FLV to MKV Converter

Convert FLV to MKV online and see exactly what timed-stream transcoding changes, what MKV still can't promise, and how to verify the result.

Choose Files or drop a video file here Preview it before choosing the output settings

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How FLV turns into MKV: timed-stream transcoding

The picture, sound, and timing streams inside FLV is decoded first, then re-encoded into MKV's own codec and container profile. Duration typically holds steady even as compression, channel mapping, frame cadence, or auxiliary streams shift underneath it. The FLV reader walks timestamped audio, video, and script-data tags, then identifies the legacy codecs and keyframe index before a modern stream is written. Matroska delivery can retain multiple timed tracks, languages, subtitles, chapters, and attachments, though simplified writers and browser players may use only a subset.

Decoded from the legacy Flash Video container historically used for browser streaming. Encoded to a flexible Matroska container capable of multiple audio, video, subtitle, and attachment streams.

INPUT MODEL

FLV

FLV video container

Used for moving images, timed audio, and playback metadata.

Family: Video
MIME: video/x-flv

→

OUTPUT MODEL

MKV

Matroska video

Designed for flexible multi-track video storage.

Family: Video
MIME: video/x-matroska

FLV source facts versus MKV output requirements

FLV

What can fail when FLV video container is interpreted

Current browsers no longer provide native Flash playback, and FLV may contain older codecs with limited hardware decoding.

MKV

What Matroska video cannot safely promise

A simplified conversion may keep only primary streams, and many browsers do not play MKV directly.

ENGINE

How the MKV writer handles this route

The verified MKV profile uses H.264 video and Opus audio when those streams are present.

Acceptance evidence for the converted MKV

BEFORE

Record the FLV evidence before conversion

Inspect codecs, dimensions, frame rate, duration, audio sync, keyframe seeking, and the complete transcoded result.

AFTER

Test the MKV file in its receiving workflow

Inspect the stream list, subtitles, language labels, chapters, seeking, and sync.

Deciding when FLV to MKV is the right conversion

Choose MKV only after the player, editor, or publishing service confirms its container and codecs; keep FLV if extra tracks or source encoding must survive.

What changes between the FLV model and the MKV deliverable

MKV can hold a timed animation, but FLV has no frames to give it; expect a single still frame unless more source material is supplied.
Treat FLV-specific metadata fields as optional in the MKV result until you have actually confirmed they survived.