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Need help?MOS to TS: A Medium-Format Frame in a 188-byte Packet Stream
A .mos is the raw capture written by Leaf digital backs — the Aptus and Aptus-II line, plus the earlier Valeo and Cantare models, shot on Mamiya, Hasselblad and view-camera bodies. It holds undeveloped sensor data in a TIFF-derived container, which is why it opens in Capture One or Leaf Capture and essentially nowhere else. A .ts is an MPEG transport stream: ISO/IEC 13818-1, fixed 188-byte packets, the packaging DVB and ATSC broadcast, IPTV systems and HLS segmenters are built on.
Nothing about these two formats was designed with the other in mind, and the collision shows up in one number. A transport stream is built around video frame sizes; a Leaf back records tens of megapixels. Reconciling the two is most of what this page is about.
How to Convert MOS to TS
- Upload Your MOS File: Drag the
.mosonto the page or click "+ Add Files". Medium-format raws are large and the upload is the slow part; a whole shoot can be queued and every frame renders with the same settings. - Set Merge Strategy and Image Duration: Merge strategy opens on Merge images — several photos become one transport stream, played back to back in upload order. Video per image writes a separate
.tsper frame. Image Duration opens at 5 seconds and ranges from 1/60 s per frame to 10 seconds per frame. - Choose a Resolution — This Is the Important One: Video resolution opens on Keep original, which is almost never what you want from a medium-format frame. Preset Resolutions sets a height and derives the width from your photo's own aspect; Fixed Resolutions sets an exact frame such as 1920x1080 and pads the difference with the Background Color, which opens on White.
- Convert and Download: Video Codec opens on H.264, and under File Compression the mode opens on Quality Preset at "Very High (Recommended)". Click Convert and save the
.ts. Files upload over an encrypted connection, are developed and encoded on our servers, and are deleted automatically after a few hours. No sign-up, no watermark.
Where the Megapixels Go
Before encoding, every still is normalised and its long edge is capped at 4096 pixels. That cap is absolute — there is no control that raises it — and it applies whatever Video resolution you choose, including "Keep original".
Work the arithmetic through and the consequence is clear: on a 4:3 frame, a 4096-pixel long edge means 4096 x 3072, which is about 12.6 megapixels. A 22 MP Aptus-II 5 loses roughly half its linear detail; a 56 MP or 80 MP back loses far more. Nothing you set on this page recovers it, because the cap is applied on the way into the encoder.
That is only the first reduction. A 4096-pixel-wide H.264 stream is also wider than most transport-stream hardware will decode — broadcast and IPTV decoders are built around 1920 x 1080, and 3840 x 2160 at the top end. So you should choose a resolution deliberately rather than leaving it on "Keep original":
| What you want | Control to use | Result from a 4:3 Leaf frame |
|---|---|---|
| A frame that keeps the photo's own shape | Preset Resolutions at 1080p | 1440 x 1080 — the height is set, the width follows the aspect |
| A standard 16:9 broadcast raster | Fixed Resolutions at 1920 x 1080 | 1920 x 1080 with the 4:3 photo centred and white pillarbox bars filling the sides |
| A specific size for an ingest spec | Width x Height | Exactly what you type; the photo is fitted and padded to it |
| The largest the pipeline permits | Keep original | Long edge 4096 — valid, but beyond most decoders |
If the white bars are wrong for your slate, the Background Color dropdown offers Black and a range of other colours. If you would rather have no bars at all, use a Preset Resolution instead of a Fixed one.
Which Leaf Backs Write .mos
| Generation | Models |
|---|---|
| Aptus-II | Aptus-II 5, 6, 7, 8, 10, 12 and 12R |
| Aptus | Aptus 17, 22, 54S, 65, 65S, 75 and 75S |
| AFi | AFi 5, 6, 7 and AFi-II 6, 7, 10, 10R |
| Valeo | Valeo 6, 11, 17, 17wi, 22 and 22wi |
| Earlier | Cantare, Cantare XY, Volare, DCB-II |
The later Leaf Credo backs moved to Phase One's IIQ format, so if your files end in .iiq rather than .mos, this is the wrong page.
What the Output Is Not
It is not a video of your photograph in any interesting sense. The still is encoded at 1 frame per second and held for the Image Duration you set — a 5-second setting produces a 5.000-second stream containing five identical frames. There is no motion, no pan, no zoom and no transition between images in a merged sequence.
It is also silent, and permanently so: the audio controls are not rendered at all on a still-image source, because there is no soundtrack to encode. A genuine broadcast transport stream normally carries AC-3, MP2 or AAC beside the picture, so a playout system that requires an audio track will need one laid over the file afterwards.
And the development is one-way. The raw is demosaiced to 8-bit sRGB with the back's recorded white balance and a standard tone curve baked in. There is no HDR tone-mapping stage in the pipeline, so a frame you exposed to hold a bright sky may clip where your own Capture One recipe would have held it. Keep the .mos; treat the .ts as delivery.
Frequently Asked Questions
Can I keep my back's full resolution in the transport stream?
No. The long edge is capped at 4096 pixels before encoding and there is no setting that lifts it, so the most a 4:3 Leaf frame can carry into the .ts is about 12.6 megapixels. If full resolution is the point, the target is wrong: MOS to TIFF keeps every pixel losslessly, and MOS to JPG keeps every pixel in a file anything can open.
Why would anyone put a Leaf frame into a transport stream?
The honest answers are narrow. Feeding a single frame as a slate, test card or holding image into a DVB, ATSC or IPTV playout chain; satisfying an ingest system that only accepts .ts; or supplying a still to an older HLS pipeline that segments into transport streams. For anything you intend to watch or share, MOS to MP4 plays natively almost everywhere while a bare transport stream generally does not.
Will the file be silent?
Yes, and there is no way to change that here. The audio controls are suppressed entirely on this page because the source is a photograph. If your destination needs an audio track present — some ingest validators do — add one in an editor after conversion.
What happens to the raw editing latitude?
It is gone from the output. A .mos stores undeveloped sensor data, which is why exposure, white balance and highlight recovery remain adjustable after the shot. Producing video requires demosaicing to ordinary RGB at 8 bits per channel, and once that is done the latitude is not recoverable from the .ts. Develop critically in Capture One and convert the export if colour matters.
Why is my photo surrounded by white?
Because you chose a Fixed Resolution whose shape does not match the frame. A 4:3 Leaf photo placed inside a 16:9 raster leaves bars on the sides, and those bars are filled with the Background Color, which opens on White. Switch the colour, choose a Preset Resolution instead so the width follows your photo's aspect, or pick a fixed size that matches the frame.
Can I make a sequence from a whole shoot?
Yes. Queue the frames and leave Merge strategy on Merge images: each developed photo is encoded back to back into one transport stream, each held for the Image Duration you set. Set a short duration such as 1/24 s or 1/30 s per frame if you want them to behave like consecutive video frames, or several seconds each for a slate sequence. Video per image produces one .ts per photo instead.
Is TS the same as the M2TS on a Blu-ray?
They share a payload but not their framing. A plain .ts uses 188-byte packets; the BDAV variant used by Blu-ray and by AVCHD camcorders prefixes each packet with a four-byte arrival timestamp, making them 192 bytes. This page writes the plain form, which is what broadcast, IPTV and HLS tooling expects. Blu-ray authoring tools want the other one.
Which video codec should I pick?
H.264, which is preselected, or H.265 if the receiving system supports it — those are the two codecs on this page with a working quality control. MPEG-2 is the period-correct choice for legacy DVB and ATSC gear. Avoid MPEG-1, MPEG-4, DivX and Xvid here: none has a CRF mode, and on a still image there is no source bitrate for the preset to scale, so the quality control stops doing anything useful.
One of my files was rejected while others from the same shoot worked. Why?
Leaf backs recorded .mos in more than one variant, including a compressed form that not every raw engine reads, and a card pulled mid-write leaves a truncated file that no decoder can repair. Open the file once in Leaf Capture or Capture One and re-save it, or export a 16-bit TIFF and convert that instead.
What happens to my raw file after conversion?
It is uploaded over an encrypted connection, developed and encoded on our servers, and both the upload and the output are deleted automatically after a few hours. Nothing is shared or made public, no account is required, and no watermark is applied. The MOS converter hub lists the other targets available for these files.