos: QuickTime Player is hit-and-miss with them, iMovie wants the original card structure, and almost everywhere you’d send a video expects an MP4.

This guide covers how to convert MTS to MP4 on a Mac: the free iMovie and ffmpeg routes, and the drag-a-folder route for whole cards. All of them run on your Mac with nothing uploaded, which matters for footage like this.

In this guide9 sections

What an .MTS file actually is

AVCHD is the recording format Sony and Panasonic introduced in 2006. Through the following decade it was standard on Sony Handycams, Panasonic camcorders, Canon Vixia and Legria models, and plenty of stills cameras with a video button. Each clip is an MPEG-2 transport stream (the broadcast-style container Blu-ray also uses) holding:

• H.264 video, usually 1920×1080. Early and long-play modes recorded 1440×1080 stretched to widescreen on playback.
• Dolby Digital (AC-3) audio, sometimes 5.1, or uncompressed PCM on some models.

The extension depends on how the file got to you. It’s .MTS straight off the camera, .M2TS after Sony’s desktop software or a Blu-ray authoring tool copied it, and .TS for other transport streams. They’re the same kind of file, and everything below applies to all three.

The key fact is that the video is already H.264, the same codec an MP4 carries. So converting MTS to MP4 doesn’t have to mean re-compressing the picture. The video can often be rewrapped as it is, and only the audio needs converting, because AC-3 is less universally supported than AAC. That puts MTS in the same family as MKV: it’s the container that causes the trouble, not the picture.

Two things about AVCHD are worth knowing before you convert:

• A lot of it is interlaced. Many camcorders recorded 1080i: 50 or 60 fields a second, each holding half the lines. Modern screens are progressive, and depending on the player, interlaced footage can show fine horizontal “combing” on fast motion. Later AVCHD Progressive cameras recorded 1080p and don’t have this problem.
• Long recordings are split. AVCHD cameras cap each file at a few gigabytes (a limit inherited from the FAT32 file system on older SD cards), so a long recording becomes consecutive files (00003.MTS, 00004.MTS…) that belong to one continuous take.

Step zero: get the files off the card properly

Do this before converting anything, whichever method you use:

1. Copy the whole card to your Mac first. Drag the entire PRIVATE folder (or the AVCHD package inside it) into a folder like ~/Movies/Camcorder/Card 01. Converting straight from an old card works, but cards fail, and a copy on your drive is your real archive.
2. Keep one folder per card. Every card starts numbering at 00000.MTS, so three cards give you three different files with the same name. Separate folders keep them apart.
3. To see the clips, right-click the AVCHD item, choose Show Package Contents, and open BDMV → STREAM. The .MTS files are there.
4. Note the dates. The filenames say nothing about when a clip was shot, but each file’s modification date on the card is normally when it was recorded, and a Finder copy keeps that date. Converted files get today’s date, so if chronology matters, the last section of this guide shows a one-line fix.

Method 1: iMovie (free, a few clips at a time)

iMovie reads AVCHD, provided the card’s folder structure is intact:

1. In iMovie, choose File → Import Media and select the card, or your copied AVCHD folder, in the sidebar. iMovie lists the clips with thumbnails.
2. Import the clips you want into an event, then put them in a project.
3. Choose File → Share → File to export an MP4.

The good part is that it’s free, already on most Macs, and it shows you what’s on the card. The bad part is that iMovie is an editor, not a converter: you export a project, it re-encodes everything, and turning 200 clips into 200 separate MP4s is an afternoon of clicking. Loose .MTS files dragged in without the rest of the card structure also often fail to import. iMovie works for a handful of highlights and is a poor fit for an archive.

Method 2: ffmpeg (free, command line, video copied bit for bit)

ffmpeg, installed with Homebrew, gives you the lossless rewrap:

brew install ffmpeg
ffmpeg -i 00000.MTS -c:v copy -c:a aac -b:a 192k 00000.mp4

-c:v copy moves the H.264 video into the MP4 untouched, so a clip converts in seconds with zero picture loss. -c:a aac -b:a 192k converts the AC-3 audio to AAC, which everything plays. For a whole card, send the output to its own folder:

cd ~/Movies/Camcorder/"Card 01"/PRIVATE/AVCHD/BDMV/STREAM
mkdir -p ~/Movies/Camcorder/"Card 01 MP4"
for f in *.MTS; do
  ffmpeg -nostdin -n -i "$f" -c:v copy -c:a aac -b:a 192k \
    ~/Movies/Camcorder/"Card 01 MP4"/"${f%.*}.mp4"
done

Two extras that only the command line handles well:

• Joining a split recording. Transport streams can be joined at the file level, so a take split across 00003 and 00004 becomes one MP4 with ffmpeg -i "concat:00003.MTS|00004.MTS" -c:v copy -c:a aac -b:a 192k take.mp4. Only join consecutive files from the same recording.
• Deinterlacing. If a converted 1080i clip shows combing on motion, re-encode it with a deinterlace filter: ffmpeg -i 00000.MTS -vf yadif=1 -c:v h264_videotoolbox -b:v 16M -c:a aac -b:a 192k 00000.mp4. yadif=1 turns each field into a frame, which keeps the smooth 50 or 60 fps motion the camera captured, and h264_videotoolbox uses the Mac’s hardware encoder. The trade-off is a real re-encode, and a slower one.

ffmpeg is free, lossless and scriptable. The cost is that you’re typing paths into a package folder, maintaining the loop, and reading error output when a clip from a damaged card fails.

Method 3: Zumkor (drag the STREAM folder, pick MP4)

For a box of cards or a drive full of AVCHD folders, Zumkor handles it without the Terminal work. It needs macOS 14 or later on an Apple silicon Mac (M1 or later). Zumkor reads AVCHD .MTS and .M2TS, .TS, and DVD .VOB files, and converts them to MP4:

1. Open the copied AVCHD package (Show Package Contents → BDMV) and drag the STREAM folder, or just the .MTS files, into Zumkor.
2. Pick MP4. For camcorder and DVD footage, MP4 is the one destination Zumkor offers.
3. Look at the rows. Each one shows the exact filename it will produce before you convert. When several cards all start at 00000, the default conflict setting, “Rename with a number”, keeps every file instead of replacing one. Converting each card into its own folder is tidier still.
4. Click Convert and choose where the MP4s go. The originals stay where they are.

The details that matter for an archive job:

• A queue holds up to 2,000 files.
• The list is still there next time. It survives unplugging a drive or a memory card, so you can queue several cards’ worth and convert when they’re connected.
• Conversions keep running with the window closed.
• A file whose extension doesn’t match its contents (an .M2TS renamed to something else along the way) still converts.
• Everything runs on your Mac. Nothing is uploaded, and it works with Wi-Fi off. For home videos of your kids, that’s reason enough to keep the job local.

What Zumkor doesn’t offer for this footage. For AVCHD, .TS and DVD files, shrinking, audio extraction, GIFs and subtitles aren’t available, only the conversion to MP4. Once converted, though, the new file is an ordinary MP4. Drag it back in, and you can trim it with the QuickTime-style yellow handles, shrink it under an email limit with the “Fit a size limit” presets (it lands under the cap, or Zumkor tells you the clip can’t fit), or pull the audio out as an MP3. Zumkor also doesn’t join clips: a recording split across two files comes out as two MP4s, so use the ffmpeg concat line above if you want one continuous file.

Pricing: everything is free for 7 days. After that you can keep converting 5 files a day (25 a week) for free, but free videos get a small Zumkor mark, and each row warns you before you convert. For a family archive, the Full Version is a one-time $19.99 purchase. Buy once and keep it forever, with no subscription and no account. It’s shared through Family Sharing, which is handy when the footage belongs to the whole family.

If you’re converting one card and don’t mind Terminal, ffmpeg’s lossless rewrap is free and hard to beat. Zumkor makes sense when there are many cards, when you’d rather drag a folder than type paths into a package, and when the same box also holds old AVI tapes and WMV files from a Windows PC. It converts those too, in the same queue.

Getting the conversion right

• Keep the resolution. AVCHD is 1080 (or 1440×1080 shown as widescreen). Don’t upscale it to 4K, which only makes bigger files with the same detail. Don’t shrink the archive copy either. Make small copies later for sharing.
• Check one fast-motion clip. Before converting fifty cards, convert a clip with movement, like a kid running or a pan across a room, and watch it full screen. If you see combing, use the ffmpeg yadif line for that footage.
• Check a split recording end to end. Play the join point, or the end of one part and the start of the next, and confirm the audio stays in sync.
• Put the dates back. To copy each original’s timestamp onto its MP4, so clips sort by when they were shot, run this in the folder of converted files, pointing at the STREAM folder: for f in *.mp4; do touch -r "/path/to/STREAM/${f%.*}.MTS" "$f"; done. It assumes the MP4s kept the original base names.
• Keep the originals. The copied card structure is the master. Once you’ve spot-checked the MP4s, archive it to a second drive rather than deleting it.

The rest of the camcorder drawer

AVCHD cards rarely come alone. The same box tends to hold DVDs burned on the camcorder or a set-top recorder. Zumkor converts .VOB files that are already on a drive to MP4, but it doesn’t rip discs, so copy the VIDEO_TS folder off an unencrypted home-made DVD with Finder first. The VOB to MP4 guide covers which of those files hold the video and how to join a disc’s parts into one MP4. Older tape-era transfers often come as .avi or .mov files, and QuickTime .mov files that need to be MP4 follow the same drag-and-convert pattern. For what reads and writes what, see the full formats list.

Bottom line

• A few clips, free, no installs: iMovie’s Import Media from the card, then Share → File. It’s fine for highlights and slow for an archive.
• Lossless and free, in Terminal: ffmpeg -i 00000.MTS -c:v copy -c:a aac -b:a 192k 00000.mp4. The video is copied bit for bit, concat: joins split takes, and yadif=1 handles interlaced footage.
• A drawer of cards, no scripts: Zumkor. Drag the STREAM folder, pick MP4, and convert on your Mac into a folder you choose. Free for 7 days, then 5 files a day free, or a one-time $19.99 for everything.

Whichever route you choose, copy the cards first. Old SD cards and camcorder drives are often the only copy of this footage, and once it’s a folder of MP4s on a backed-up drive, it plays in QuickTime and imports into Photos like any other video.

FAQ

Why can’t I see or open the MTS files from my camcorder on a Mac?

AVCHD camcorders store clips inside a folder structure that Finder shows as a single “AVCHD” package, so the videos look missing. Right-click it, choose Show Package Contents and open BDMV, then STREAM to find the .MTS files. Even then QuickTime Player is hit-and-miss with them, which is why converting to MP4 is the usual fix.

Can I convert MTS to MP4 without losing quality?

Usually, yes. AVCHD video is already H.264, the codec MP4 uses, so ffmpeg can copy the video stream into an MP4 bit for bit and only convert the Dolby Digital audio to AAC. The exception is interlaced 1080i footage that shows jagged edges on motion: fixing that takes a real re-encode with a deinterlace filter.

How do I convert all the MTS files from a camcorder card at once?

Copy the card to your Mac, open the AVCHD package, and either loop ffmpeg over the STREAM folder in Terminal or drag that folder into Zumkor and pick MP4. Zumkor converts up to 2,000 files in one queue, on your Mac with nothing uploaded, into a folder you choose. Keep each card in its own folder, because every card starts numbering at 00000.