What is M4V and how is it different from MP4?

M4V is Apple's video container format introduced alongside iTunes in 2006. Technically it is a superset of MPEG-4 Part 14 (MP4) — most M4V files are identical to MP4 files at the codec level, using H.264 video and AAC audio. The primary difference is that M4V supports Apple's FairPlay DRM for iTunes Store purchases. Non-DRM M4V files can be renamed to .mp4 and will play normally. QuickTime Player, iTunes, and the Apple TV app all open M4V natively, while some non-Apple players (like older VLC versions) may need configuration.

What is FLV and why is it no longer usable?

FLV (Flash Video) is Adobe's container format designed for the Flash Player plugin, which powered most web video from roughly 2005 to 2015. Adobe discontinued Flash Player on December 31, 2020, and all major browsers removed support. FLV files are now unplayable in Chrome, Firefox, Safari, and Edge without third-party software. Converting to M4V (or MP4) is the only way to make FLV content accessible on modern Apple devices.

Will converting FLV to M4V reduce quality?

If the FLV contains H.264 video and AAC audio, FFmpeg can rewrap it to M4V with -c copy and no quality loss. For Sorenson Spark or VP6 encoded FLV files, re-encoding to H.264 introduces some quality loss. Keep the CRF value low (e.g., -crf 18) to minimize visible degradation. Since FLV source quality is often already limited, the output will generally look comparable to the original.

Can I import the M4V into iTunes or the Apple TV app?

Yes. Open iTunes (or the TV app on macOS Catalina and later), go to File > Add to Library, and select the M4V file. It will appear in your library and can be synced to iPhone or iPad. The file must use H.264 video and AAC audio — FFmpeg's default libx264 + aac output meets this requirement.

Why can't this tool convert the file directly in the browser?

FLV decoding and H.264 encoding require full codec libraries not available in browser APIs. The metadata reader uses the browser's built-in File API and runs entirely on your device. Actual conversion requires a desktop tool like FFmpeg or HandBrake, which has access to hardware acceleration (NVENC, VideoToolbox, QSV) and the full libx264 codec stack.

Is my video file uploaded anywhere?

No. The file inspector uses the browser's File API and URL.createObjectURL(). Your video file never leaves your device — there is no upload, no server processing, and no tracking of any kind.

How do I convert multiple FLV files to M4V at once?

Use FFmpeg in a shell loop. On macOS or Linux: for f in *.flv; do ffmpeg -i "$f" -c:v libx264 -crf 22 -c:a aac -b:a 192k "${f%.flv}.m4v"; done — On Windows PowerShell: Get-ChildItem *.flv | ForEach-Object { ffmpeg -i $_.Name -c:v libx264 -crf 22 -c:a aac -b:a 192k ($_.BaseName + '.m4v') } — HandBrake also supports batch queuing via its Queue feature.

What FFmpeg output extension should I use — .m4v or .mp4?

Use .m4v for iTunes/Apple TV compatibility; both are technically the same container. FFmpeg automatically uses the MP4 muxer for .m4v output. If you encounter playback issues on non-Apple software, rename the file to .mp4 — the content is identical.

FLV to M4V Converter

Name: FLV to M4V Converter
Availability: InStock
Author: Nham Vu

Step-by-step guide for converting FLV video files to M4V format using FFmpeg and HandBrake, plus a client-side FLV file metadata inspector.

Video File Inspector

Select any video file to read its metadata instantly — 100% client-side, nothing uploaded.

Click to choose a video file FLV, M4V, MP4, MOV, AVI…

FLV vs. M4V — Format Comparison

Know what you are converting and why

Feature	FLV	M4V
Developer	Adobe (Macromedia, 2002)	Apple (iTunes, 2006)
Common codecs	Sorenson Spark, On2 VP6, H.264	H.264, H.265, AAC, AC-3
Apple device support	Not supported	Full — iPhone, iPad, Apple TV
iTunes / TV app	Not recognized	Native — import directly
Browser support	None (Flash ended 2020)	Safari native; others via MP4 rename
DRM support	None	Optional Apple FairPlay DRM

FFmpeg (Recommended — full codec control)

Free, cross-platform, most flexible

FFmpeg handles all FLV variants. If your FLV already contains H.264 video and AAC audio, use -c copy for a lossless rewrap. For Sorenson Spark or VP6 sources, re-encode to H.264 with libx264 and output to .m4v.

# Install on Mac via Homebrew
brew install ffmpeg

# Install on Windows via winget
winget install ffmpeg

# Check FLV codec before converting
ffprobe -v quiet -show_streams -select_streams v:0 input.flv

# Lossless rewrap (only if FLV contains H.264 + AAC)
ffmpeg -i input.flv -c copy output.m4v

# Re-encode Sorenson Spark or VP6 FLV to H.264 M4V
ffmpeg -i input.flv -c:v libx264 -crf 22 -c:a aac -b:a 192k output.m4v

# High quality for iTunes — near-lossless, Apple TV compatible
ffmpeg -i input.flv -c:v libx264 -crf 18 -preset slow -c:a aac -b:a 192k -movflags +faststart output.m4v

# Batch convert all FLV files in current folder (macOS / Linux)
for f in *.flv; do ffmpeg -i "$f" -c:v libx264 -crf 22 -c:a aac -b:a 192k "${f%.flv}.m4v"; done

CRF 18 = near-lossless (larger file). CRF 28 = smaller with more compression. Default CRF 22 is a good balance for most FLV content.

HandBrake (GUI — quality-focused encoding)

Free, Windows / Mac / Linux

Download and open HandBrake from handbrake.fr.
Drag your FLV file onto the HandBrake window to load it as the source.
In the Summary tab, set Format to MP4 and check Web Optimized.
Change the output file extension from .mp4 to .m4v in the destination path — HandBrake recognizes both.
Choose a preset — Apple 1080p60 Surround or Apple 720p30 Surround targets Apple devices directly.
In the Video tab, confirm the encoder is H.264 (x264) and set RF quality to 20 (lower = higher quality).
In the Audio tab, confirm the encoder is AAC (CoreAudio or FDK) at 160 kbps or higher.
Click Start Encode. Import the resulting M4V into iTunes or the Apple TV app when done.

The Apple device presets in HandBrake are pre-tuned for the correct H.264 profile and level required by iTunes.

Importing M4V into iTunes or the Apple TV App

Sync to iPhone, iPad, and Apple TV

Open iTunes (Windows / older macOS) or the TV app (macOS Catalina and later).
Go to File → Add to Library (macOS) or File → Add File to Library (Windows).
Select your converted M4V file. It will appear under Movies or Home Videos.
Connect your iPhone or iPad and go to the Device → Movies sync tab.
Check the video you want to sync and click Apply. The M4V will transfer to the device.
For Apple TV, use Home Sharing to stream directly from your Mac or PC library.

If the file does not appear in your library, confirm it uses H.264 video and AAC audio. Run ffprobe output.m4v to verify the codec details.

Summary