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Need help?Convert JPG to FLV: What This Tutorial Covers
FLV is Adobe's Flash Video container. The player it was built for is gone — Adobe ended support on 31 December 2020 and began blocking Flash content on 12 January 2021 — but the container itself is still requested by older content-management systems, e-learning packages, media servers and RTMP-based ingest pipelines, which is why converting a photo into a .flv still comes up. This walk-through covers the settings that actually matter here: which of the four codecs to write, why the default quality control does nothing on the default codec, and what to do when a player refuses the file.
How to Convert JPG to FLV
- Upload Your JPG Files: Drag them onto the page or click "+ Add Files". JPG, JPEG and JFIF are accepted, and Merge strategy decides whether a batch becomes one clip ("Merge images", the default) or one file per photo ("Video per image").
- Set the Duration: In Advanced Options, the Duration dropdown holds each image for 5 seconds by default and can be set from a single frame up to 10 seconds per image.
- Pick the Video Codec and Quality Mode: Video Codec offers FLV (the default), H.264, Flash Video and Flash Video (v2). File Compression offers Quality Preset, Constant Quality and Constraint Quality — the combination matters, and the table below shows which pairings work.
- Convert and Download: Click Convert and save the
.flv. Files upload over an encrypted connection, are processed on our servers, and are deleted automatically after a few hours. No sign-up, no watermark.
Walk-through: Choosing a Codec and a Quality Mode
| Video Codec option | What it really is | Rate control that works | Choose it when |
|---|---|---|---|
| FLV (default) | Sorenson Spark, a Flash-specific derivative of H.263; encodes 4:2:0 only | Constant Quality (1-31, lower is sharper) or Constraint Quality (Max bitrate) | The receiving system is genuinely old and expects classic Flash Video |
| H.264 | Standard AVC muxed into the FLV container | Quality Preset, Constant Quality (CRF 16-51) and Constraint Quality all work | A media server, RTMP ingest endpoint or modern decoder is on the other end |
| Flash Video | Flash Screen Video — a lossless screencast codec that stores RGB, not 4:2:0 | None: rate control is skipped entirely for lossless codecs | Flat UI screenshots or diagrams where exact pixels matter more than size |
| Flash Video (v2) | The second-generation Flash Screen Video codec, also lossless | None | The same use case, where the target supports the later screen codec |
The pairing that traps people is FLV plus Quality Preset — which is the out-of-the-box combination. Quality Preset is a CRF-style control, Sorenson Spark has no CRF, and the fallback path multiplies the source video's bitrate by a quality factor. A still photo has no video bitrate at all, so the target computes to zero and the encoder drops to its own internal floor. Change File Compression to Constant Quality and set a value in the low single digits for a sharp result, or use Constraint Quality if you need a hard size ceiling instead.
What the Output File Actually Contains
| Property | Value for this conversion |
|---|---|
| Container | FLV (Flash Video) |
| Video codec | Sorenson Spark by default; H.264, Flash Screen Video or Flash Screen Video 2 if selected |
| Audio track | None — a photo carries no sound, so the audio options are hidden and the clip is silent |
| Frame rate | 1 fps, B-frames disabled |
| Default clip length | 5 seconds per image |
| Colour handling | Sorenson Spark and H.264 encode 4:2:0; the two Flash Screen Video codecs store RGB losslessly |
| Frame size | Keep original by default; Video resolution offers presets, percentages and explicit Width × Height |
| Letterbox fill | The Background Color option, white by default |
| Source handling | Each image is normalised and capped at 4096 px on its long edge before encoding |
Common Errors and How to Fix Them
- "The picture is blocky no matter which preset I choose." You are on the default Sorenson Spark codec with Quality Preset selected, which has nothing to compute a bitrate from. Switch to Constant Quality (try 2-6) or Constraint Quality with an explicit Max bitrate.
- "The file is enormous." You picked Flash Video or Flash Video (v2). Both are lossless screen codecs, so rate control is bypassed and every pixel is stored. Use FLV or H.264 for photographic content.
- "My browser won't play it." No browser has played Flash content since Adobe's block took effect on 12 January 2021. VLC and any ffmpeg-based player still decode FLV files directly; for a web-embeddable file, convert to MP4.
- "There is no sound." Expected — the source is a photograph, so no audio stream is created.
- "White bars appear around my photo." The image's aspect ratio does not match the chosen frame, and the gap is filled with the Background Color, which defaults to white.
- "The upload server rejected the codec." Some media servers only accept H.264 inside FLV. Re-convert with Video Codec set to H.264 rather than the default.
When This Doesn't Work
If the goal is a video anyone can watch, FLV is the wrong container in 2026 — the plugin it depended on has been end-of-life since 31 December 2020, and Adobe recommends uninstalling Flash Player outright. Use JPG to MP4 for a file that plays in every browser, phone and TV. FLV remains a reasonable target in exactly two situations: an old CMS, LMS or media server whose uploader only accepts .flv, and RTMP-based ingest workflows, which still package audio and video in FLV-style tags. If you have inherited FLV files that need modernising, FLV to MP4 goes the other way.
Frequently Asked Questions
Which codec does the FLV use by default?
Sorenson Spark — the codec ffmpeg identifies as "FLV / Sorenson Spark / Sorenson H.263 (Flash Video)". It is the classic Flash Video codec and the most broadly compatible choice for genuinely old software. It encodes 4:2:0 only.
Can I put H.264 inside an FLV file?
Yes. Select H.264 in the Video Codec list. The FLV container carries AVC perfectly well, this is what most media servers expect today, and it unlocks the CRF-based quality controls that Sorenson Spark does not support.
Why does the Quality Preset appear to do nothing?
On codecs without CRF — which includes Sorenson Spark — the preset scales the source file's video bitrate instead. A still photo reports a video bitrate of zero, so the computed target collapses and the encoder falls back to its own minimum. Constant Quality and Constraint Quality both work on this codec; use one of them.
What are the "Flash Video" and "Flash Video (v2)" options for?
They are Flash Screen Video and Flash Screen Video 2, lossless codecs designed for screencasts. They store RGB pixels rather than subsampled colour, so text and flat UI stay razor sharp — and the files get very large, because our pipeline skips rate control entirely for lossless codecs. They are the wrong choice for photographs.
Does the FLV have an audio track?
No. There is nothing to encode from a JPG, so no audio stream is created and the audio controls are hidden on this page.
Can anything still play an FLV file?
Yes — just not Flash Player. VLC, MPV and anything built on ffmpeg decode FLV natively, and media servers still ingest it. Only the browser plugin is dead: Adobe stopped supporting Flash Player on 31 December 2020 and blocked content from running in it on 12 January 2021.
How long is the clip, and how do I change it?
Five seconds per image by default. The Duration dropdown covers a single frame at 60fps through to 10 seconds per image, and total length is that value multiplied by the number of images you merged.
Can I build a slideshow from several photos?
Yes. Add the images in order and leave Merge strategy on "Merge images" — each is held for the Duration you chose and they are concatenated into one FLV. "Video per image" produces one file per photo instead.
Why is FLV still around if Flash is gone?
Because the container outlived the player. RTMP ingest — still the standard way encoders push live feeds to streaming platforms — carries media in FLV-style tags, and a long tail of learning-management systems, video CMSes and archive tooling was written against .flv uploads and never rewritten.
What happens to my uploaded file?
Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared or made public.