Reset to defaults
Need help?Why Would Anyone Convert MXF to MXF?
Because "MXF" names a wrapper, not a picture. SMPTE ST 377-1 — currently published as ST 377-1:2019 — specifies how essence, timing and metadata are packaged, and says almost nothing about what codec sits inside. Two files can both be perfectly valid MXF and be completely unreadable by each other's tooling.
So the honest use cases for this route are narrow and specific:
- Change the video codec. Your file carries one thing and the receiving system wants another. This page offers H.264 and MPEG-2 in the Video Codec list.
- Change the frame size. A 4K master needs to become a 1080p or 720p proof.
- Cut a section out. The Trim group takes a start time and a duration.
- Rebuild a file something refuses to open. A rewrite through a clean muxer sometimes fixes a structurally odd MXF, though it is not a repair tool and there is no guarantee.
And one non-use case, stated plainly because people assume it: this is not a rewrap and not a passthrough. Every job fully decodes and re-encodes the video. There is no copy mode. If your file is already the codec and size you need, converting it can only cost you quality.
What the Defaults Actually Do to Your File
The page selects MPEG-2 as the video codec, PCM 16-bit Little Endian as the audio codec (the only audio entry offered), and opens File Compression on Quality Preset. That combination has two behaviours worth knowing before you press Convert.
First, MXF output is forced to GOP 1 — every frame encoded as an intra frame, no prediction between frames. The muxer has strict limits on how far a frame's presentation offset may sit from its decode order, and all-intra sidesteps them entirely. It also makes the file substantially larger. On a 10-second 1280 x 720 clip re-encoded at a fixed quantizer, the all-intra video payload measured about 1.7x the size of the identical encode with a 12-frame GOP — 13.7 MB against 8.2 MB.
Second, Quality Preset on a non-CRF codec works by scaling the source bitrate, and the recommended tier asks for roughly 132% of what the source was already using. Combine that with forced all-intra and the untouched default reliably produces a bigger file than the one you uploaded.
Measured, same 10-second 720p source of 11,235,897 bytes throughout:
| What you do | Output | Versus source |
|---|---|---|
| Nothing — MPEG-2, Quality Preset at Very High | 14,598,713 bytes | 1.30x larger |
| Switch Video Codec to H.264, Constant Quality at 20 | 11,058,745 bytes | about the same |
| Constant Quality or Constraint Quality on MPEG-2 | 8,336,441 bytes | 0.74x — but see below |
That last row needs its footnote. MPEG-2 has no quality-target mode, so when you choose Constant Quality or Constraint Quality the value you set is discarded and replaced with a resolution-derived minimum bitrate. Both modes render a slider running 1 to 31 that opens at 5, and moving it changes nothing while MPEG-2 is selected. The number that gets used instead is this:
| Output frame size | Minimum bitrate MPEG-2 is given |
|---|---|
| Up to 720p (921,600 px) | 2.76 Mbps |
| Up to 1080p (2,073,600 px) | 7.46 Mbps |
| Up to 1440p (3,686,400 px) | 16.59 Mbps |
| Above 1440p | 0.18 bits per pixel at 30 fps, capped at 100 Mbps |
Switch the codec to H.264 and the quality slider becomes real: it re-ranges to 16-51, opens at 23, and every value on it reaches the encoder.
How to Convert MXF to MXF
- Upload Your MXF File: Drop the
.mxfon the page or click "+ Add Files". Several files can be queued and run with the same settings. - Pick a Video Codec: MPEG-2 is selected. Choose H.264 if you want working quality control and a smaller file, or keep MPEG-2 if a broadcast or playout system on the far end demands it.
- Set File Compression and Video Resolution: On H.264, use Constant Quality and its CRF slider (16-51, opens at 23, lower is better). On MPEG-2, use Constant Bitrate, Variable Bitrate or Specific file size, because the quality modes are discarded. Video resolution opens on Keep original.
- Trim and Convert: Trim opens on Unchanged; switch to Time Range for a start time and duration. Click Convert. Files are uploaded over an encrypted connection, re-encoded on our servers, and deleted automatically after a few hours — no sign-up, no watermark.
The 48 kHz Rule That Fails Jobs
The MXF writer implements exactly one PCM sample rate: 48,000 Hz. Feed it audio at any other rate and it stops with only 48khz is implemented and leaves a zero-byte file behind. This is reproducible with nothing but the sample rate changed — a 44.1 kHz source fails, the same source at 48 kHz succeeds.
Most genuine MXF masters are already at 48 kHz, because that is what broadcast and post work at, so a straight MXF-to-MXF job usually sails through. The failure shows up when the MXF was built from consumer material — something that started life at 44.1 kHz from a CD rip, a music bed, or a phone recording. There is no sample-rate control on this page, so the fix has to happen before you upload: convert the audio to 48 kHz first, or rebuild the MXF from a 48 kHz master. Do not assume the converter will resample it on the way in. It will not.
Frequently Asked Questions
Does converting MXF to MXF lose quality?
Yes. There is no passthrough or rewrap mode on this route — the video is fully decoded and re-encoded on every job, so you take a generation loss even when the input and output codecs are the same. That is the strongest reason not to run this conversion unless you actually need something changed. If your file already has the codec, frame size and duration you want, the best thing you can do to it is nothing.
Why is my output larger than the file I uploaded?
Two effects stack. MXF output is forced to all-intra with a GOP of 1, which alone measured about 1.7x the video payload of the same encode with a normal 12-frame GOP; and the default Quality Preset tier asks the encoder for roughly 132% of the source bitrate rather than matching it. On the 10-second sample above, an 11.2 MB input came back at 14.6 MB untouched. Switching to H.264 with Constant Quality, or setting an explicit bitrate on MPEG-2, gets you back below the source.
Why does moving the quality slider do nothing?
Because MPEG-2 is selected and MPEG-2 has no quality-target mode in this pipeline. Both Constant Quality and Constraint Quality are converted to a plain bitrate derived from the output resolution — 2.76 Mbps at 720p, 7.46 Mbps at 1080p — and whatever number you set on the slider is thrown away. Either switch Video Codec to H.264, where the slider works and re-ranges to 16-51, or drive MPEG-2 with Constant Bitrate, Variable Bitrate or Specific file size, all of which do reach the encoder.
Can I keep my file's timecode and MXF metadata?
Not reliably. This is a decode-and-re-encode through a general-purpose muxer, not a metadata-preserving rewrap, so package structure, UMIDs, descriptive metadata and timecode tracks should be assumed lost. If any of that is load-bearing in your workflow — an editorial conform, a delivery spec, an archive with fixity requirements — use a tool designed to rewrap MXF rather than a converter.
Which audio codec will the output carry?
PCM 16-bit Little Endian, and only that. It is the single entry in the Audio Codec list on this page, which reflects what the MXF writer will accept here. Uncompressed PCM is also what most broadcast MXF specifications expect, so this is rarely a limitation in practice — but it does mean a compressed audio track in your source becomes uncompressed on the way out, adding roughly 1.5 Mbps per stereo pair to the file.
Why does the job fail with a zero-byte file?
Almost certainly the audio sample rate. The MXF writer implements 48 kHz PCM and nothing else, so a 44.1 kHz — or 32 kHz, or 22.05 kHz — audio track stops the job outright with only 48khz is implemented, and what lands on disk is a zero-length file rather than a partial one. Check the source with any media inspector; if it is not 48 kHz, resample the audio before uploading.
Is an MXF from this converter Op1a?
Do not assume so. This route writes a general-purpose MXF through a standard muxer; it does not target a particular operational pattern, shim, or broadcast delivery specification. If a facility has handed you a spec sheet naming an operational pattern, an essence container UL and a metadata scheme, a general converter is not the right tool — use whatever your NLE or a dedicated MXF wrapper produces, and validate against the spec.
Should I use MPEG-2 or H.264 here?
H.264 unless something downstream requires MPEG-2. It gives you a working quality control, it compresses far better at the same picture quality, and it copes with all-intra encoding more gracefully than MPEG-2 does. MPEG-2 is the right answer only when the receiving system is a traditional broadcast or playout chain that expects it — in which case that system probably also has a bitrate it wants, which you should set explicitly under Constant Bitrate rather than leaving to the default.
What if I only want to make the file smaller?
Then set the target directly instead of hoping the quality controls will find it. Specific file size takes a value in bytes, KB or MB with an Auto Scale toggle; Constant Bitrate and Variable Bitrate take rates. Remember the all-intra penalty applies whatever you pick, so an MXF will not compress as far as the same content in a long-GOP container. If MXF is not a hard requirement, MXF to MP4 will get dramatically smaller at the same visual quality, and Compress MXF is the dedicated tool if you want to stay in the wrapper.
What happens to my file after conversion?
It is uploaded over an encrypted connection, re-encoded on our servers, and both the upload and the MXF it produced are deleted automatically after a few hours. Files are never shared or made public, there is no account to create, and nothing is watermarked.