Step 1: Attach your MP4 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 M4V files.
MP4 to M4V Optimization FAQ
How do I re-encode MP4 to M4V without quality loss?
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Upload the MP4 file and our converter applies a CRF-based re-encode targeting visually-lossless M4V output (CRF 18 by default, lower = larger / higher quality). The codec is chosen to match the M4V container — H.264 / H.265 / VP9 / AV1 as appropriate.
Which codec does the M4V output use?
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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 M4V conversion runs.
Will my audio track survive MP4 to M4V?
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Yes — audio is re-muxed when MP4 and M4V share an audio codec, or re-encoded to AAC / Opus / Vorbis depending on what the M4V 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 MP4 to M4V?
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By default framerate is unchanged (MP4 24fps stays 24fps in M4V). 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 MP4 and M4V?
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Same-codec re-muxes (H.264 in both MP4 and M4V) 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 M4V file play on iPhone / Android / Smart TV?
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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 MP4 file to M4V take?
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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 MP4 -> M4V finishes in 18-40 minutes; AV1 re-encodes are 2-3x slower.
What is the max resolution supported for MP4 to M4V?
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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 MP4 and M4V containers and codecs support it; SDR sources stay SDR.
Is my MP4 video private during M4V conversion?
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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 MP4 to M4V step?
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Not in the same step — use /video-trim/ or /video-cutter/ to clip the MP4 first, then queue the MP4 -> M4V conversion. Trim-then-convert is faster than re-encoding the whole file just to crop the output.
Why is the M4V file blurry compared to the MP4 source?
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Almost always a bitrate-too-low setting. Re-encoding a high-bitrate MP4 into a lower-bitrate M4V 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 MP4 to M4V converter support subtitles?
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Yes — embedded subtitle tracks (mov_text in MP4, SRT / ASS in MKV, WebVTT in WebM) are preserved when both MP4 and M4V containers support them. Burned-in (hardsub) subtitles transfer automatically because they are part of the pixel data.