Free online MTS to ASF converter

What the MTS format is

MTS is the filename extension commonly used for AVCHD video, a high-definition format based on an MPEG-2 transport stream. MTS files usually contain H.264/AVC video with AC-3 or uncompressed PCM audio, often at 1280×720 or 1920×1080 resolution.

Sony Handycam and Panasonic AVCHD camcorders create MTS files, and camera card structures may store related clips with the .MTS or .M2TS extension. You may encounter them after copying video from an SD card, importing footage from a camcorder, or extracting clips from an AVCHD archive. The extension identifies a container; it does not by itself determine the exact video resolution, frame rate, audio format, or interlacing mode.

What the ASF format is

ASF, or Advanced Systems Format, is a Microsoft media container designed for streaming, playback, and distribution over Windows-based systems. An ASF file can contain Windows Media Video, Windows Media Audio, and some other supported streams; files using the .wmv extension are commonly ASF containers with WMV video.

ASF is useful when a legacy Windows application, media server, embedded player, or device specifically requires the Microsoft container. Its indexed metadata and streaming-oriented design can also suit older network playback workflows. ASF is not a quality upgrade, and modern editing software generally has better support for MP4 or Matroska than for ASF.

How to convert MTS to ASF

Using the built-in online converter

1. Open the free converter on 101convert.com and choose the video conversion function.
2. Upload the .MTS file.
3. Set the output format to ASF.
4. Start the conversion and save the resulting .asf file when processing finishes.

Online conversion is suitable for short, non-confidential clips. Large camera recordings may take longer to upload, and the service must be able to accept the file size and audio streams used by the MTS source.

Using FFmpeg on a computer

FFmpeg provides direct control over codecs, bitrate, resolution, and interlacing. Because broad ASF compatibility is usually better with Windows Media codecs than with the original AVCHD streams, transcode both streams with:

ffmpeg -i input.MTS -map 0:v:0 -map 0:a:0? -c:v wmv2 -b:v 4000k -c:a wmav2 -b:a 192k output.asf

Replace input.MTS with the source filename. The optional ? after the audio mapping prevents failure when the clip has no audio. Increase -b:v 4000k for better image quality or reduce it for a smaller file; 4000 kbit/s is only a starting point and is generally inadequate for preserving high-detail 1080p footage.

To resize while converting, add a video filter such as -vf scale=1280:-2 before the output filename. For interlaced MTS footage that must be made progressive, use -vf bwdif=mode=send_frame; otherwise, retaining the original interlacing may be preferable for an interlaced playback device.

Quality, compatibility, and limitations

Transcoding from H.264 to WMV2 is lossy, so the ASF file cannot retain all source detail. Use a sufficiently high video bitrate and avoid repeated conversions. If the receiving software accepts H.264 inside ASF, stream copying may avoid another generation loss:

ffmpeg -i input.MTS -map 0:v:0 -map 0:a:0? -c copy output.asf

This copy command can fail or produce a file that older ASF players cannot decode because ASF support for particular H.264, AC-3, channel-layout, or metadata combinations varies. The WMV2/WMAV2 command is slower but usually produces a more broadly compatible legacy ASF file.

Check the source frame rate and interlacing before choosing settings. Do not simply rename .MTS to .asf; changing the extension does not change the container or codecs. Preserve the original MTS file because conversion may discard camera metadata, chapter information, subtitles, extra audio tracks, and some surround-channel details.