Convert FLV to M2TS — Free Online Tool
Convert FLV (Flash Video) files to M2TS (Blu-ray MPEG-2 Transport Stream) format, re-encoding the video with H.264 and audio with AAC — transforming legacy web-streaming footage into a broadcast-grade container suited for Blu-ray authoring, AVCHD-compatible devices, and high-definition archiving.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your FLV 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
FLV files typically carry H.264 or Sorenson Spark video alongside MP3 or AAC audio, all wrapped in Adobe's Flash container. Since M2TS uses an MPEG-2 Transport Stream wrapper incompatible with the FLV container, a full remux is not possible — the streams must be decoded and re-encoded. This tool re-encodes the video using libx264 (H.264) and the audio using AAC, then packages them into the M2TS container. The MPEG-2 Transport Stream structure adds packetization and timing metadata (PCR/PTS) required for Blu-ray and broadcast environments, which FLV entirely lacks. The result is a file that is structurally compatible with Blu-ray authoring tools and AVCHD camcorder workflows, even if the source was originally a low-resolution Flash web video.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary — in this browser-based tool, that is FFmpeg.wasm running entirely in WebAssembly inside your browser, with no server upload involved. On your desktop, this calls your locally installed FFmpeg executable. |
-i input.flv
|
Specifies the input file as an FLV (Flash Video) container. FFmpeg will demux the FLV to extract the raw video and audio elementary streams — typically H.264 or Sorenson Spark video and AAC or MP3 audio — for re-encoding. |
-c:v libx264
|
Re-encodes the video stream using the libx264 encoder, producing H.264 video output. This is necessary because the FLV container cannot be remuxed directly into M2TS; the stream must be decoded and encoded into a transport-stream-compatible form. H.264 is also a valid Blu-ray video codec. |
-c:a aac
|
Encodes the audio stream to AAC using FFmpeg's built-in AAC encoder. Whether the FLV source contained MP3 or AAC audio, it is decoded and re-encoded to AAC — a codec fully supported by the M2TS container and required for AVCHD and Blu-ray compatibility. |
-crf 23
|
Sets the Constant Rate Factor for libx264 to 23, the default balanced quality setting. In the context of this FLV-to-M2TS conversion, this aims to preserve the visual quality of the original Flash video without excessive file size growth; lower values (e.g., 18) improve quality at the cost of larger M2TS files. |
-b:a 128k
|
Sets the AAC audio output bitrate to 128 kilobits per second, a standard quality level appropriate for most speech and general-purpose video audio originally compressed for web streaming in an FLV file. Increase to 192k or 320k if the source FLV contained high-fidelity music or stereo program audio. |
output.m2ts
|
Specifies the output filename with the .m2ts extension, which tells FFmpeg to mux the re-encoded H.264 video and AAC audio into an MPEG-2 Transport Stream container — the format used by Blu-ray discs and AVCHD camcorders — with the packetization and timing metadata that container requires. |
Common Use Cases
- Archiving old Flash-era video content from pre-HTML5 websites into a future-proof, high-definition container before FLV becomes completely unplayable on modern systems.
- Importing FLV footage from legacy screen-recording software or Flash-based webcam captures into Blu-ray authoring software like Encore or Wondershare that requires M2TS input.
- Transferring FLV recordings from older video-sharing platform downloads into an AVCHD-compatible format for playback on Blu-ray players or Sony/Panasonic camcorder-connected TVs.
- Converting FLV game-capture or tutorial recordings into M2TS for inclusion in a Blu-ray disc compilation of instructional content with subtitle track support.
- Preparing FLV broadcast segments originally streamed via Adobe Flash Media Server for ingest into broadcast editing systems that accept MPEG-2 Transport Stream files.
- Consolidating a library of mixed FLV downloads into uniformly structured M2TS files that support multiple audio tracks, making them easier to manage in professional video archiving workflows.
Frequently Asked Questions
No — converting FLV to M2TS re-encodes the video rather than upscaling it, so the output quality is bounded by whatever was in the original FLV file. At the default CRF 23 setting, the H.264 re-encode aims to preserve the source quality as faithfully as possible, but some generation loss is unavoidable since you are decoding a lossy source and re-encoding it. If the original FLV was a low-bitrate web stream at 480p, the M2TS output will still be 480p — just in a Blu-ray-compatible container.
M2TS uses an MPEG-2 Transport Stream container that adds packetization overhead — each 188-byte transport packet includes headers, PCR timing data, and padding that the compact FLV container does not have. Additionally, if the original FLV used aggressive lossy compression for web delivery, re-encoding at CRF 23 with libx264 may produce a higher-bitrate stream than the source in order to represent the decoded frames accurately. You can reduce output file size by raising the CRF value (e.g., to 28 or 30), accepting slightly lower visual quality.
M2TS does support subtitle streams, but FLV does not — FLV has no subtitle track specification, so there is no subtitle data in the source file to carry over. If you need subtitles in your M2TS output, you would need to add an external subtitle file as an additional input in FFmpeg using the -i flag and map it separately. This tool performs a straightforward FLV-to-M2TS conversion and does not add subtitle tracks.
The M2TS container and H.264 video codec are both Blu-ray-compliant, but strict Blu-ray specification compliance also requires specific resolutions (1080p, 720p, etc.), frame rates, and bitrates. If your FLV source was a non-standard web resolution like 854×480 or 960×540, a consumer Blu-ray player may reject it even though the file is technically M2TS. For full Blu-ray disc compatibility you may need to scale the video to a compliant resolution using the -vf scale flag before authoring.
To change video quality, modify the -crf value: lower numbers (e.g., 18) produce higher quality and larger files, while higher numbers (e.g., 28) produce smaller files with more compression. To change audio bitrate, replace 128k in -b:a 128k with a value like 192k or 320k for higher fidelity, or 96k for a smaller file. For example: ffmpeg -i input.flv -c:v libx264 -c:a aac -crf 18 -b:a 192k output.m2ts would give you noticeably sharper video and cleaner audio at the cost of a larger file.
Yes — on Linux or macOS you can use a shell loop: for f in *.flv; do ffmpeg -i "$f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "${f%.flv}.m2ts"; done. On Windows Command Prompt, use: for %f in (*.flv) do ffmpeg -i "%f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "%~nf.m2ts". The browser-based tool processes one file at a time, so the FFmpeg command is particularly valuable for bulk conversions of large FLV archives.
Technical Notes
FLV was designed exclusively for HTTP progressive download and RTMP streaming via Adobe Flash Player, so it carries minimal container-level metadata — no chapter markers, no multiple audio tracks, no subtitle streams, and limited timing precision compared to transport stream formats. M2TS, by contrast, is built on MPEG-2 Transport Stream, a packetized format originally designed for lossy broadcast transmission where packets can arrive out of order; each 188-byte packet carries its own timing and synchronization data. This makes M2TS inherently more robust for archival and disc-based distribution but adds container overhead. The re-encode from FLV to M2TS using libx264 and AAC is a generation-loss operation — if the FLV source used the older Sorenson Spark (FLV1) video codec rather than H.264, quality loss during re-encode may be more noticeable. AAC audio in FLV is preserved in codec type but decoded and re-encoded, resetting encoder state; MP3 audio in FLV will be transcoded to AAC, which is a different lossy format and introduces additional compression artifacts at low bitrates. M2TS does support multiple audio tracks and subtitles, but these features cannot be populated from an FLV source since FLV carries only a single audio and video stream with no subtitle capability.