Free online MTS to FLV converter

AVCHD camcorders save footage as MTS, but a legacy player, streaming system, or editing application may require FLV. Converting is also useful when a smaller, web-oriented copy is needed, although current browsers generally work better with MP4.

What the MTS format is

MTS is a filename extension commonly used for AVCHD video from Sony, Panasonic, Canon, and other HD camcorders. It is an MPEG-2 transport stream that usually contains H.264/AVC video and AC-3 or AAC audio, often at 720p, 1080i, or 1080p. Camera card folders may contain MTS clips alongside other AVCHD files, and video editors such as Adobe Premiere Pro and DaVinci Resolve can import them.

What the FLV format is

FLV is a container created for Flash-based web video. It can contain H.264 video with AAC audio, as well as older Sorenson Spark and On2 VP6 video. FLV was optimized for legacy browser players, progressive downloads, and Flash streaming servers, and its codecs and bitrate settings could produce relatively compact files. Adobe ended Flash Player support in 2020, so FLV is now mainly appropriate when a specific older player, application, or media server requires it; MP4 with H.264 video and AAC audio is usually more compatible with current browsers, phones, televisions, and editing software.

How to convert MTS to FLV with FFmpeg

FFmpeg is the most controllable desktop option for Windows, macOS, and Linux. It can read the transport-stream container and encode a broadly supported H.264/AAC combination inside FLV.

1. Install FFmpeg from a trusted package source and place the MTS file in an accessible folder.
2. Open Command Prompt, PowerShell, or Terminal, then change to that folder or use complete file paths.
3. Run this command, replacing the filenames as needed:

ffmpeg -i input.mts -c:v libx264 -preset medium -crf 23 -c:a aac -b:a 128k -f flv output.flv

The CRF value controls H.264 quality: lower values preserve more detail and create larger files. Values around 18–28 are a practical range. The command re-encodes both streams, which improves compatibility but takes longer and can reduce quality.

Many camcorders record interlaced 1080i video. If the destination player does not handle interlacing correctly, deinterlace while encoding:

ffmpeg -i input.mts -vf yadif -c:v libx264 -preset medium -crf 23 -c:a aac -b:a 128k -f flv output.flv

Use the first command when the target supports interlaced playback; use yadif when progressive output is required. To reduce the file size further, add a lower resolution such as -vf "yadif,scale=-2:720", but scaling discards detail.

Using a graphical converter

Some desktop video converters expose FLV as an output container. Open the MTS file, select FLV, choose H.264 video and AAC audio when those options are available, set an output filename ending in .flv, and start the conversion. Check the program's current format list before installing it: current releases of tools such as HandBrake generally do not provide FLV export, so its older instructions are not reliable. VLC can play many MTS files, but it is not the preferred choice for controlled FLV encoding.

Using the online converter

You can convert the file on 101convert.com for free without installing software. Upload the MTS file, select FLV as the target format, start the conversion, and download the resulting file. Do not upload confidential footage unless the service's storage and deletion policies meet your requirements.

Quality and compatibility limits

• Re-encoding is normally required; changing the filename or container alone does not reliably convert AVCHD video to a compatible FLV file.
• Keep the original MTS file because every lossy encode can remove detail, and repeated conversions compound the loss.
• AC-3 audio, interlaced video, unusual frame rates, and high bitrates can fail in older FLV players. H.264 video with AAC audio and a moderate bitrate is the safest FLV combination.
• Test the output in the exact legacy player or server that will use it. If there is no FLV-specific requirement, create an H.264/AAC .mp4 instead for current-device compatibility.