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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There is no stream-copy switch on this page. A few pairs copy a compatible video stream into the M4V container without re-encoding it, MKV to MP4 among them, which is quick and loses no quality. Most pairs re-encode the video. 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 the converted M4V starts with no chapters; add markers afterwards with a tool such as MKVToolNix or ffmpeg.
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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Usually not. Most conversions keep one audio track, the one with the most channels (normally the main mix), re-encoded for the M4V container, so commentary and alternate-language tracks are dropped. AVI, WMV, MPEG, FLV, VOB and M4V to MKV keep every track, and so does MP4 to MOV. To keep a different track, remux the FLV with that track first (VLC or ffmpeg can do this), then convert it. 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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On some pairs. MP4 to MOV keeps every text subtitle track. AVI, WMV, MPEG, FLV, VOB and M4V to MKV keep every subtitle track: text subtitles are copied or converted to SRT, and picture-based subtitles such as DVD or Blu-ray ones are copied as they are. MP4, MOV and WebM to MKV keep only the first subtitle track (as ASS), and MP4 to WebM keeps the first one as WebVTT. Other pairs, including MKV to MP4 or MOV and WebM to MP4, drop subtitle tracks, and the converter does not burn them into the picture. Subtitles that are already burned in stay, because they are part of the video frames.
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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It depends on the M4V container. MP4, MOV and MKV output use H.264, which plays on practically every phone, browser and TV. WebM output uses VP9. AVI, WMV and MPEG output use the older codecs those formats were designed for. 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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There is no HDR processing or tone mapping. When the video stream is copied (MKV to MP4 or MOV with the default settings), HDR10 passes through as it is. When the video is re-encoded, the HDR10 mastering metadata is dropped and Dolby Vision or HDR10+ data is not kept, and with a Quality, Resolution or Frame Rate setting some pairs also reduce the video to 8-bit colour, so an HDR FLV can look washed out in the M4V.
