FLV to MXF Converter

Convert FLV to MXF: What This Tutorial Covers

This is for anyone holding old Flash Video (.flv) files that have to go into a professional, file-based workflow — an Avid Media Composer bin, a station's playout or ad-delivery ingest, or a tapeless archive — where the only accepted wrapper is MXF. FLV is a dead end for delivery: Adobe ended Flash Player support on 31 December 2020 and began blocking Flash content on 12 January 2021. MXF (Material Exchange Format) is the opposite kind of format: a SMPTE-standardised professional container, specified in SMPTE ST 377-1. By the end you will have a .mxf those tools will ingest, plus a clear picture of what this conversion can and cannot do to a low-bitrate web clip.

How to Convert FLV to MXF

1. Upload Your FLV File: Drag your .flv onto the page or click "+ Add Files" to browse. Batch upload works, so several Flash clips can be queued and converted with the same settings.
2. Pick the Video Codec: Open Advanced Options. Video Codec starts on MPEG-2, the traditional broadcast essence, and H.264 is the other choice. Audio Codec has a single entry for this target — PCM 16-bit Little Endian — because MXF here carries uncompressed audio.
3. Set Quality Preset, Video resolution, or Trim: Leave File Compression on the "Very High (Recommended)" Quality Preset, or switch it to Specific file size, Constant Bitrate, Variable Bitrate, Constant Quality or Constraint Quality. Use Video resolution → Width x Height to hit an exact delivery frame size, and Trim → Time Range to export one segment.
4. Convert and Download: Click "Convert" and save the .mxf. No sign-up, no watermark.

Walk-through: The Two Decisions That Matter

MXF is only a wrapper. What an ingest server validates is the essence inside it — the video and audio codecs, the frame size, and the frame rate — so step 2 is where this conversion succeeds or fails.

• If you do not have the facility's spec sheet, leave Video Codec on MPEG-2. This is the essence legacy playout servers and archive masters were built around, and it is the safest guess when nobody has told you otherwise.
• If your destination is a modern Avid or Premiere workflow that accepts AVC inside MXF, choose H.264. Many Flash-era FLV files already hold H.264, so staying on H.264 avoids a second, pointless generation of loss down to MPEG-2.
• If the spec lists a frame size, set it explicitly. Use Video resolution → Width x Height (or a Preset Resolution) and type the exact numbers. Broadcast ingest routinely rejects off-spec dimensions even when the file itself is valid.
• If you only need one section, trim in the same pass. Trim → Time Range takes a Start time and a Duration in seconds or HH:MM:SS.sss, which saves wrapping minutes of footage you were going to discard.

One behaviour is worth knowing before you look at the file size. The MXF muxer has a strict limit on frame offsets, so our encoder writes MXF with an intra-only GOP — every single frame is a keyframe. That is friendly to scrubbing and frame-accurate editing, which is what MXF is usually for, but it removes inter-frame compression entirely and makes the output substantially larger than an equivalent long-GOP file. Combined with uncompressed PCM audio, expect a .mxf several times the size of the FLV you started from.

Default Output for This Conversion

FLV and MXF Side by Side

Common Errors and How to Fix Them

• "Avid or my playout server rejects the file" — The wrapper is valid but the essence, frame size or frame rate is off-spec. Re-run with the codec and dimensions from the facility's delivery document; "MXF" on its own is never a complete specification.
• "The MXF is many times bigger than the FLV" — Expected, and unavoidable here. Intra-only video plus uncompressed PCM is far less space-efficient than the compact codecs in a web FLV. The extra bytes buy compatibility, not picture quality.
• "The picture is soft or blocky" — A Flash-era clip is usually low resolution and low bitrate. Re-wrapping cannot add detail that was never captured, and raising the frame size only makes the file bigger.
• "It will not open in QuickTime Player or Windows Media Player" — Those consumer players do not handle MXF. Preview in VLC, or open the file in Avid, Premiere Pro, Resolve or Final Cut Pro.
• "The audio is huge" — PCM 16-bit is uncompressed: 44.1 kHz stereo runs about 1.4 Mbps, roughly 10 MB per minute, regardless of how quiet the source was. There is no compressed audio option for MXF output on this page.
• "My FLV will not convert at all" — Half-finished stream rips and truncated captures may not decode. Try remuxing or repairing the FLV in a desktop tool first, or convert a known-good copy.

When This Doesn't Work

Wrapping a file in MXF gives you a structurally professional container, but it cannot manufacture professional structure the source never had. A plain web FLV has no SMPTE timecode track, no ancillary data, and normally a single stereo pair, so the resulting MXF carries exactly that and no more — it will ingest, but it will not arrive with timecode or with HD detail. For genuine station delivery, match the facility's spec end to end (essence, bitrate, frame rate, audio track layout, metadata) and expect to add timecode in your NLE. And if the real goal is simply to watch or share an old clip, MXF is the wrong direction entirely — convert FLV to MP4 instead, or use the Video Compressor if the problem is file size.

Frequently Asked Questions

What codec does the MXF output use, and why is MPEG-2 the default?

MPEG-2 video with PCM 16-bit Little Endian audio. MPEG-2 in MXF is the pairing traditional broadcast servers and ingest workflows were designed around, which makes it the safest default when the destination spec is unknown. Because a Flash-era FLV holds Sorenson Spark, VP6 or H.264, choosing MPEG-2 is a re-encode into an older codec — fine for compatibility, but it cannot recover detail. If your destination accepts AVC inside MXF, switch Video Codec to H.264 and stay closer to the source essence.

Why is my MXF so much larger than the FLV, and can I stop that?

You can reduce it but not eliminate it. Our encoder writes MXF with an intra-only GOP because the MXF muxer constrains frame offsets, so every frame is stored as a full keyframe with no inter-frame prediction — the same property that makes intra-only essence pleasant to scrub in an NLE. Add uncompressed PCM audio and a .mxf several times the size of the source is normal. To pull it down, switch File Compression to Constant Bitrate or Specific file size, or reduce the frame size under Video resolution.

Can I choose a compressed audio codec such as AAC for MXF?

Not on this page. Audio Codec lists exactly one entry for MXF output — PCM 16-bit Little Endian — which is also what most broadcast MXF profiles expect, so it is rarely a limitation in the workflows that ask for MXF in the first place. Budget for the size: uncompressed 16-bit stereo at 44.1 kHz is about 1.4 Mbps, near 10 MB per minute, independent of the original FLV's audio bitrate.

Will converting to MXF make my clip broadcast-ready?

No, and that is a property of the source rather than a limitation of the converter. MXF standardises the wrapper, not the content: a web FLV brings no SMPTE timecode, no ancillary data and no multi-track audio layout, so the MXF you get is structurally professional but carries only what the FLV held. It will ingest into Avid or a playout server; it will not gain a timecode track or a sharper picture. Real delivery still means conforming to the facility's exact spec.

Which software actually opens an MXF file?

Avid Media Composer, Adobe Premiere Pro, DaVinci Resolve and Final Cut Pro all read MXF, and VLC will play it for a quick check. QuickTime Player and Windows Media Player do not support it natively, so an MXF that "will not open" on a consumer machine is a player limitation and not a broken conversion. That is exactly why MXF is a destination for professional pipelines and not for everyday viewing.

Does the MXF keep the audio from my FLV?

Yes — the soundtrack is decoded from whatever the FLV carried (usually MP3 or AAC, sometimes ADPCM, Nellymoser or Speex) and re-encoded to PCM. Because PCM is uncompressed, nothing further is thrown away at that step, but the loss already baked into the original MP3 or AAC track stays baked in. Converting lossy audio to PCM makes the file bigger; it does not make it sound better.

Can I set an exact frame size and trim in the same pass?

Yes, and for delivery work you usually should. Video resolution → Width x Height takes explicit pixel dimensions so the output matches a spec sheet exactly, and Trim → Time Range takes a Start time and a Duration. Doing both in one conversion avoids a second encode, which matters here because every generation of MPEG-2 or H.264 re-encoding costs a little more quality on already-lossy Flash footage.

Why convert a dead Flash format into a broadcast container at all?

Because the destination demands it. The only sound reason to take a legacy .flv to .mxf is to move Flash-era content into a file-based professional workflow — an Avid edit, an ad-delivery or playout ingest, or a SMPTE-standard archive master — that accepts nothing else. If you want the clip to play on phones, browsers or smart TVs, this is the wrong target and FLV to MP4 is the right one.

How are my files handled, and how long are they kept?

Your FLV is uploaded over an encrypted connection, converted on our servers, and the .mxf is returned to you. Uploads and outputs are deleted automatically a few hours after conversion — no sign-up, no watermark, never shared or made public. Because MXF output is large, the download can take noticeably longer than the upload did.