M2V to SWF Converter

M2V to SWF: A Silent Conversion, and Why That Is Correct

An .m2v is an MPEG-2 video elementary stream: picture only, with no container, no index and no audio track. A .swf is the Flash movie container. Put those two facts together and the outcome is settled before you start — the SWF this page produces has no soundtrack, because the source had none to give it. The Audio Codec group on the page lists MP3, which is the only audio codec the SWF muxer supports, but with a video-only source there is nothing for it to encode. We confirmed that on a test conversion: the resulting .swf contained a single flv1 video stream and no audio stream at all.

That is not a fault to work around, it is what an elementary stream is. If you need sound, the audio for a DVD-authored .m2v lives in a separate file made at the same time — an .ac3, .mp2 or .wav — and it has to be brought back in by an editor, not by this converter.

How to Convert M2V to SWF

1. Upload Your M2V File: Drag the .m2v onto the page or click "+ Add Files". Several files can be queued and share one set of settings; this page accepts the .m2v extension.
2. Confirm Video Codec: Video Codec opens on FLV — Sorenson Spark, the H.263-derived codec Flash Video used — with MJPEG as the only alternative, because those are the codecs the SWF container carries here. Audio Codec lists MP3 alone and has no effect on a video-only source.
3. Set File Compression, Video resolution and Trim: File Compression opens on Quality Preset at "Very High (Recommended)"; with FLV selected the alternatives are Specific file size, Constant Bitrate, Constant Quality and Constraint Quality, and the Constant Quality slider is the 1–31 qscale scale, lower being better, opening at 5. Video resolution opens on "Keep original" — read the section below before you leave it there. Trim opens on "Unchanged".
4. Convert and Download: Click Convert and save the .swf. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark.

SWF Cannot Store a Pixel Aspect Ratio — Set the Size Yourself

This is the one setting most people get wrong on this page. DVD-authored MPEG-2 stores non-square pixels: a widescreen NTSC stream is 720 × 480 with a 32:27 pixel aspect and a 16:9 display flag, and the player stretches it at playback. The SWF container has no field for that flag. We converted a 720 × 480 stream carrying a 16:9 display aspect and read the output back — the SWF reported its video as 720 × 480 with no sample aspect ratio and no display aspect ratio recorded at all. Played back, that is 3:2: horizontally squashed.

So the aspect correction has to happen in the pixels. Use Width x Height under Video resolution and give the true display size:

Beware the Preset Resolutions list here: it sets the output height and lets the width follow the source's stored proportions, so choosing "360p" on a 720 × 480 anamorphic stream gives you 540 × 360 — still 3:2, still wrong. Only Width x Height fixes the geometry. Check what you have with VLC or ffprobe and read the display_aspect_ratio field before choosing.

What the Output Actually Is

Adobe ended support for Flash Player on 31 December 2020 and blocked Flash content from running in Flash Player from 12 January 2021, so there is no browser plug-in left to open the result. Convert to SWF when a specific legacy authoring tool, kiosk system or archive expects that container; convert to M2V to MP4 when the goal is a file people can actually watch.

Frequently Asked Questions

Why does my SWF have no sound?

Because the .m2v you uploaded has no sound. An MPEG-2 elementary stream carries the picture only — there is no container structure in which a second stream could live — so there is nothing to re-encode. The MP3 entry in the Audio Codec list is the container's single supported audio codec, not a promise that audio exists. To end up with a soundtrack you need to combine the video with its separate audio file in an editor, then convert the result.

Why is the picture squashed or stretched compared with the DVD?

Because MPEG-2 from a DVD stores non-square pixels and SWF cannot record the aspect flag that corrects them. We measured this: a 720 × 480 stream flagged 16:9 came out as a 720 × 480 SWF with no sample or display aspect ratio recorded, which plays back as 3:2. Set the true display size explicitly with Width x Height — 854 × 480 for NTSC widescreen, 1024 × 576 for PAL widescreen, 640 × 480 for NTSC 4:3.

Why does the Preset Resolutions list not fix the aspect ratio?

Because those presets set only the output height; the width is derived from the source's stored proportions, which are exactly the proportions that are wrong on anamorphic material. Picking "360p" for a 720 × 480 widescreen stream yields 540 × 360 — the same 3:2 error at a smaller size. Width x Height is the only control on this page that lets you state both numbers, which is what anamorphic correction requires.

Will the SWF open in a web browser?

No. Adobe ended Flash Player support on 31 December 2020 and began blocking Flash content from running in Flash Player on 12 January 2021; every major browser removed its Flash runtime around then. No setting changes that. FFmpeg-based players such as VLC and mpv will still open the file, because they read the Sorenson Spark stream inside without needing a Flash runtime. For anything web-facing, convert to MP4.

Why FLV instead of the H.264 I could get elsewhere?

Because the SWF container carries Sorenson Spark (listed as FLV) or MJPEG here, and not H.264. Sorenson Spark is H.263-derived and predates H.264 by years, so it needs considerably more bits to reach a comparable picture. That is a structural cost of targeting SWF, not a setting you can tune around. Start from a high Quality Preset to limit the extra damage on top of the MPEG-2 the source already applied.

What is the 1–31 slider under Constant Quality?

It is a quantiser scale, not the 0–51 constant-rate-factor scale used by H.264. With FLV selected it opens at 5, and lower means better quality — 1 is the finest, 31 the coarsest. The direction of travel is the same as CRF but the numbers mean something different, so a value that would be a sensible CRF is a very different setting here. If in doubt, leave the page on its default Quality Preset instead.

Does converting to SWF remove interlacing from a DVD stream?

No. There is no deinterlacing step anywhere in this pipeline, so an interlaced MPEG-2 source keeps its combing — thin horizontal teeth along moving edges — baked into every re-encoded frame. Sorenson Spark has no interlaced coding mode either, so the fields end up flattened into progressive frames with the comb still visible. Deinterlace in a video editor first if the footage has significant motion.

Can I make an interactive Flash file this way?

No. The output is a Flash container holding a video stream — no ActionScript, no buttons, no timeline symbols. A file converter cannot invent a program from a picture stream. Interactive SWF content requires Flash authoring software and the original project source, which is a different problem and one no conversion solves.

What happens to my uploaded file?

It is uploaded over an encrypted connection, converted on our servers, and both the upload and the finished .swf are deleted automatically after a few hours. Nothing is shared or made public, there is no watermark, and no sign-up is required. Because the encoding runs on our servers rather than your device, the practical limit on a long DVD-length stream is upload size and time.