GIF is a palette of at most 256 colours, all-or-nothing transparency, and animation. FLV is the Flash Video container, orphaned the day the plugin that gave it a name was switched off. ffmpeg sits between the two, and this page says exactly what happens to a GIF file on the way to becoming an FLV one.
What runs when a GIF file becomes FLV
ffmpeg held to a single thread, on a machine we rent and watch. Your GIF file is uploaded once, ffmpeg runs once, the FLV comes back, and neither file is kept. GIF to FLV is one of the 3649 pairs that engine was probed on with a real file, which is why it has a page here and why the pairs the probe could not prove do not.
What survives from the GIF into the FLV
The aspect ratio of the GIF. The engine scales to the smaller of 1280 pixels and the source width, and lets the height follow, rounded to an even number because encoders working in 4:2:0 refuse an odd one. A GIF already 1280 pixels wide or narrower is not resized at all.
Nothing you had as sound, because a GIF has none: the format carries no audio track at all. The FLV that comes out is SILENT, and that is worth knowing before you publish it somewhere that expects sound.
The running time and the order of the frames. ffmpeg re-encodes the GIF, it does not re-cut it, so the FLV starts and ends where the GIF did.
What GIF to FLV costs you
Every pixel, one more time. The GIF is decoded to raw frames and re-encoded as FLV, so whatever the GIF had already lost stays lost and this pass adds its own on top. Run one file through the loop four or five times and the damage is visible without looking for it.
Any width past 1280 pixels. The engine scales the GIF down to 1280 because encoder cost grows with pixel count: a 4K source costs about sixteen times a 1080p one, for an FLV nobody asked to be that big. Below that width nothing is touched.
Subtitle and data tracks. ffmpeg passes -sn and -dn on the way into the FLV, because most of them do not fit the container and a mux that fails on a subtitle would waste a picture that converted perfectly well.
Anything past 120 seconds of GIF. ffprobe measures the duration before the encoder starts, and a longer GIF comes back as a refusal in under a second rather than as a timeout four minutes later.
If a model is going to read the FLV
Nothing about GIF to FLV helps a language model, and pretending otherwise would be a sales line rather than a fact. An FLV is pixels and sound, both expensive to read and neither of them text. If what you actually want is what is said in the GIF, the useful move is not FLV at all: pull the audio out as MP3, which costs half a credit and comes back in about a second, and have that transcribed.
Running GIF to FLV against the real engine with a real file, ffmpeg wrote 174,055 bytes of FLV in 0.2 seconds, machine otherwise idle. That is one GIF file on one day and not an average, which is why the number is given together with the file that produced it.
The GIF to FLV verdict was reached by ffprobe, meaning the container was actually demultiplexed, recognised under the right name, and carried at least one stream. Which check was used matters, because they do not all prove the same thing, and a status code of 200 proves nothing whatsoever about whether the FLV file has anything inside it.
The same GIF file, sent somewhere else
Other outputs the probe measured out of a GIF file, so the cost of choosing FLV can be read against something. Sizes do not compare across engines, because each family was probed with its own GIF witness file.
GIF to PDF: 1,092,578 bytes in 0.9 seconds, verified by a format signature.
GIF to JPG: 20,559 bytes in under a tenth of a second, verified by a format signature.
GIF to PNG: 3,894 bytes in under a tenth of a second, verified by a format signature.
GIF to TIFF: 848,536 bytes in 0.2 seconds, verified by a format signature.
GIF to MP4: 54,682 bytes in 0.3 seconds, verified by ffprobe.
GIF to WEBM: 49,644 bytes in 2.0 seconds, verified by ffprobe.
Other ways into FLV, and what they measured
Among the published routes into FLV, GIF is the sixth largest output of the 9 measured. The witness files differ, so this ranks the probe run and not your document.
MKV to FLV: 177,042 bytes in 0.2 seconds.
MOV to FLV: 177,109 bytes in 0.2 seconds.
MPG to FLV: 177,342 bytes in 0.2 seconds.
WEBM to FLV: 169,113 bytes in 0.2 seconds.
WMV to FLV: 168,618 bytes in 0.2 seconds.
What we will not pretend about GIF to FLV
A GIF file over 150 MB is refused before the upload finishes rather than after it, so you do not wait for a rejection.
A GIF to FLV run that passes 240 seconds is killed, and the ffmpeg process is killed with it. A run left behind would sit on one of the machine's two cores until somebody noticed.
The GIF file behind the measurement on this page was 3 seconds of 320 by 240 test pattern at 25 frames a second, with a sine wave on the audio track, built by ffmpeg for the probe itself. That is why GIF to FLV came out at 0.2 seconds, and it is not what your file will do. The measurement proves the pair works and says almost nothing about how long yours will take.
Video is the one thing on this site that genuinely costs machine time, and the cost swings by two orders of magnitude with the encoder the container asks for: on this machine one minute of 720p source came out as AVI in 8.4 seconds and as WebM in 87, and the same minute in 1080p took 104. Expect an FLV to cost somewhere between a fraction of the GIF running time and twice it, not the tenth of a second the probe file took.
A GIF longer than 120 seconds is refused before any encoding starts, with an answer that names both limits, 150 MB and 120 seconds. It is not an upsell: two minutes of FLV encoding is roughly two minutes of the only machine there is, and the live traffic shares the same two cores.
GIF to FLV is the single conversion here that is not charged at the floor rate. It costs 2 credits per minute of GIF, every started minute counts, and because the engine refuses past 120 seconds one GIF to FLV run can never cost more than 4 credits. The figure is on the button before you press it.
One FLV encode at a time, and that was measured before it was decided. Two simultaneous transcodes do fit in memory, about 320 MB each, but each one goes from 104 seconds to 189: this machine is short of processor, not of memory, so throughput gains ten percent while the wait doubles. GIF to FLV therefore queues on a single slot and gives up after 25 seconds rather than piling up.
Nothing here reads what is inside the GIF. No transcription, no scene detection, no summary: GIF to FLV is a container and codec operation, and the FLV says exactly what the GIF said, in a different wrapper. The picture is the whole payload.
One GIF file at a time, chosen in the browser. There is nothing else to set up and nothing else on offer.
GIF to FLV: what people ask
What actually converts my GIF file to FLV?
ffmpeg does it, held to a single thread, on a machine we rent and watch. Not a browser trick and not somebody else service: the GIF file is uploaded once, ffmpeg runs once, the FLV comes back, and neither file is kept afterwards.
How long does GIF to FLV take?
The probe measured 0.2 seconds for 174,055 bytes of FLV, on a 3 second test pattern, and that number is honest about the plumbing and useless about your file. A video target re-encodes every frame: budget somewhere between a fraction of the GIF running time and twice it. The GIF is refused past 120 seconds, so the worst case is bounded.
What do I lose going from GIF to FLV?
The one to know about first: Every pixel, one more time. The GIF is decoded to raw frames and re-encoded as FLV, so whatever the GIF had already lost stays lost and this pass adds its own on top. Run one file through the loop four or five times and the damage is visible without looking for it.
Why did my FLV come back narrower than the GIF?
Because the engine caps every video output at 1280 pixels wide. Encoder cost grows with pixel count, and a 4K GIF would cost about sixteen times a 1080p one on a machine that also serves everybody else. A GIF at or below 1280 pixels comes back at its own size, untouched.
Is GIF to FLV free?
There is a free allowance every month, and GIF to FLV is the one conversion here that is not charged at the floor rate: 2 credits per minute of GIF, every started minute counted, capped at 4 credits because the engine refuses past 120 seconds. Re-encoding an FLV costs real machine time, so it is priced on the time it costs. The number is shown before you press anything.