Step 1: Transfer your MP4 files using the button above or by slide and deposit.
Step 2: Click the 'Convert' button to start the conversion.
Step 3: Retrieve your converted FLV files.
MP4 to FLV Conversion FAQ
How do I re-encode MP4 to FLV without losing video quality?
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Upload your MP4 file and set Quality to High Quality in the conversion options. That re-encodes the video at the highest quality setting (CRF 18 for H.264 and VP9 output), which keeps the most detail at the cost of a larger file. The default, Balanced, uses the standard setting. The FLV output gets a codec its container supports: H.264 for MP4, MOV and MKV, VP9 for WebM. Almost every MP4 in the wild is H.264 video with AAC audio; the container also legally holds HEVC, AV1 and VP9. FLV typically holds Sorenson Spark or H.264 video with MP3 or AAC audio, wrapped in a stream format designed for RTMP delivery.
What happens to the subtitle tracks in my MP4 file?
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They are dropped. FLV has no soft-subtitle stream to hold them, and the converter neither burns them into the picture nor exports them as a separate file. If you need them, extract the subtitles to an .srt file with a desktop tool such as ffmpeg or MKVToolNix before converting, and load that file alongside the FLV in your player. No current browser, phone or TV can play FLV — anything still in this container has to be moved out of it to remain watchable.
Can I still embed the file on a web page after converting MP4 to FLV?
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Not directly. MP4 plays inline in every browser; FLV does not, so a page embedding it falls back to a download link or an empty player frame. If the file is destined for a website, keep the MP4 for the web and treat the FLV as the archive or editing copy.
Will the FLV still play smoothly on a phone or a TV?
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It may not. MP4 is decoded by dedicated silicon on phones, tablets and TVs, which is why it plays without flattening the battery. FLV typically falls back to software decoding on the same hardware — higher CPU load, a warmer device, and dropped frames on 4K material. For a device target, MP4 is the safer container to stay in.
Why would I convert MP4 to an older format like FLV?
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Because a lot of hardware never learned anything newer and never will. DVD players, in-car head units, camcorder playback modes, industrial displays and plenty of broadcast ingest equipment accept FLV and nothing else. The conversion is a deliberate step down in efficiency, bought in exchange for working on a device that has no other option. FLV’s low per-packet overhead made it excellent at streaming over the unreliable connections of its era, and huge archives of it still exist.
Which video codec does the FLV output use?
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It depends on the FLV 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. FLV is the Flash Video container that carried essentially all web video from roughly 2003 until Flash was switched off at the end of 2020.
Will my audio track survive MP4 to FLV conversion?
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Yes, the main audio track comes through, re-encoded to a codec the FLV container plays, for example AAC in MP4 and MOV or Opus in WebM. Most conversions keep only that one track (the one with the most channels), so alternate languages and commentary are dropped. MP4 to MOV, and AVI, WMV, MPEG, FLV, VOB or M4V to MKV, keep every audio track.
Can I keep the original framerate when converting MP4 to FLV?
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Yes. The frame rate is kept unless you change it: a 24 fps MP4 stays 24 fps in the FLV. The Frame Rate setting can also convert to 60, 30 or 24 fps. It changes the rate only; it does not deinterlace the video or remove 3:2 pulldown.
How much will the file size change going from MP4 to FLV?
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It depends on what happens to the video. MKV to MP4 or MOV with the default settings copies the video stream unchanged, so the size stays close to the source. Most other pairs re-encode it: a high-bitrate MP4 usually comes out smaller, while an already heavily compressed one can grow. Smaller File under Quality gives the smallest output, and H.265 in the Codec setting (MP4, MOV and MKV) is usually smaller than H.264 at similar quality but plays on fewer devices.
Will the FLV file play on iPhone, Android, and Smart TVs?
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MP4 with H.264 plays on practically every phone, browser and TV. MOV with H.264 plays on Apple devices and most TVs but not on every older Android phone. MKV needs an app such as VLC on iOS, and WebM is at home in browsers. There is no device preset on this page, so choose the target format your device supports.
How long does converting a 1-hour MP4 video to FLV take?
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There is no fixed time: it depends on the length, the resolution and the target format. Conversions run on our servers' CPUs with software encoders; there is no GPU acceleration. MKV to MP4 or MOV with the default settings copies the video stream and is the quickest. A re-encode to H.264 takes longer, and WebM (VP9) is the slowest target, several times slower than H.264 in our tests.
What is the maximum resolution supported for MP4 to FLV?
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The converter has no resolution cap of its own; the limit is the upload size allowed on your plan, and the resolution stays as it is unless you choose 1080p, 720p or 480p. 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 untouched. A re-encode drops the HDR10 mastering metadata, and with a Quality, Resolution or Frame Rate setting some pairs also reduce the video to 8-bit colour, so an HDR MP4 can look washed out.
FLV (Flash Video) is a video container format developed by Adobe. It is commonly used for online video streaming and is supported by Adobe Flash Player.
