Step 1: Attach your MKV files using the button above or by bring and position.
Step 2: Click the 'Optimize' button to start the optimization.
Step 3: Collect your converted FLV files.
MKV to FLV Optimization FAQ
How do I re-encode MKV to FLV without quality loss?
+
Upload the MKV file and our converter applies a CRF-based re-encode targeting visually-lossless FLV output (CRF 18 by default, lower = larger / higher quality). The codec is chosen to match the FLV container — H.264 / H.265 / VP9 / AV1 as appropriate.
Which codec does the FLV output use?
+
It depends on the container. MP4 defaults to H.264 (broadest playback support); MKV defaults to H.265 for ~50% smaller file at the same quality; WebM defaults to VP9 or AV1 (royalty-free web streaming). You can override the codec choice in the advanced options before FLV conversion runs.
Will my audio track survive MKV to FLV?
+
Yes — audio is re-muxed when MKV and FLV share an audio codec, or re-encoded to AAC / Opus / Vorbis depending on what the FLV container supports. Multi-track audio (commentary, alternate languages) is preserved in containers that support it (MKV, WebM, MP4).
Can I keep the original framerate going from MKV to FLV?
+
By default framerate is unchanged (MKV 24fps stays 24fps in FLV). If you need to change it (e.g. interlaced 29.97 to progressive 30fps) the framerate option handles 3:2 pulldown and deinterlacing in the same pass — no second decode required.
What is the file size difference between MKV and FLV?
+
Same-codec re-muxes (H.264 in both MKV and FLV) produce nearly-identical sizes. Codec changes can swing things dramatically: H.264 -> H.265 typically halves the file at the same visual quality; H.264 -> VP9 is roughly comparable; AV1 is currently the smallest at the cost of slower encode time.
Will the FLV file play on iPhone / Android / Smart TV?
+
MP4 / H.264 plays everywhere natively. MOV / H.264 plays on Apple devices and most Smart TVs but not on older Android. MKV needs VLC on iOS. WebM plays in browsers but not most Smart TV apps. The "device compatibility" preset in advanced options picks the safest codec / container for your target.
How long does converting a 1-hour MKV file to FLV take?
+
Depends on the codec change. Same-codec re-mux: 30-60 seconds (no re-encode). Re-encode to a different codec: typically 0.3-0.7x source duration on our GPU pipeline, so a 1-hour MKV -> FLV finishes in 18-40 minutes; AV1 re-encodes are 2-3x slower.
What is the max resolution supported for MKV to FLV?
+
Up to 8K (7680x4320) on Pro. Free is capped at 4K per the file-size limit. HDR metadata (HDR10, Dolby Vision) is preserved where both MKV and FLV containers and codecs support it; SDR sources stay SDR.
Is my MKV video private during FLV conversion?
+
Yes — uploaded video files are processed in isolated workers and deleted within minutes of completion. No human review, no retention beyond the documented window. See /privacy/.
Can I crop or trim during the MKV to FLV step?
+
Not in the same step — use /video-trim/ or /video-cutter/ to clip the MKV first, then queue the MKV -> FLV conversion. Trim-then-convert is faster than re-encoding the whole file just to crop the output.
Why is the FLV file blurry compared to the MKV source?
+
Almost always a bitrate-too-low setting. Re-encoding a high-bitrate MKV into a lower-bitrate FLV at the default CRF compresses motion-heavy scenes heavily. Push CRF down to 16-18 (or set an explicit bitrate ceiling) and re-run to recover quality.
Does the MKV to FLV converter support subtitles?
+
Yes — embedded subtitle tracks (mov_text in MP4, SRT / ASS in MKV, WebVTT in WebM) are preserved when both MKV and FLV containers support them. Burned-in (hardsub) subtitles transfer automatically because they are part of the pixel data.