Step 1: Provide your FLV files using the button above or by toss and let go.
Step 2: Click the 'Convert' button to start the conversion.
Step 3: Fetch your converted M4V files.
FLV to M4V Conversion FAQ
How do I convert FLV to M4V without re-encoding the video stream?
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When the FLV and M4V containers can both carry the same codec (H.264, H.265, VP9, AV1), the converter falls back to a remux: the elementary streams are copied byte-for-byte into the M4V container and only the wrapper changes. A remux of a 1 GB FLV into M4V typically finishes in 5-15 seconds with zero quality loss. FLV typically holds Sorenson Spark or H.264 video with MP3 or AAC audio, wrapped in a stream format designed for RTMP delivery. Structurally an M4V is an MP4 — H.264 or HEVC with AAC — with optional Apple FairPlay DRM and iTunes chapter metadata.
Can I add selectable subtitles once the file is M4V?
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Yes. FLV has no usable soft-subtitle track, so subtitles for FLV content had to be burned into the picture or shipped as a separate sidecar file. M4V carries subtitles as their own selectable stream, so after conversion you can attach an SRT track the viewer can switch on, switch off or restyle.
Can the M4V hold more than one audio track?
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Yes, and it is a real upgrade over FLV. M4V treats every audio stream as a first-class track, so an original-language mix, a dub and a director commentary can live in one file with the player switching between them on demand. M4V keeps chapter markers, artwork and subtitle tracks in the shape the Apple TV app expects, which plain MP4 often loses.
Does M4V support chapter markers that FLV did not?
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It does. M4V stores chapters as container metadata, so a long recording can be navigated by section instead of by scrubbing a progress bar. FLV has nowhere to put that information, so if the source shipped with a chapter list it was in a sidecar file — hand that to the converter and it gets written into the M4V.
Is it worth converting old FLV recordings to M4V at all?
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For anything you intend to keep, yes. FLV belongs to an earlier generation of video tooling and the software that reads it is steadily disappearing from phones, browsers and operating systems. Moving the footage to M4V now, while a clean decoder still exists, is the difference between an archive you can open in ten years and one you cannot. No current browser, phone or TV can play FLV — anything still in this container has to be moved out of it to remain watchable.
Will multi-track audio survive FLV to M4V conversion?
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Yes — every audio track in the FLV (director commentary, alternate languages, descriptive audio) is preserved in the M4V when the target container supports multi-stream audio. MKV and MOV handle unlimited audio tracks; MP4 supports many but some hardware players only see track 1; WebM is capped at one Opus / Vorbis track. M4V is Apple’s variant of MP4, used by iTunes and the Apple TV app for films and TV episodes.
Are subtitle tracks preserved when converting FLV to M4V?
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Soft subtitles (selectable tracks) survive when M4V can carry them: MKV holds SRT, ASS, SSA, PGS, VobSub natively; MP4 only holds mov_text (a stripped-down format). Converting an MKV with ASS styled subs to MP4 will typically downgrade them to mov_text or burn them in. Hardsubs (burned into the video) carry over regardless.
Does FLV to M4V keep chapter markers / DVD-style navigation?
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Chapter metadata transfers between FLV and M4V whenever both containers support a chapter atom (MKV, MP4, MOV). WebM stores chapters in a Matroska-compatible block, so MKV <-> WebM chapters round-trip cleanly. AVI has no chapter spec at all, so an AVI source arrives with no chapters to carry across and an AVI target cannot store the ones it was handed; add markers manually afterwards if you need them.
What about MKV attachments (fonts, cover art) when going FLV to M4V?
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MKV is the only mainstream container that stores arbitrary attached files (TTF fonts for ASS subs, JPG cover art, fan-translated PDF inserts). Going from FLV to M4V drops these attachments when M4V is not MKV — the elementary streams convert, but the attached payload stays in the source. Keep FLV as a backup if you depend on attached fonts.
Which codec does the M4V output use by default?
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The default codec is chosen to match the M4V container conservatively: MKV defaults to H.265 (HEVC) for better compression; MP4 defaults to H.264 for the widest device support; WebM defaults to VP9; AVI uses MPEG-4 ASP (DivX/Xvid lineage). Override via the advanced codec dropdown — AV1 is available for MKV / WebM where you want maximum compression and can wait through the encode. DRM-protected M4V purchases cannot be converted by anything; only unprotected M4V files are convertible, and non-Apple players often need the extension renamed.
How does HDR (HDR10, Dolby Vision) survive FLV to M4V?
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HDR static metadata (HDR10 mastering display values, max content light level) carries through to M4V when both containers and the chosen codec support it (HEVC, AV1 in MKV / MP4). Dolby Vision is more fragile — DV profile 5 / 7 / 8.1 in FLV commonly survives only into MKV with HEVC; converting to an M4V container that does not carry the DV layer flattens to HDR10.
Will the FLV to M4V converter keep variable framerate (VFR)?
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MKV and WebM record real per-frame timestamps and handle VFR natively, so FLV VFR survives into an M4V of those formats with no resampling. MP4 nominally stores timestamps too but some players assume CFR; the converter exposes a "force CFR" toggle that resamples VFR FLV to 24 / 30 / 60 fps M4V for problematic targets.
