Convert M2TS to FLV — Free Online Tool
Convert M2TS Blu-ray and AVCHD footage to FLV format for legacy Flash-based web delivery. This tool re-encodes the video using H.264 (libx264) and audio using AAC, stripping the MPEG-2 Transport Stream container and multiple audio tracks down to a single-stream FLV file compatible with Flash Player environments.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your M2TS file here
or click to browse
Free — no uploads, no signups. Your files never leave your browser.
Settings
Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
M2TS files use an MPEG-2 Transport Stream wrapper, commonly carrying H.264 or VC-1 video alongside multiple audio tracks (Dolby TrueHD, DTS-HD MA, or AAC) and subtitle streams. FLV is a much simpler container developed by Adobe that supports only a single video and single audio stream, with no subtitle or chapter support. During this conversion, the video is re-encoded to H.264 using libx264 (even if the source is already H.264, because the transport stream packetization must be unwrapped and repackaged), and the audio is transcoded to AAC at 128k. Any secondary audio tracks, subtitle streams, and broadcast-specific metadata embedded in the M2TS container are discarded. The result is a compact, single-stream FLV file sized for web delivery rather than Blu-ray archival.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary. When run in this browser tool, it executes FFmpeg.wasm, a WebAssembly port that processes your M2TS file entirely client-side without uploading anything to a server. |
-i input.m2ts
|
Specifies the input file in BDAV MPEG-2 Transport Stream format (.m2ts), which may contain multiple video, audio, and subtitle streams as found on Blu-ray discs or AVCHD recordings. |
-c:v libx264
|
Re-encodes the video stream using the libx264 H.264 encoder, which is one of only two video codecs supported by the FLV container — necessary because M2TS may carry VC-1 or other codecs incompatible with FLV. |
-c:a aac
|
Transcodes the audio to AAC, one of only two audio codecs FLV supports. This replaces any high-fidelity audio from the M2TS source (such as lossless TrueHD or DTS-HD MA) with a single lossy AAC stream. |
-crf 23
|
Sets the Constant Rate Factor for libx264 to 23, the default quality level. For high-definition Blu-ray source material, this will produce a significantly lower-bitrate output than the original — lower values like 18 yield better quality at larger file sizes. |
-b:a 128k
|
Sets the AAC audio bitrate to 128 kilobits per second. This is adequate for most speech and music content but represents a substantial downgrade from lossless Blu-ray audio; increase to 192k or 256k if audio fidelity is a priority. |
output.flv
|
Defines the output file with the .flv extension, telling FFmpeg to wrap the re-encoded H.264 video and AAC audio into Adobe's Flash Video container format, discarding all subtitle tracks and secondary audio streams from the M2TS source. |
Common Use Cases
- Publishing Blu-ray rip footage to older Flash-based video platforms or content management systems that only accept FLV uploads
- Embedding AVCHD camcorder footage captured in M2TS format into legacy Flash-based e-learning or presentation software
- Repurposing Blu-ray bonus features or interview clips for older corporate intranet video portals still running Flash Player
- Archiving a web-deliverable copy of M2TS broadcast recordings for Flash-era streaming servers or CDNs that use FLV as the delivery format
- Generating FLV preview clips from high-definition M2TS source material for use in older Flash-based video thumbnail players
- Migrating existing M2TS content libraries to FLV for compatibility with legacy Flash-based kiosk or point-of-sale display systems
Frequently Asked Questions
Yes, some quality loss is unavoidable. M2TS files from Blu-ray often carry lossless or high-bitrate audio (such as Dolby TrueHD or DTS-HD MA) and high-bitrate H.264 or VC-1 video. FLV is a lossy-only format, so both video and audio are re-encoded — video to H.264 at CRF 23 and audio to AAC at 128k. For high-definition Blu-ray source material, the default CRF 23 setting will noticeably reduce the video bitrate compared to the original, so consider lowering the CRF value (e.g., CRF 18) if preserving visual fidelity is important.
They are all discarded. FLV supports only a single audio stream and has no subtitle capability whatsoever. The converter selects the default (first) audio track from the M2TS file and transcodes it to AAC at 128k. If your M2TS contains a director's commentary track, alternate language audio, or embedded PGS/SRT subtitles, none of these will be present in the output FLV. If subtitle preservation matters, FLV is not an appropriate target format.
Although both M2TS and FLV can carry H.264 video, a direct stream copy is not performed here because the H.264 bitstream in an MPEG-2 Transport Stream uses different packetization and timing metadata than what FLV expects. Re-encoding with libx264 ensures the output is properly formatted for the FLV container. This does mean a generation of quality loss occurs on the video, which is an inherent limitation of the M2TS-to-FLV conversion path.
To improve video quality, lower the CRF value — for example, replace '-crf 23' with '-crf 18' for noticeably higher quality at the cost of a larger file. CRF 0 is mathematically lossless for H.264. For audio, replace '-b:a 128k' with '-b:a 192k' or '-b:a 256k' to increase the AAC bitrate. Note that FLV only supports AAC and MP3 audio, so you cannot switch to a higher-fidelity codec like FLAC or Opus in this container.
Yes. On Linux or macOS you can use a shell loop: 'for f in *.m2ts; do ffmpeg -i "$f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "${f%.m2ts}.flv"; done'. On Windows Command Prompt, use 'for %f in (*.m2ts) do ffmpeg -i "%f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "%~nf.flv"'. This is especially useful for processing large Blu-ray rip libraries that exceed the 1GB browser limit of this tool.
FLV is largely obsolete for new projects. Adobe officially ended Flash Player support in December 2020, and all major browsers have removed it. FLV conversion is primarily useful for maintaining compatibility with legacy systems — older CDNs, Flash-based kiosk software, or archived e-learning platforms that have not been updated. For modern web delivery of M2TS content, MP4 with H.264 or WebM with VP9 are far better choices.
Technical Notes
FLV's codec support is highly constrained compared to M2TS: only H.264 or the older Sorenson Spark (FLV native) codec for video, and only AAC or MP3 for audio. This means the rich codec ecosystem of M2TS — including VC-1 video and lossless Dolby TrueHD or DTS-HD MA audio found on commercial Blu-ray discs — cannot be preserved at all. The FLV container also has no support for chapters, subtitle streams, or multiple audio tracks, all of which M2TS handles natively. File sizes will typically be significantly smaller than the source M2TS, as Blu-ray M2TS files routinely reach 20–40 Mbps average bitrate while web-targeted FLV at CRF 23 will be a fraction of that. Note that FLV has a known limitation with timestamps exceeding approximately 596 hours (a 32-bit millisecond overflow), though this is not relevant for typical video content. Metadata embedding in FLV is limited to basic onMetaData tags (duration, framerate, dimensions), so broadcaster or production metadata embedded in the M2TS transport stream will not be carried over.